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Diffstat (limited to 'gcc-4.4.3/libjava/classpath/gnu/javax/imageio/png/PNGFilter.java')
| -rw-r--r-- | gcc-4.4.3/libjava/classpath/gnu/javax/imageio/png/PNGFilter.java | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/gcc-4.4.3/libjava/classpath/gnu/javax/imageio/png/PNGFilter.java b/gcc-4.4.3/libjava/classpath/gnu/javax/imageio/png/PNGFilter.java new file mode 100644 index 000000000..63af19929 --- /dev/null +++ b/gcc-4.4.3/libjava/classpath/gnu/javax/imageio/png/PNGFilter.java @@ -0,0 +1,237 @@ +/* PNGFilter.java -- PNG image filters. + Copyright (C) 2006 Free Software Foundation + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package gnu.javax.imageio.png; + +/** + * A utility class of static methods implementing the PNG filtering algorithms. + */ +public class PNGFilter +{ + + public static final byte FILTER_NONE = 0; + public static final byte FILTER_SUB = 1; + public static final byte FILTER_UP = 2; + public static final byte FILTER_AVERAGE = 3; + public static final byte FILTER_PAETH = 4; + + /** + * Return whether a filter should be used or FILTER_NONE, + * following the recommendations in the PNG spec. + */ + public static boolean useFilter( PNGHeader header ) + { + switch( header.getColorType() ) + { + case PNGHeader.INDEXED: + return false; + + case PNGHeader.GRAYSCALE: + case PNGHeader.RGB: + if( header.bytesPerPixel() <= 1 ) + return false; + case PNGHeader.GRAYSCALE_WITH_ALPHA: + case PNGHeader.RGB_WITH_ALPHA: + default: + return true; + } + } + + /** + * Heuristic for adaptively choosing a filter, following the scheme + * suggested in the PNG spec. + * @return a fiter type. + */ + public static byte chooseFilter( byte[] scanline, byte[] lastScanline, + int bpp) + + { + long[] values = new long[5]; + int idx = 0; + for( int i = 0; i < 5; i++ ) + { + byte[] filtered = filterScanline((byte)i, scanline, lastScanline, bpp); + values[i] = 0; + for(int j = 0; j < filtered.length; j++ ) + values[i] += (int)(filtered[j] & 0xFF); + if( values[ idx ] > values[i] ) + idx = i; + } + return (byte)idx; + } + + /** + * Filter a scanline. + */ + public static byte[] filterScanline( byte filtertype, byte[] scanline, + byte[] lastScanline, int bpp) + { + int stride = scanline.length; + byte[] out = new byte[ stride ]; + switch( filtertype ) + { + case FILTER_SUB: + for( int i = 0; i < bpp; i++) + out[ i ] = scanline[ i ]; + + for( int i = bpp; i < stride; i++ ) + out[i] = (byte)(scanline[ i ] - + scanline[ i - bpp ]); + break; + + case FILTER_UP: + for( int i = 0; i < stride; i++ ) + out[ i ] = (byte)(scanline[ i ] - lastScanline[ i ]); + break; + + case FILTER_AVERAGE: + for( int i = 0; i < bpp; i++) + out[ i ] = (byte)((scanline[ i ] & 0xFF) - ((lastScanline[ i ] & 0xFF) >> 1)); + for( int i = bpp; i < stride; i++ ) + out[ i ] = (byte)((scanline[ i ] & 0xFF) - + (((scanline[ i - bpp ] & 0xFF) + + (lastScanline[ i ] & 0xFF)) >> 1)); + break; + + case FILTER_PAETH: + for( int i = 0; i < stride; i++ ) + { + int x; + { + int a, b, c; + if( i >= bpp ) + { + a = (scanline[ i - bpp ] & 0xFF); // left + c = (lastScanline[ i - bpp ] & 0xFF); // upper-left + } + else + a = c = 0; + b = (lastScanline[ i ] & 0xFF); // up + + int p = (a + b - c); // initial estimate + // distances to a, b, c + int pa = (p > a) ? p - a : a - p; + int pb = (p > b) ? p - b : b - p; + int pc = (p > c) ? p - c : c - p; + // return nearest of a,b,c, + // breaking ties in order a,b,c. + if( pa <= pb && pa <= pc ) x = a; + else { if( pb <= pc ) x = b; + else x = c; + } + } + out[ i ] = (byte)(scanline[ i ] - x); + } + break; + default: + case FILTER_NONE: + return scanline; + } + return out; + } + + /** + * Unfilter a scanline. + */ + public static byte[] unFilterScanline( int filtertype, byte[] scanline, + byte[] lastScanline, int bpp) + { + int stride = scanline.length; + byte[] out = new byte[ stride ]; + switch( filtertype ) + { + + case FILTER_NONE: + System.arraycopy( scanline, 0, out, 0, stride ); + break; + + case FILTER_SUB: + for( int i = 0; i < bpp; i++) + out[ i ] = scanline[ i ]; + + for( int i = bpp; i < stride; i++ ) + out[ i ] = (byte)(scanline[ i ] + + out[ i - bpp ]); + break; + + case FILTER_UP: + for( int i = 0; i < stride; i++ ) + out[ i ] = (byte)(scanline[ i ] + lastScanline[ i ]); + break; + + case FILTER_AVERAGE: + for( int i = 0; i < bpp; i++) + out[ i ] = (byte)((scanline[ i ] & 0xFF) + ((lastScanline[ i ] & 0xFF) >> 1)); + for( int i = bpp; i < stride; i++ ) + out[ i ] = (byte)((scanline[ i ] & 0xFF) + + (((out[ i - bpp ] & 0xFF) + (lastScanline[ i ] & 0xFF)) >> 1)); + break; + + case FILTER_PAETH: + for( int i = 0; i < stride; i++ ) + { + int x; + { + int a, b, c; + if( i >= bpp ) + { + a = (out[ i - bpp ] & 0xFF); // left + c = (lastScanline[ i - bpp ] & 0xFF); // upper-left + } + else + a = c = 0; + b = (lastScanline[ i ] & 0xFF); // up + + int p = (a + b - c); // initial estimate + // distances to a, b, c + int pa = (p > a) ? p - a : a - p; + int pb = (p > b) ? p - b : b - p; + int pc = (p > c) ? p - c : c - p; + // return nearest of a,b,c, + // breaking ties in order a,b,c. + if( pa <= pb && pa <= pc ) x = a; + else { if( pb <= pc ) x = b; + else x = c; + } + } + out[ i ] = (byte)(scanline[ i ] + x); + } + break; + } + return out; + } +}
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