diff --git a/jni/GifTranscoder.h b/jni/GifTranscoder.h
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+++ b/jni/GifTranscoder.h
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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