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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef GIF_TRANSCODER_H
#define GIF_TRANSCODER_H
#include <sys/types.h>
#include "gif_lib.h"
// 24-bit color with alpha, stored in order: A, R, G, B.
// The internal GIF render buffer stores pixels using this format.
typedef uint32_t ColorARGB;
// Compresses a GIF (probably animated) so it can be sent via MMS, which generally has a 1 MB limit
// on attachments. GIF image data is already compressed (LZW), so to achieve further reduction in
// file size, we reduce the image dimensions.
//
// Helpful GIF references:
// GIF89A spec: http://www.w3.org/Graphics/GIF/spec-gif89a.txt
// What's in a GIF: http://giflib.sourceforge.net/whatsinagif/index.html
//
class GifTranscoder {
public:
GifTranscoder() {}
~GifTranscoder() {}
// Resizes a GIF's width and height to 50% of their original dimensions. The new file is
// written to pathOut.
//
// The image is resized using a box filter, which averages the colors in each 2x2 box of pixels
// in the source to generate the color of the pixel in the destination.
//
// Returns GIF_OK (1) on success, or GIF_ERROR (0) on failure.
int transcode(const char* pathIn, const char* pathOut);
private:
// Implementation of the box filter algorithm.
static bool resizeBoxFilter(GifFileType* gifIn, GifFileType* gifOut);
// Reads the raster data for the current image of the GIF.
static bool readImage(GifFileType* gifIn, GifByteType* rasterBits);
// Renders the current image of the GIF into the supplied render buffer.
static bool renderImage(GifFileType* gifIn,
GifByteType* rasterBits,
int imageIndex,
int transparentColorIndex,
ColorARGB* renderBuffer,
ColorARGB bgColor,
GifImageDesc prevImageDimens,
int prevImageDisposalMode);
// Fills a rectangle in the buffer with a solid color.
static void fillRect(ColorARGB* renderBuffer,
int imageWidth,
int imageHeight,
int left,
int top,
int width,
int height,
ColorARGB color);
// Computes the color for the pixel (x,y) in the current image in the output GIF.
static GifByteType computeNewColorIndex(GifFileType* gifIn,
int transparentColorIndex,
ColorARGB* renderBuffer,
int x,
int y);
// Computes the average color (by averaging the per-channel (ARGB) values).
static ColorARGB computeAverage(ColorARGB c1, ColorARGB c2, ColorARGB c3, ColorARGB c4);
// Searches a color map for the color closest (Euclidean distance) to the target color.
static GifByteType findBestColor(ColorMapObject* colorMap, int transparentColorIndex,
ColorARGB targetColor);
// Computes distance (squared) between 2 colors, considering each channel a separate dimension.
static int computeDistance(ColorARGB c1, ColorARGB c2);
// Returns the local color map of the current image (if any), or else the global color map.
static ColorMapObject* getColorMap(GifFileType* gifIn);
// Returns an indexed color from the color map.
static ColorARGB getColorARGB(ColorMapObject* colorMap, int transparentColorIndex,
GifByteType colorIndex);
// Converts a 24-bit GIF color (RGB) to a 32-bit ARGB color.
static ColorARGB gifColorToColorARGB(const GifColorType& color);
};
// Wrapper class that automatically closes the GIF files when the wrapper goes out of scope.
class GifFilesCloser {
public:
GifFilesCloser() {}
~GifFilesCloser();
void setGifIn(GifFileType* gifIn);
void releaseGifIn();
void setGifOut(GifFileType* gifOut);
void releaseGifOut();
private:
GifFileType* mGifIn = NULL;
GifFileType* mGifOut = NULL;
};
#endif // GIF_TRANSCODER_H
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