Adds the encoding module to giflib.

Change-Id: Ia175f09ca16a1a57e821db8d54f755c6a7c143ba

4 files changed, 1595 insertions, 2 deletions

diff --git a/Android.mk b/Android.mk
index f9ff34b..427c1ee 100644
--- a/Android.mk
+++ b/Android.mk
@@ -5,10 +5,13 @@ LOCAL_SDK_VERSION := 9
 
 LOCAL_SRC_FILES := \
 	dgif_lib.c \
+	egif_lib.c \
 	gifalloc.c \
-	gif_err.c
+	gif_err.c \
+	gif_hash.c \
+	quantize.c
 
-LOCAL_CFLAGS += -Wno-format -DHAVE_CONFIG_H
+LOCAL_CFLAGS += -Wno-format -Wno-sign-compare -Wno-unused-parameter -DHAVE_CONFIG_H
 LOCAL_SDK_VERSION := 8
 LOCAL_MODULE:= libgif
 
diff --git a/egif_lib.c b/egif_lib.c
new file mode 100644
index 0000000..4e353ba
--- /dev/null
+++ b/egif_lib.c
@@ -0,0 +1,1149 @@
+/******************************************************************************
+
+egif_lib.c - GIF encoding
+
+The functions here and in dgif_lib.c are partitioned carefully so that
+if you only require one of read and write capability, only one of these
+two modules will be linked.  Preserve this property!
+
+*****************************************************************************/
+
+#include <unistd.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+
+#ifdef _WIN32
+#include <io.h>
+#else
+#include <sys/types.h>
+#endif /* _WIN32 */
+#include <sys/stat.h>
+
+#include "gif_lib.h"
+#include "gif_lib_private.h"
+
+/* Masks given codes to BitsPerPixel, to make sure all codes are in range: */
+/*@+charint@*/
+static const GifPixelType CodeMask[] = {
+    0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff
+};
+/*@-charint@*/
+
+static int EGifPutWord(int Word, GifFileType * GifFile);
+static int EGifSetupCompress(GifFileType * GifFile);
+static int EGifCompressLine(GifFileType * GifFile, GifPixelType * Line,
+                            int LineLen);
+static int EGifCompressOutput(GifFileType * GifFile, int Code);
+static int EGifBufferedOutput(GifFileType * GifFile, GifByteType * Buf,
+                              int c);
+
+/* extract bytes from an unsigned word */
+#define LOBYTE(x)	((x) & 0xff)
+#define HIBYTE(x)	(((x) >> 8) & 0xff)
+
+/******************************************************************************
+ Open a new GIF file for write, specified by name. If TestExistance then
+ if the file exists this routines fails (returns NULL).
+ Returns a dynamically allocated GifFileType pointer which serves as the GIF
+ info record. The Error member is cleared if successful.
+******************************************************************************/
+GifFileType *
+EGifOpenFileName(const char *FileName, const bool TestExistence, int *Error)
+{
+
+    int FileHandle;
+    GifFileType *GifFile;
+
+    if (TestExistence)
+        /* android-changed: changed "S_IREAD | S_IWRITE" to "S_IRUSR | S_IWUSR" */
+        FileHandle = open(FileName, O_WRONLY | O_CREAT | O_EXCL,
+                          S_IRUSR | S_IWUSR);
+    else
+        /* android-changed: changed "S_IREAD | S_IWRITE" to "S_IRUSR | S_IWUSR" */
+        FileHandle = open(FileName, O_WRONLY | O_CREAT | O_TRUNC,
+                          S_IRUSR | S_IWUSR);
+
+    if (FileHandle == -1) {
+        if (Error != NULL)
+	    *Error = E_GIF_ERR_OPEN_FAILED;
+        return NULL;
+    }
+    GifFile = EGifOpenFileHandle(FileHandle, Error);
+    if (GifFile == (GifFileType *) NULL)
+        (void)close(FileHandle);
+    return GifFile;
+}
+
+/******************************************************************************
+ Update a new GIF file, given its file handle, which must be opened for
+ write in binary mode.
+ Returns dynamically allocated a GifFileType pointer which serves as the GIF
+ info record.
+ Only fails on a memory allocation error.
+******************************************************************************/
+GifFileType *
+EGifOpenFileHandle(const int FileHandle, int *Error)
+{
+    GifFileType *GifFile;
+    GifFilePrivateType *Private;
+    FILE *f;
+
+    GifFile = (GifFileType *) malloc(sizeof(GifFileType));
+    if (GifFile == NULL) {
+        return NULL;
+    }
+
+    memset(GifFile, '\0', sizeof(GifFileType));
+
+    Private = (GifFilePrivateType *)malloc(sizeof(GifFilePrivateType));
+    if (Private == NULL) {
+        free(GifFile);
+        if (Error != NULL)
+	    *Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+        return NULL;
+    }
+    if ((Private->HashTable = _InitHashTable()) == NULL) {
+        free(GifFile);
+        free(Private);
+        if (Error != NULL)
+	    *Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+        return NULL;
+    }
+
+#ifdef _WIN32
+    _setmode(FileHandle, O_BINARY);    /* Make sure it is in binary mode. */
+#endif /* _WIN32 */
+
+    f = fdopen(FileHandle, "wb");    /* Make it into a stream: */
+
+    GifFile->Private = (void *)Private;
+    Private->FileHandle = FileHandle;
+    Private->File = f;
+    Private->FileState = FILE_STATE_WRITE;
+
+    Private->Write = (OutputFunc) 0;    /* No user write routine (MRB) */
+    GifFile->UserData = (void *)NULL;    /* No user write handle (MRB) */
+
+    GifFile->Error = 0;
+
+    return GifFile;
+}
+
+/******************************************************************************
+ Output constructor that takes user supplied output function.
+ Basically just a copy of EGifOpenFileHandle. (MRB)
+******************************************************************************/
+GifFileType *
+EGifOpen(void *userData, OutputFunc writeFunc, int *Error)
+{
+    GifFileType *GifFile;
+    GifFilePrivateType *Private;
+
+    GifFile = (GifFileType *)malloc(sizeof(GifFileType));
+    if (GifFile == NULL) {
+        if (Error != NULL)
+	    *Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+        return NULL;
+    }
+
+    memset(GifFile, '\0', sizeof(GifFileType));
+
+    Private = (GifFilePrivateType *)malloc(sizeof(GifFilePrivateType));
+    if (Private == NULL) {
+        free(GifFile);
+        if (Error != NULL)
+	    *Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+        return NULL;
+    }
+
+    Private->HashTable = _InitHashTable();
+    if (Private->HashTable == NULL) {
+        free (GifFile);
+        free (Private);
+        if (Error != NULL)
+	    *Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+        return NULL;
+    }
+
+    GifFile->Private = (void *)Private;
+    Private->FileHandle = 0;
+    Private->File = (FILE *) 0;
+    Private->FileState = FILE_STATE_WRITE;
+
+    Private->Write = writeFunc;    /* User write routine (MRB) */
+    GifFile->UserData = userData;    /* User write handle (MRB) */
+
+    Private->gif89 = false;	/* initially, write GIF87 */
+
+    GifFile->Error = 0;
+
+    return GifFile;
+}
+
+/******************************************************************************
+ Routine to compute the GIF version that will be written on output.
+******************************************************************************/
+char *
+EGifGetGifVersion(GifFileType *GifFile)
+{
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+    int i, j;
+
+    /* 
+     * Bulletproofing - always write GIF89 if we need to.
+     * Note, we don't clear the gif89 flag here because
+     * users of the sequential API might have called EGifSetGifVersion()
+     * in order to set that flag.
+     */
+    for (i = 0; i < GifFile->ImageCount; i++) {
+        for (j = 0; j < GifFile->SavedImages[i].ExtensionBlockCount; j++) {
+            int function =
+               GifFile->SavedImages[i].ExtensionBlocks[j].Function;
+
+            if (function == COMMENT_EXT_FUNC_CODE
+                || function == GRAPHICS_EXT_FUNC_CODE
+                || function == PLAINTEXT_EXT_FUNC_CODE
+                || function == APPLICATION_EXT_FUNC_CODE)
+                Private->gif89 = true;
+        }
+    }
+    for (i = 0; i < GifFile->ExtensionBlockCount; i++) {
+	int function = GifFile->ExtensionBlocks[i].Function;
+
+	if (function == COMMENT_EXT_FUNC_CODE
+	    || function == GRAPHICS_EXT_FUNC_CODE
+	    || function == PLAINTEXT_EXT_FUNC_CODE
+	    || function == APPLICATION_EXT_FUNC_CODE)
+	    Private->gif89 = true;
+    }
+ 
+    if (Private->gif89)
+	return GIF89_STAMP;
+    else
+	return GIF87_STAMP;
+}
+
+/******************************************************************************
+ Set the GIF version. In the extremely unlikely event that there is ever
+ another version, replace the bool argument with an enum in which the 
+ GIF87 value is 0 (numerically the same as bool false) and the GIF89 value
+ is 1 (numerically the same as bool true).  That way we'll even preserve
+ object-file compatibility!
+******************************************************************************/
+void EGifSetGifVersion(GifFileType *GifFile, const bool gif89)
+{
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+
+    Private->gif89 = gif89;
+}
+
+/******************************************************************************
+ All writes to the GIF should go through this.
+******************************************************************************/
+static int InternalWrite(GifFileType *GifFileOut, 
+		   const unsigned char *buf, size_t len)
+{
+    GifFilePrivateType *Private = (GifFilePrivateType*)GifFileOut->Private;
+    if (Private->Write)
+	return Private->Write(GifFileOut,buf,len);
+    else
+	return fwrite(buf, 1, len, Private->File);
+}
+
+/******************************************************************************
+ This routine should be called before any other EGif calls, immediately
+ following the GIF file opening.
+******************************************************************************/
+int
+EGifPutScreenDesc(GifFileType *GifFile,
+                  const int Width,
+                  const int Height,
+                  const int ColorRes,
+                  const int BackGround,
+                  const ColorMapObject *ColorMap)
+{
+    GifByteType Buf[3];
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+    char *write_version;
+
+    if (Private->FileState & FILE_STATE_SCREEN) {
+        /* If already has screen descriptor - something is wrong! */
+        GifFile->Error = E_GIF_ERR_HAS_SCRN_DSCR;
+        return GIF_ERROR;
+    }
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    write_version = EGifGetGifVersion(GifFile);
+
+    /* First write the version prefix into the file. */
+    if (InternalWrite(GifFile, (unsigned char *)write_version,
+              strlen(write_version)) != strlen(write_version)) {
+        GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+        return GIF_ERROR;
+    }
+
+    GifFile->SWidth = Width;
+    GifFile->SHeight = Height;
+    GifFile->SColorResolution = ColorRes;
+    GifFile->SBackGroundColor = BackGround;
+    if (ColorMap) {
+        GifFile->SColorMap = GifMakeMapObject(ColorMap->ColorCount,
+                                           ColorMap->Colors);
+        if (GifFile->SColorMap == NULL) {
+            GifFile->Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+            return GIF_ERROR;
+        }
+    } else
+        GifFile->SColorMap = NULL;
+
+    /*
+     * Put the logical screen descriptor into the file:
+     */
+    /* Logical Screen Descriptor: Dimensions */
+    (void)EGifPutWord(Width, GifFile);
+    (void)EGifPutWord(Height, GifFile);
+
+    /* Logical Screen Descriptor: Packed Fields */
+    /* Note: We have actual size of the color table default to the largest
+     * possible size (7+1 == 8 bits) because the decoder can use it to decide
+     * how to display the files.
+     */
+    Buf[0] = (ColorMap ? 0x80 : 0x00) | /* Yes/no global colormap */
+             ((ColorRes - 1) << 4) | /* Bits allocated to each primary color */
+        (ColorMap ? ColorMap->BitsPerPixel - 1 : 0x07 ); /* Actual size of the
+                                                            color table. */
+    if (ColorMap != NULL && ColorMap->SortFlag)
+	Buf[0] |= 0x08;
+    Buf[1] = BackGround;    /* Index into the ColorTable for background color */
+    Buf[2] = GifFile->AspectByte;     /* Pixel Aspect Ratio */
+    InternalWrite(GifFile, Buf, 3);
+
+    /* If we have Global color map - dump it also: */
+    if (ColorMap != NULL) {
+	int i;
+        for (i = 0; i < ColorMap->ColorCount; i++) {
+            /* Put the ColorMap out also: */
+            Buf[0] = ColorMap->Colors[i].Red;
+            Buf[1] = ColorMap->Colors[i].Green;
+            Buf[2] = ColorMap->Colors[i].Blue;
+            if (InternalWrite(GifFile, Buf, 3) != 3) {
+                GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+                return GIF_ERROR;
+            }
+        }
+    }
+
+    /* Mark this file as has screen descriptor, and no pixel written yet: */
+    Private->FileState |= FILE_STATE_SCREEN;
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ This routine should be called before any attempt to dump an image - any
+ call to any of the pixel dump routines.
+******************************************************************************/
+int
+EGifPutImageDesc(GifFileType *GifFile,
+                 const int Left,
+                 const int Top,
+                 const int Width,
+                 const int Height,
+                 const bool Interlace,
+                 const ColorMapObject *ColorMap)
+{
+    GifByteType Buf[3];
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (Private->FileState & FILE_STATE_IMAGE &&
+        Private->PixelCount > 0xffff0000UL) {
+        /* If already has active image descriptor - something is wrong! */
+        GifFile->Error = E_GIF_ERR_HAS_IMAG_DSCR;
+        return GIF_ERROR;
+    }
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+    GifFile->Image.Left = Left;
+    GifFile->Image.Top = Top;
+    GifFile->Image.Width = Width;
+    GifFile->Image.Height = Height;
+    GifFile->Image.Interlace = Interlace;
+    if (ColorMap) {
+        GifFile->Image.ColorMap = GifMakeMapObject(ColorMap->ColorCount,
+                                                ColorMap->Colors);
+        if (GifFile->Image.ColorMap == NULL) {
+            GifFile->Error = E_GIF_ERR_NOT_ENOUGH_MEM;
+            return GIF_ERROR;
+        }
+    } else {
+        GifFile->Image.ColorMap = NULL;
+    }
+
+    /* Put the image descriptor into the file: */
+    Buf[0] = DESCRIPTOR_INTRODUCER;    /* Image separator character. */
+    InternalWrite(GifFile, Buf, 1);
+    (void)EGifPutWord(Left, GifFile);
+    (void)EGifPutWord(Top, GifFile);
+    (void)EGifPutWord(Width, GifFile);
+    (void)EGifPutWord(Height, GifFile);
+    Buf[0] = (ColorMap ? 0x80 : 0x00) |
+       (Interlace ? 0x40 : 0x00) |
+       (ColorMap ? ColorMap->BitsPerPixel - 1 : 0);
+    InternalWrite(GifFile, Buf, 1);
+
+    /* If we have Global color map - dump it also: */
+    if (ColorMap != NULL) {
+	int i;
+        for (i = 0; i < ColorMap->ColorCount; i++) {
+            /* Put the ColorMap out also: */
+            Buf[0] = ColorMap->Colors[i].Red;
+            Buf[1] = ColorMap->Colors[i].Green;
+            Buf[2] = ColorMap->Colors[i].Blue;
+            if (InternalWrite(GifFile, Buf, 3) != 3) {
+                GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+                return GIF_ERROR;
+            }
+        }
+    }
+    if (GifFile->SColorMap == NULL && GifFile->Image.ColorMap == NULL) {
+        GifFile->Error = E_GIF_ERR_NO_COLOR_MAP;
+        return GIF_ERROR;
+    }
+
+    /* Mark this file as has screen descriptor: */
+    Private->FileState |= FILE_STATE_IMAGE;
+    Private->PixelCount = (long)Width *(long)Height;
+
+    /* Reset compress algorithm parameters. */
+    (void)EGifSetupCompress(GifFile);
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Put one full scanned line (Line) of length LineLen into GIF file.
+******************************************************************************/
+int
+EGifPutLine(GifFileType * GifFile, GifPixelType *Line, int LineLen)
+{
+    int i;
+    GifPixelType Mask;
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    if (!LineLen)
+        LineLen = GifFile->Image.Width;
+    if (Private->PixelCount < (unsigned)LineLen) {
+        GifFile->Error = E_GIF_ERR_DATA_TOO_BIG;
+        return GIF_ERROR;
+    }
+    Private->PixelCount -= LineLen;
+
+    /* Make sure the codes are not out of bit range, as we might generate
+     * wrong code (because of overflow when we combine them) in this case: */
+    Mask = CodeMask[Private->BitsPerPixel];
+    for (i = 0; i < LineLen; i++)
+        Line[i] &= Mask;
+
+    return EGifCompressLine(GifFile, Line, LineLen);
+}
+
+/******************************************************************************
+ Put one pixel (Pixel) into GIF file.
+******************************************************************************/
+int
+EGifPutPixel(GifFileType *GifFile, GifPixelType Pixel)
+{
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    if (Private->PixelCount == 0) {
+        GifFile->Error = E_GIF_ERR_DATA_TOO_BIG;
+        return GIF_ERROR;
+    }
+    --Private->PixelCount;
+
+    /* Make sure the code is not out of bit range, as we might generate
+     * wrong code (because of overflow when we combine them) in this case: */
+    Pixel &= CodeMask[Private->BitsPerPixel];
+
+    return EGifCompressLine(GifFile, &Pixel, 1);
+}
+
+/******************************************************************************
+ Put a comment into GIF file using the GIF89 comment extension block.
+******************************************************************************/
+int
+EGifPutComment(GifFileType *GifFile, const char *Comment)
+{
+    unsigned int length = strlen(Comment);
+    char *buf;
+
+    length = strlen(Comment);
+    if (length <= 255) {
+        return EGifPutExtension(GifFile, COMMENT_EXT_FUNC_CODE,
+                                length, Comment);
+    } else {
+        buf = (char *)Comment;
+        if (EGifPutExtensionLeader(GifFile, COMMENT_EXT_FUNC_CODE)
+                == GIF_ERROR) {
+            return GIF_ERROR;
+        }
+
+        /* Break the comment into 255 byte sub blocks */
+        while (length > 255) {
+            if (EGifPutExtensionBlock(GifFile, 255, buf) == GIF_ERROR) {
+                return GIF_ERROR;
+            }
+            buf = buf + 255;
+            length -= 255;
+        }
+        /* Output any partial block and the clear code. */
+        if (length > 0) {
+            if (EGifPutExtensionBlock(GifFile, length, buf) == GIF_ERROR) {
+                return GIF_ERROR;
+            }
+        }
+	if (EGifPutExtensionTrailer(GifFile) == GIF_ERROR) {
+	    return GIF_ERROR;
+        }
+    }
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Begin an extension block (see GIF manual).  More
+ extensions can be dumped using EGifPutExtensionBlock until
+ EGifPutExtensionTrailer is invoked.
+******************************************************************************/
+int
+EGifPutExtensionLeader(GifFileType *GifFile, const int ExtCode)
+{
+    GifByteType Buf[3];
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    Buf[0] = EXTENSION_INTRODUCER;
+    Buf[1] = ExtCode;
+    InternalWrite(GifFile, Buf, 2);
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Put extension block data (see GIF manual) into a GIF file.
+******************************************************************************/
+int
+EGifPutExtensionBlock(GifFileType *GifFile, 
+		     const int ExtLen,
+		     const void *Extension)
+{
+    GifByteType Buf;
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    Buf = ExtLen;
+    InternalWrite(GifFile, &Buf, 1);
+    InternalWrite(GifFile, Extension, ExtLen);
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Put a terminating block (see GIF manual) into a GIF file.
+******************************************************************************/
+int
+EGifPutExtensionTrailer(GifFileType *GifFile) {
+
+    GifByteType Buf;
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    /* Write the block terminator */
+    Buf = 0;
+    InternalWrite(GifFile, &Buf, 1);
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Put an extension block (see GIF manual) into a GIF file.
+ Warning: This function is only useful for Extension blocks that have at
+ most one subblock.  Extensions with more than one subblock need to use the
+ EGifPutExtension{Leader,Block,Trailer} functions instead.
+******************************************************************************/
+int
+EGifPutExtension(GifFileType *GifFile,
+                 const int ExtCode,
+                 const int ExtLen,
+                 const void *Extension) {
+
+    GifByteType Buf[3];
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    if (ExtCode == 0)
+        InternalWrite(GifFile, (GifByteType *)&ExtLen, 1);
+    else {
+        Buf[0] = EXTENSION_INTRODUCER;
+        Buf[1] = ExtCode;   /* Extension Label */
+        Buf[2] = ExtLen;    /* Extension length */
+        InternalWrite(GifFile, Buf, 3);
+    }
+    InternalWrite(GifFile, Extension, ExtLen);
+    Buf[0] = 0;
+    InternalWrite(GifFile, Buf, 1);
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Render a Graphics Control Block as raw extension data
+******************************************************************************/
+
+size_t EGifGCBToExtension(const GraphicsControlBlock *GCB,
+		       GifByteType *GifExtension)
+{
+    GifExtension[0] = 0;
+    GifExtension[0] |= (GCB->TransparentColor == NO_TRANSPARENT_COLOR) ? 0x00 : 0x01;
+    GifExtension[0] |= GCB->UserInputFlag ? 0x02 : 0x00;
+    GifExtension[0] |= ((GCB->DisposalMode & 0x07) << 2);
+    GifExtension[1] = LOBYTE(GCB->DelayTime);
+    GifExtension[2] = HIBYTE(GCB->DelayTime);
+    GifExtension[3] = (char)GCB->TransparentColor;
+    return 4;
+}
+
+/******************************************************************************
+ Replace the Graphics Control Block for a saved image, if it exists.
+******************************************************************************/
+
+int EGifGCBToSavedExtension(const GraphicsControlBlock *GCB, 
+			    GifFileType *GifFile, int ImageIndex)
+{
+    int i;
+    size_t Len;
+    GifByteType buf[sizeof(GraphicsControlBlock)]; /* a bit dodgy... */
+
+    if (ImageIndex < 0 || ImageIndex > GifFile->ImageCount - 1)
+	return GIF_ERROR;
+
+    for (i = 0; i < GifFile->SavedImages[ImageIndex].ExtensionBlockCount; i++) {
+	ExtensionBlock *ep = &GifFile->SavedImages[ImageIndex].ExtensionBlocks[i];
+	if (ep->Function == GRAPHICS_EXT_FUNC_CODE) {
+	    EGifGCBToExtension(GCB, ep->Bytes);
+	    return GIF_OK;
+	}
+    }
+
+    Len = EGifGCBToExtension(GCB, (GifByteType *)buf);
+    if (GifAddExtensionBlock(&GifFile->SavedImages[ImageIndex].ExtensionBlockCount,
+			     &GifFile->SavedImages[ImageIndex].ExtensionBlocks,
+			     GRAPHICS_EXT_FUNC_CODE,
+			     Len,
+			     (unsigned char *)buf) == GIF_ERROR)
+	return (GIF_ERROR);
+
+    return (GIF_OK);
+}
+
+/******************************************************************************
+ Put the image code in compressed form. This routine can be called if the
+ information needed to be piped out as is. Obviously this is much faster
+ than decoding and encoding again. This routine should be followed by calls
+ to EGifPutCodeNext, until NULL block is given.
+ The block should NOT be freed by the user (not dynamically allocated).
+******************************************************************************/
+int
+EGifPutCode(GifFileType *GifFile, int CodeSize, const GifByteType *CodeBlock)
+{
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    /* No need to dump code size as Compression set up does any for us: */
+    /* 
+     * Buf = CodeSize;
+     * if (InternalWrite(GifFile, &Buf, 1) != 1) {
+     *      GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+     *      return GIF_ERROR;
+     * }
+     */
+
+    return EGifPutCodeNext(GifFile, CodeBlock);
+}
+
+/******************************************************************************
+ Continue to put the image code in compressed form. This routine should be
+ called with blocks of code as read via DGifGetCode/DGifGetCodeNext. If
+ given buffer pointer is NULL, empty block is written to mark end of code.
+******************************************************************************/
+int
+EGifPutCodeNext(GifFileType *GifFile, const GifByteType *CodeBlock)
+{
+    GifByteType Buf;
+    GifFilePrivateType *Private = (GifFilePrivateType *)GifFile->Private;
+
+    if (CodeBlock != NULL) {
+        if (InternalWrite(GifFile, CodeBlock, CodeBlock[0] + 1)
+               != (unsigned)(CodeBlock[0] + 1)) {
+            GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+            return GIF_ERROR;
+        }
+    } else {
+        Buf = 0;
+        if (InternalWrite(GifFile, &Buf, 1) != 1) {
+            GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+            return GIF_ERROR;
+        }
+        Private->PixelCount = 0;    /* And local info. indicate image read. */
+    }
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ This routine should be called last, to close the GIF file.
+******************************************************************************/
+int
+EGifCloseFile(GifFileType *GifFile)
+{
+    GifByteType Buf;
+    GifFilePrivateType *Private;
+    FILE *File;
+
+    if (GifFile == NULL)
+        return GIF_ERROR;
+
+    Private = (GifFilePrivateType *) GifFile->Private;
+    if (Private == NULL)
+	return GIF_ERROR;
+    if (!IS_WRITEABLE(Private)) {
+        /* This file was NOT open for writing: */
+        GifFile->Error = E_GIF_ERR_NOT_WRITEABLE;
+        return GIF_ERROR;
+    }
+
+    File = Private->File;
+
+    Buf = TERMINATOR_INTRODUCER;
+    InternalWrite(GifFile, &Buf, 1);
+
+    if (GifFile->Image.ColorMap) {
+        GifFreeMapObject(GifFile->Image.ColorMap);
+        GifFile->Image.ColorMap = NULL;
+    }
+    if (GifFile->SColorMap) {
+        GifFreeMapObject(GifFile->SColorMap);
+        GifFile->SColorMap = NULL;
+    }
+    if (Private) {
+        if (Private->HashTable) {
+            free((char *) Private->HashTable);
+        }
+	    free((char *) Private);
+    }
+
+    if (File && fclose(File) != 0) {
+        GifFile->Error = E_GIF_ERR_CLOSE_FAILED;
+        return GIF_ERROR;
+    }
+
+    /* 
+     * Without the #ifndef, we get spurious warnings because Coverity mistakenly
+     * thinks the GIF structure is freed on an error return. 
+     */
+#ifndef __COVERITY__
+    free(GifFile);
+#endif /* __COVERITY__ */
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Put 2 bytes (a word) into the given file in little-endian order:
+******************************************************************************/
+static int
+EGifPutWord(int Word, GifFileType *GifFile)
+{
+    unsigned char c[2];
+
+    c[0] = LOBYTE(Word);
+    c[1] = HIBYTE(Word);
+    if (InternalWrite(GifFile, c, 2) == 2)
+        return GIF_OK;
+    else
+        return GIF_ERROR;
+}
+
+/******************************************************************************
+ Setup the LZ compression for this image:
+******************************************************************************/
+static int
+EGifSetupCompress(GifFileType *GifFile)
+{
+    int BitsPerPixel;
+    GifByteType Buf;
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+
+    /* Test and see what color map to use, and from it # bits per pixel: */
+    if (GifFile->Image.ColorMap)
+        BitsPerPixel = GifFile->Image.ColorMap->BitsPerPixel;
+    else if (GifFile->SColorMap)
+        BitsPerPixel = GifFile->SColorMap->BitsPerPixel;
+    else {
+        GifFile->Error = E_GIF_ERR_NO_COLOR_MAP;
+        return GIF_ERROR;
+    }
+
+    Buf = BitsPerPixel = (BitsPerPixel < 2 ? 2 : BitsPerPixel);
+    InternalWrite(GifFile, &Buf, 1);    /* Write the Code size to file. */
+
+    Private->Buf[0] = 0;    /* Nothing was output yet. */
+    Private->BitsPerPixel = BitsPerPixel;
+    Private->ClearCode = (1 << BitsPerPixel);
+    Private->EOFCode = Private->ClearCode + 1;
+    Private->RunningCode = Private->EOFCode + 1;
+    Private->RunningBits = BitsPerPixel + 1;    /* Number of bits per code. */
+    Private->MaxCode1 = 1 << Private->RunningBits;    /* Max. code + 1. */
+    Private->CrntCode = FIRST_CODE;    /* Signal that this is first one! */
+    Private->CrntShiftState = 0;    /* No information in CrntShiftDWord. */
+    Private->CrntShiftDWord = 0;
+
+   /* Clear hash table and send Clear to make sure the decoder do the same. */
+    _ClearHashTable(Private->HashTable);
+
+    if (EGifCompressOutput(GifFile, Private->ClearCode) == GIF_ERROR) {
+        GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
+        return GIF_ERROR;
+    }
+    return GIF_OK;
+}
+
+/******************************************************************************
+ The LZ compression routine:
+ This version compresses the given buffer Line of length LineLen.
+ This routine can be called a few times (one per scan line, for example), in
+ order to complete the whole image.
+******************************************************************************/
+static int
+EGifCompressLine(GifFileType *GifFile,
+                 GifPixelType *Line,
+                 const int LineLen)
+{
+    int i = 0, CrntCode, NewCode;
+    unsigned long NewKey;
+    GifPixelType Pixel;
+    GifHashTableType *HashTable;
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+
+    HashTable = Private->HashTable;
+
+    if (Private->CrntCode == FIRST_CODE)    /* Its first time! */
+        CrntCode = Line[i++];
+    else
+        CrntCode = Private->CrntCode;    /* Get last code in compression. */
+
+    while (i < LineLen) {   /* Decode LineLen items. */
+        Pixel = Line[i++];  /* Get next pixel from stream. */
+        /* Form a new unique key to search hash table for the code combines 
+         * CrntCode as Prefix string with Pixel as postfix char.
+         */
+        NewKey = (((uint32_t) CrntCode) << 8) + Pixel;
+        if ((NewCode = _ExistsHashTable(HashTable, NewKey)) >= 0) {
+            /* This Key is already there, or the string is old one, so
+             * simple take new code as our CrntCode:
+             */
+            CrntCode = NewCode;
+        } else {
+            /* Put it in hash table, output the prefix code, and make our
+             * CrntCode equal to Pixel.
+             */
+            if (EGifCompressOutput(GifFile, CrntCode) == GIF_ERROR) {
+                GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
+                return GIF_ERROR;
+            }
+            CrntCode = Pixel;
+
+            /* If however the HashTable if full, we send a clear first and
+             * Clear the hash table.
+             */
+            if (Private->RunningCode >= LZ_MAX_CODE) {
+                /* Time to do some clearance: */
+                if (EGifCompressOutput(GifFile, Private->ClearCode)
+                        == GIF_ERROR) {
+                    GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
+                    return GIF_ERROR;
+                }
+                Private->RunningCode = Private->EOFCode + 1;
+                Private->RunningBits = Private->BitsPerPixel + 1;
+                Private->MaxCode1 = 1 << Private->RunningBits;
+                _ClearHashTable(HashTable);
+            } else {
+                /* Put this unique key with its relative Code in hash table: */
+                _InsertHashTable(HashTable, NewKey, Private->RunningCode++);
+            }
+        }
+
+    }
+
+    /* Preserve the current state of the compression algorithm: */
+    Private->CrntCode = CrntCode;
+
+    if (Private->PixelCount == 0) {
+        /* We are done - output last Code and flush output buffers: */
+        if (EGifCompressOutput(GifFile, CrntCode) == GIF_ERROR) {
+            GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
+            return GIF_ERROR;
+        }
+        if (EGifCompressOutput(GifFile, Private->EOFCode) == GIF_ERROR) {
+            GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
+            return GIF_ERROR;
+        }
+        if (EGifCompressOutput(GifFile, FLUSH_OUTPUT) == GIF_ERROR) {
+            GifFile->Error = E_GIF_ERR_DISK_IS_FULL;
+            return GIF_ERROR;
+        }
+    }
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ The LZ compression output routine:
+ This routine is responsible for the compression of the bit stream into
+ 8 bits (bytes) packets.
+ Returns GIF_OK if written successfully.
+******************************************************************************/
+static int
+EGifCompressOutput(GifFileType *GifFile,
+                   const int Code)
+{
+    GifFilePrivateType *Private = (GifFilePrivateType *) GifFile->Private;
+    int retval = GIF_OK;
+
+    if (Code == FLUSH_OUTPUT) {
+        while (Private->CrntShiftState > 0) {
+            /* Get Rid of what is left in DWord, and flush it. */
+            if (EGifBufferedOutput(GifFile, Private->Buf,
+                                 Private->CrntShiftDWord & 0xff) == GIF_ERROR)
+                retval = GIF_ERROR;
+            Private->CrntShiftDWord >>= 8;
+            Private->CrntShiftState -= 8;
+        }
+        Private->CrntShiftState = 0;    /* For next time. */
+        if (EGifBufferedOutput(GifFile, Private->Buf,
+                               FLUSH_OUTPUT) == GIF_ERROR)
+            retval = GIF_ERROR;
+    } else {
+        Private->CrntShiftDWord |= ((long)Code) << Private->CrntShiftState;
+        Private->CrntShiftState += Private->RunningBits;
+        while (Private->CrntShiftState >= 8) {
+            /* Dump out full bytes: */
+            if (EGifBufferedOutput(GifFile, Private->Buf,
+                                 Private->CrntShiftDWord & 0xff) == GIF_ERROR)
+                retval = GIF_ERROR;
+            Private->CrntShiftDWord >>= 8;
+            Private->CrntShiftState -= 8;
+        }
+    }
+
+    /* If code cannt fit into RunningBits bits, must raise its size. Note */
+    /* however that codes above 4095 are used for special signaling.      */
+    if (Private->RunningCode >= Private->MaxCode1 && Code <= 4095) {
+       Private->MaxCode1 = 1 << ++Private->RunningBits;
+    }
+
+    return retval;
+}
+
+/******************************************************************************
+ This routines buffers the given characters until 255 characters are ready
+ to be output. If Code is equal to -1 the buffer is flushed (EOF).
+ The buffer is Dumped with first byte as its size, as GIF format requires.
+ Returns GIF_OK if written successfully.
+******************************************************************************/
+static int
+EGifBufferedOutput(GifFileType *GifFile,
+                   GifByteType *Buf,
+                   int c)
+{
+    if (c == FLUSH_OUTPUT) {
+        /* Flush everything out. */
+        if (Buf[0] != 0
+            && InternalWrite(GifFile, Buf, Buf[0] + 1) != (unsigned)(Buf[0] + 1)) {
+            GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+            return GIF_ERROR;
+        }
+        /* Mark end of compressed data, by an empty block (see GIF doc): */
+        Buf[0] = 0;
+        if (InternalWrite(GifFile, Buf, 1) != 1) {
+            GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+            return GIF_ERROR;
+        }
+    } else {
+        if (Buf[0] == 255) {
+            /* Dump out this buffer - it is full: */
+            if (InternalWrite(GifFile, Buf, Buf[0] + 1) != (unsigned)(Buf[0] + 1)) {
+                GifFile->Error = E_GIF_ERR_WRITE_FAILED;
+                return GIF_ERROR;
+            }
+            Buf[0] = 0;
+        }
+        Buf[++Buf[0]] = c;
+    }
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ This routine writes to disk an in-core representation of a GIF previously
+ created by DGifSlurp().
+******************************************************************************/
+
+static int
+EGifWriteExtensions(GifFileType *GifFileOut, 
+			       ExtensionBlock *ExtensionBlocks, 
+			       int ExtensionBlockCount) 
+{
+    if (ExtensionBlocks) {
+        ExtensionBlock *ep;
+	int j;
+
+	for (j = 0; j < ExtensionBlockCount; j++) {
+	    ep = &ExtensionBlocks[j];
+	    if (ep->Function != CONTINUE_EXT_FUNC_CODE)
+		if (EGifPutExtensionLeader(GifFileOut, ep->Function) == GIF_ERROR)
+		    return (GIF_ERROR);
+	    if (EGifPutExtensionBlock(GifFileOut, ep->ByteCount, ep->Bytes) == GIF_ERROR)
+		return (GIF_ERROR);
+	    if (j == ExtensionBlockCount - 1 || (ep+1)->Function != CONTINUE_EXT_FUNC_CODE)
+		if (EGifPutExtensionTrailer(GifFileOut) == GIF_ERROR)
+		    return (GIF_ERROR);
+	}
+    }
+
+    return (GIF_OK);
+}
+
+int
+EGifSpew(GifFileType *GifFileOut) 
+{
+    int i, j; 
+
+    if (EGifPutScreenDesc(GifFileOut,
+                          GifFileOut->SWidth,
+                          GifFileOut->SHeight,
+                          GifFileOut->SColorResolution,
+                          GifFileOut->SBackGroundColor,
+                          GifFileOut->SColorMap) == GIF_ERROR) {
+        return (GIF_ERROR);
+    }
+
+    for (i = 0; i < GifFileOut->ImageCount; i++) {
+        SavedImage *sp = &GifFileOut->SavedImages[i];
+        int SavedHeight = sp->ImageDesc.Height;
+        int SavedWidth = sp->ImageDesc.Width;
+
+        /* this allows us to delete images by nuking their rasters */
+        if (sp->RasterBits == NULL)
+            continue;
+
+	if (EGifWriteExtensions(GifFileOut, 
+				sp->ExtensionBlocks,
+				sp->ExtensionBlockCount) == GIF_ERROR)
+	    return (GIF_ERROR);
+
+        if (EGifPutImageDesc(GifFileOut,
+                             sp->ImageDesc.Left,
+                             sp->ImageDesc.Top,
+                             SavedWidth,
+                             SavedHeight,
+                             sp->ImageDesc.Interlace,
+                             sp->ImageDesc.ColorMap) == GIF_ERROR)
+            return (GIF_ERROR);
+
+	if (sp->ImageDesc.Interlace) {
+	     /* 
+	      * The way an interlaced image should be written - 
+	      * offsets and jumps...
+	      */
+	    int InterlacedOffset[] = { 0, 4, 2, 1 };
+	    int InterlacedJumps[] = { 8, 8, 4, 2 };
+	    int k;
+	    /* Need to perform 4 passes on the images: */
+	    for (k = 0; k < 4; k++)
+		for (j = InterlacedOffset[k]; 
+		     j < SavedHeight;
+		     j += InterlacedJumps[k]) {
+		    if (EGifPutLine(GifFileOut, 
+				    sp->RasterBits + j * SavedWidth, 
+				    SavedWidth)	== GIF_ERROR)
+			return (GIF_ERROR);
+		}
+	} else {
+	    for (j = 0; j < SavedHeight; j++) {
+		if (EGifPutLine(GifFileOut,
+				sp->RasterBits + j * SavedWidth,
+				SavedWidth) == GIF_ERROR)
+		    return (GIF_ERROR);
+	    }
+	}
+    }
+
+    if (EGifWriteExtensions(GifFileOut,
+			    GifFileOut->ExtensionBlocks,
+			    GifFileOut->ExtensionBlockCount) == GIF_ERROR)
+	return (GIF_ERROR);
+
+    if (EGifCloseFile(GifFileOut) == GIF_ERROR)
+        return (GIF_ERROR);
+
+    return (GIF_OK);
+}
+
+/* end */
diff --git a/gif_hash.c b/gif_hash.c
new file mode 100644
index 0000000..61a4d13
--- /dev/null
+++ b/gif_hash.c
@@ -0,0 +1,132 @@
+/*****************************************************************************
+
+gif_hash.c -- module to support the following operations:
+
+1. InitHashTable - initialize hash table.
+2. ClearHashTable - clear the hash table to an empty state.
+2. InsertHashTable - insert one item into data structure.
+3. ExistsHashTable - test if item exists in data structure.
+
+This module is used to hash the GIF codes during encoding.
+
+*****************************************************************************/
+
+#include <unistd.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "gif_lib.h"
+#include "gif_hash.h"
+#include "gif_lib_private.h"
+
+/* #define  DEBUG_HIT_RATE    Debug number of misses per hash Insert/Exists. */
+
+#ifdef	DEBUG_HIT_RATE
+static long NumberOfTests = 0,
+	    NumberOfMisses = 0;
+#endif	/* DEBUG_HIT_RATE */
+
+static int KeyItem(uint32_t Item);
+
+/******************************************************************************
+ Initialize HashTable - allocate the memory needed and clear it.	      *
+******************************************************************************/
+GifHashTableType *_InitHashTable(void)
+{
+    GifHashTableType *HashTable;
+
+    if ((HashTable = (GifHashTableType *) malloc(sizeof(GifHashTableType)))
+	== NULL)
+	return NULL;
+
+    _ClearHashTable(HashTable);
+
+    return HashTable;
+}
+
+/******************************************************************************
+ Routine to clear the HashTable to an empty state.			      *
+ This part is a little machine depended. Use the commented part otherwise.   *
+******************************************************************************/
+void _ClearHashTable(GifHashTableType *HashTable)
+{
+    memset(HashTable -> HTable, 0xFF, HT_SIZE * sizeof(uint32_t));
+}
+
+/******************************************************************************
+ Routine to insert a new Item into the HashTable. The data is assumed to be  *
+ new one.								      *
+******************************************************************************/
+void _InsertHashTable(GifHashTableType *HashTable, uint32_t Key, int Code)
+{
+    int HKey = KeyItem(Key);
+    uint32_t *HTable = HashTable -> HTable;
+
+#ifdef DEBUG_HIT_RATE
+	NumberOfTests++;
+	NumberOfMisses++;
+#endif /* DEBUG_HIT_RATE */
+
+    while (HT_GET_KEY(HTable[HKey]) != 0xFFFFFL) {
+#ifdef DEBUG_HIT_RATE
+	    NumberOfMisses++;
+#endif /* DEBUG_HIT_RATE */
+	HKey = (HKey + 1) & HT_KEY_MASK;
+    }
+    HTable[HKey] = HT_PUT_KEY(Key) | HT_PUT_CODE(Code);
+}
+
+/******************************************************************************
+ Routine to test if given Key exists in HashTable and if so returns its code *
+ Returns the Code if key was found, -1 if not.				      *
+******************************************************************************/
+int _ExistsHashTable(GifHashTableType *HashTable, uint32_t Key)
+{
+    int HKey = KeyItem(Key);
+    uint32_t *HTable = HashTable -> HTable, HTKey;
+
+#ifdef DEBUG_HIT_RATE
+	NumberOfTests++;
+	NumberOfMisses++;
+#endif /* DEBUG_HIT_RATE */
+
+    while ((HTKey = HT_GET_KEY(HTable[HKey])) != 0xFFFFFL) {
+#ifdef DEBUG_HIT_RATE
+	    NumberOfMisses++;
+#endif /* DEBUG_HIT_RATE */
+	if (Key == HTKey) return HT_GET_CODE(HTable[HKey]);
+	HKey = (HKey + 1) & HT_KEY_MASK;
+    }
+
+    return -1;
+}
+
+/******************************************************************************
+ Routine to generate an HKey for the hashtable out of the given unique key.  *
+ The given Key is assumed to be 20 bits as follows: lower 8 bits are the     *
+ new postfix character, while the upper 12 bits are the prefix code.	      *
+ Because the average hit ratio is only 2 (2 hash references per entry),      *
+ evaluating more complex keys (such as twin prime keys) does not worth it!   *
+******************************************************************************/
+static int KeyItem(uint32_t Item)
+{
+    return ((Item >> 12) ^ Item) & HT_KEY_MASK;
+}
+
+#ifdef	DEBUG_HIT_RATE
+/******************************************************************************
+ Debugging routine to print the hit ratio - number of times the hash table   *
+ was tested per operation. This routine was used to test the KeyItem routine *
+******************************************************************************/
+void HashTablePrintHitRatio(void)
+{
+    printf("Hash Table Hit Ratio is %ld/%ld = %ld%%.\n",
+	NumberOfMisses, NumberOfTests,
+	NumberOfMisses * 100 / NumberOfTests);
+}
+#endif	/* DEBUG_HIT_RATE */
+
+/* end */
diff --git a/quantize.c b/quantize.c
new file mode 100644
index 0000000..fc31f36
--- /dev/null
+++ b/quantize.c
@@ -0,0 +1,309 @@
+/*****************************************************************************
+
+ quantize.c - quantize a high resolution image into lower one
+
+ Based on: "Color Image Quantization for frame buffer Display", by
+ Paul Heckbert SIGGRAPH 1982 page 297-307.
+
+ This doesn't really belong in the core library, was undocumented,
+ and was removed in 4.2.  Then it turned out some client apps were
+ actually using it, so it was restored in 5.0.
+
+******************************************************************************/
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "gif_lib.h"
+#include "gif_lib_private.h"
+
+#define ABS(x)    ((x) > 0 ? (x) : (-(x)))
+
+#define COLOR_ARRAY_SIZE 32768
+#define BITS_PER_PRIM_COLOR 5
+#define MAX_PRIM_COLOR      0x1f
+
+static int SortRGBAxis;
+
+typedef struct QuantizedColorType {
+    GifByteType RGB[3];
+    GifByteType NewColorIndex;
+    long Count;
+    struct QuantizedColorType *Pnext;
+} QuantizedColorType;
+
+typedef struct NewColorMapType {
+    GifByteType RGBMin[3], RGBWidth[3];
+    unsigned int NumEntries; /* # of QuantizedColorType in linked list below */
+    unsigned long Count; /* Total number of pixels in all the entries */
+    QuantizedColorType *QuantizedColors;
+} NewColorMapType;
+
+static int SubdivColorMap(NewColorMapType * NewColorSubdiv,
+                          unsigned int ColorMapSize,
+                          unsigned int *NewColorMapSize);
+static int SortCmpRtn(const void *Entry1, const void *Entry2);
+
+/******************************************************************************
+ Quantize high resolution image into lower one. Input image consists of a
+ 2D array for each of the RGB colors with size Width by Height. There is no
+ Color map for the input. Output is a quantized image with 2D array of
+ indexes into the output color map.
+   Note input image can be 24 bits at the most (8 for red/green/blue) and
+ the output has 256 colors at the most (256 entries in the color map.).
+ ColorMapSize specifies size of color map up to 256 and will be updated to
+ real size before returning.
+   Also non of the parameter are allocated by this routine.
+   This function returns GIF_OK if successful, GIF_ERROR otherwise.
+******************************************************************************/
+int
+GifQuantizeBuffer(unsigned int Width,
+               unsigned int Height,
+               int *ColorMapSize,
+               GifByteType * RedInput,
+               GifByteType * GreenInput,
+               GifByteType * BlueInput,
+               GifByteType * OutputBuffer,
+               GifColorType * OutputColorMap) {
+
+    unsigned int Index, NumOfEntries;
+    int i, j, MaxRGBError[3];
+    unsigned int NewColorMapSize;
+    long Red, Green, Blue;
+    NewColorMapType NewColorSubdiv[256];
+    QuantizedColorType *ColorArrayEntries, *QuantizedColor;
+
+    ColorArrayEntries = (QuantizedColorType *)malloc(
+                           sizeof(QuantizedColorType) * COLOR_ARRAY_SIZE);
+    if (ColorArrayEntries == NULL) {
+        return GIF_ERROR;
+    }
+
+    for (i = 0; i < COLOR_ARRAY_SIZE; i++) {
+        ColorArrayEntries[i].RGB[0] = i >> (2 * BITS_PER_PRIM_COLOR);
+        ColorArrayEntries[i].RGB[1] = (i >> BITS_PER_PRIM_COLOR) &
+           MAX_PRIM_COLOR;
+        ColorArrayEntries[i].RGB[2] = i & MAX_PRIM_COLOR;
+        ColorArrayEntries[i].Count = 0;
+    }
+
+    /* Sample the colors and their distribution: */
+    for (i = 0; i < (int)(Width * Height); i++) {
+        Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR)) <<
+                  (2 * BITS_PER_PRIM_COLOR)) +
+                ((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR)) <<
+                  BITS_PER_PRIM_COLOR) +
+                (BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR));
+        ColorArrayEntries[Index].Count++;
+    }
+
+    /* Put all the colors in the first entry of the color map, and call the
+     * recursive subdivision process.  */
+    for (i = 0; i < 256; i++) {
+        NewColorSubdiv[i].QuantizedColors = NULL;
+        NewColorSubdiv[i].Count = NewColorSubdiv[i].NumEntries = 0;
+        for (j = 0; j < 3; j++) {
+            NewColorSubdiv[i].RGBMin[j] = 0;
+            NewColorSubdiv[i].RGBWidth[j] = 255;
+        }
+    }
+
+    /* Find the non empty entries in the color table and chain them: */
+    for (i = 0; i < COLOR_ARRAY_SIZE; i++)
+        if (ColorArrayEntries[i].Count > 0)
+            break;
+    QuantizedColor = NewColorSubdiv[0].QuantizedColors = &ColorArrayEntries[i];
+    NumOfEntries = 1;
+    while (++i < COLOR_ARRAY_SIZE)
+        if (ColorArrayEntries[i].Count > 0) {
+            QuantizedColor->Pnext = &ColorArrayEntries[i];
+            QuantizedColor = &ColorArrayEntries[i];
+            NumOfEntries++;
+        }
+    QuantizedColor->Pnext = NULL;
+
+    NewColorSubdiv[0].NumEntries = NumOfEntries; /* Different sampled colors */
+    NewColorSubdiv[0].Count = ((long)Width) * Height; /* Pixels */
+    NewColorMapSize = 1;
+    if (SubdivColorMap(NewColorSubdiv, *ColorMapSize, &NewColorMapSize) !=
+       GIF_OK) {
+        free((char *)ColorArrayEntries);
+        return GIF_ERROR;
+    }
+    if (NewColorMapSize < *ColorMapSize) {
+        /* And clear rest of color map: */
+        for (i = NewColorMapSize; i < *ColorMapSize; i++)
+            OutputColorMap[i].Red = OutputColorMap[i].Green =
+                OutputColorMap[i].Blue = 0;
+    }
+
+    /* Average the colors in each entry to be the color to be used in the
+     * output color map, and plug it into the output color map itself. */
+    for (i = 0; i < NewColorMapSize; i++) {
+        if ((j = NewColorSubdiv[i].NumEntries) > 0) {
+            QuantizedColor = NewColorSubdiv[i].QuantizedColors;
+            Red = Green = Blue = 0;
+            while (QuantizedColor) {
+                QuantizedColor->NewColorIndex = i;
+                Red += QuantizedColor->RGB[0];
+                Green += QuantizedColor->RGB[1];
+                Blue += QuantizedColor->RGB[2];
+                QuantizedColor = QuantizedColor->Pnext;
+            }
+            OutputColorMap[i].Red = (Red << (8 - BITS_PER_PRIM_COLOR)) / j;
+            OutputColorMap[i].Green = (Green << (8 - BITS_PER_PRIM_COLOR)) / j;
+            OutputColorMap[i].Blue = (Blue << (8 - BITS_PER_PRIM_COLOR)) / j;
+        }
+    }
+
+    /* Finally scan the input buffer again and put the mapped index in the
+     * output buffer.  */
+    MaxRGBError[0] = MaxRGBError[1] = MaxRGBError[2] = 0;
+    for (i = 0; i < (int)(Width * Height); i++) {
+        Index = ((RedInput[i] >> (8 - BITS_PER_PRIM_COLOR)) <<
+                 (2 * BITS_PER_PRIM_COLOR)) +
+                ((GreenInput[i] >> (8 - BITS_PER_PRIM_COLOR)) <<
+                 BITS_PER_PRIM_COLOR) +
+                (BlueInput[i] >> (8 - BITS_PER_PRIM_COLOR));
+        Index = ColorArrayEntries[Index].NewColorIndex;
+        OutputBuffer[i] = Index;
+        if (MaxRGBError[0] < ABS(OutputColorMap[Index].Red - RedInput[i]))
+            MaxRGBError[0] = ABS(OutputColorMap[Index].Red - RedInput[i]);
+        if (MaxRGBError[1] < ABS(OutputColorMap[Index].Green - GreenInput[i]))
+            MaxRGBError[1] = ABS(OutputColorMap[Index].Green - GreenInput[i]);
+        if (MaxRGBError[2] < ABS(OutputColorMap[Index].Blue - BlueInput[i]))
+            MaxRGBError[2] = ABS(OutputColorMap[Index].Blue - BlueInput[i]);
+    }
+
+#ifdef DEBUG
+    fprintf(stderr,
+            "Quantization L(0) errors: Red = %d, Green = %d, Blue = %d.\n",
+            MaxRGBError[0], MaxRGBError[1], MaxRGBError[2]);
+#endif /* DEBUG */
+
+    free((char *)ColorArrayEntries);
+
+    *ColorMapSize = NewColorMapSize;
+
+    return GIF_OK;
+}
+
+/******************************************************************************
+ Routine to subdivide the RGB space recursively using median cut in each
+ axes alternatingly until ColorMapSize different cubes exists.
+ The biggest cube in one dimension is subdivide unless it has only one entry.
+ Returns GIF_ERROR if failed, otherwise GIF_OK.
+*******************************************************************************/
+static int
+SubdivColorMap(NewColorMapType * NewColorSubdiv,
+               unsigned int ColorMapSize,
+               unsigned int *NewColorMapSize) {
+
+    int MaxSize;
+    unsigned int i, j, Index = 0, NumEntries, MinColor, MaxColor;
+    long Sum, Count;
+    QuantizedColorType *QuantizedColor, **SortArray;
+
+    while (ColorMapSize > *NewColorMapSize) {
+        /* Find candidate for subdivision: */
+        MaxSize = -1;
+        for (i = 0; i < *NewColorMapSize; i++) {
+            for (j = 0; j < 3; j++) {
+                if ((((int)NewColorSubdiv[i].RGBWidth[j]) > MaxSize) &&
+                      (NewColorSubdiv[i].NumEntries > 1)) {
+                    MaxSize = NewColorSubdiv[i].RGBWidth[j];
+                    Index = i;
+                    SortRGBAxis = j;
+                }
+            }
+        }
+
+        if (MaxSize == -1)
+            return GIF_OK;
+
+        /* Split the entry Index into two along the axis SortRGBAxis: */
+
+        /* Sort all elements in that entry along the given axis and split at
+         * the median.  */
+        SortArray = (QuantizedColorType **)malloc(
+                      sizeof(QuantizedColorType *) * 
+                      NewColorSubdiv[Index].NumEntries);
+        if (SortArray == NULL)
+            return GIF_ERROR;
+        for (j = 0, QuantizedColor = NewColorSubdiv[Index].QuantizedColors;
+             j < NewColorSubdiv[Index].NumEntries && QuantizedColor != NULL;
+             j++, QuantizedColor = QuantizedColor->Pnext)
+            SortArray[j] = QuantizedColor;
+
+        qsort(SortArray, NewColorSubdiv[Index].NumEntries,
+              sizeof(QuantizedColorType *), SortCmpRtn);
+
+        /* Relink the sorted list into one: */
+        for (j = 0; j < NewColorSubdiv[Index].NumEntries - 1; j++)
+            SortArray[j]->Pnext = SortArray[j + 1];
+        SortArray[NewColorSubdiv[Index].NumEntries - 1]->Pnext = NULL;
+        NewColorSubdiv[Index].QuantizedColors = QuantizedColor = SortArray[0];
+        free((char *)SortArray);
+
+        /* Now simply add the Counts until we have half of the Count: */
+        Sum = NewColorSubdiv[Index].Count / 2 - QuantizedColor->Count;
+        NumEntries = 1;
+        Count = QuantizedColor->Count;
+        while (QuantizedColor->Pnext != NULL &&
+	       (Sum -= QuantizedColor->Pnext->Count) >= 0 &&
+               QuantizedColor->Pnext->Pnext != NULL) {
+            QuantizedColor = QuantizedColor->Pnext;
+            NumEntries++;
+            Count += QuantizedColor->Count;
+        }
+        /* Save the values of the last color of the first half, and first
+         * of the second half so we can update the Bounding Boxes later.
+         * Also as the colors are quantized and the BBoxes are full 0..255,
+         * they need to be rescaled.
+         */
+        MaxColor = QuantizedColor->RGB[SortRGBAxis]; /* Max. of first half */
+	/* coverity[var_deref_op] */
+        MinColor = QuantizedColor->Pnext->RGB[SortRGBAxis]; /* of second */
+        MaxColor <<= (8 - BITS_PER_PRIM_COLOR);
+        MinColor <<= (8 - BITS_PER_PRIM_COLOR);
+
+        /* Partition right here: */
+        NewColorSubdiv[*NewColorMapSize].QuantizedColors =
+           QuantizedColor->Pnext;
+        QuantizedColor->Pnext = NULL;
+        NewColorSubdiv[*NewColorMapSize].Count = Count;
+        NewColorSubdiv[Index].Count -= Count;
+        NewColorSubdiv[*NewColorMapSize].NumEntries =
+           NewColorSubdiv[Index].NumEntries - NumEntries;
+        NewColorSubdiv[Index].NumEntries = NumEntries;
+        for (j = 0; j < 3; j++) {
+            NewColorSubdiv[*NewColorMapSize].RGBMin[j] =
+               NewColorSubdiv[Index].RGBMin[j];
+            NewColorSubdiv[*NewColorMapSize].RGBWidth[j] =
+               NewColorSubdiv[Index].RGBWidth[j];
+        }
+        NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] =
+           NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] +
+           NewColorSubdiv[*NewColorMapSize].RGBWidth[SortRGBAxis] - MinColor;
+        NewColorSubdiv[*NewColorMapSize].RGBMin[SortRGBAxis] = MinColor;
+
+        NewColorSubdiv[Index].RGBWidth[SortRGBAxis] =
+           MaxColor - NewColorSubdiv[Index].RGBMin[SortRGBAxis];
+
+        (*NewColorMapSize)++;
+    }
+
+    return GIF_OK;
+}
+
+/****************************************************************************
+ Routine called by qsort to compare two entries.
+*****************************************************************************/
+static int
+SortCmpRtn(const void *Entry1,
+           const void *Entry2) {
+
+    return (*((QuantizedColorType **) Entry1))->RGB[SortRGBAxis] -
+       (*((QuantizedColorType **) Entry2))->RGB[SortRGBAxis];
+}
+
+/* end */