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