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https://github.com/webmproject/libwebp.git
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606c4304c4
We reduce transparency by turning some transparent pixels into corresponding RGB values from previous canvas. This improves compression by about 23%. Change-Id: I02d70a43a1d0906ac09a7e2dc510be3b2d38f593
116 lines
4.7 KiB
C
116 lines
4.7 KiB
C
// Copyright 2013 Google Inc. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the COPYING file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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// -----------------------------------------------------------------------------
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//
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// Helper structs and methods for gif2webp tool.
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//
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// Author: Urvang (urvang@google.com)
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#ifndef WEBP_EXAMPLES_GIF2WEBP_UTIL_H_
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#define WEBP_EXAMPLES_GIF2WEBP_UTIL_H_
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#include <stdlib.h>
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#include "webp/mux.h"
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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//------------------------------------------------------------------------------
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// Frame cache.
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typedef struct WebPFrameCache WebPFrameCache;
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// Given the minimum distance between key frames 'kmin' and maximum distance
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// between key frames 'kmax', returns an appropriately allocated cache object.
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// Use WebPFrameCacheDelete() to deallocate the 'cache'.
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WebPFrameCache* WebPFrameCacheNew(size_t kmin, size_t kmax);
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// Release all the frame data from 'cache' and free 'cache'.
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void WebPFrameCacheDelete(WebPFrameCache* const cache);
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// Add encoded frame in the cache. 'sub_frame_info' and 'sub_frame_pic' are used
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// to encode the frame rectangle, while 'key_frame_info' and 'key_frame_pic' are
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// used to encode the key frame. Either 'sub_frame_pic' (and 'sub_frame_info')
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// or 'key_frame_pic' (and 'key_frame_info') can be NULL; in which case the
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// corresponding variant will be omitted.
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// Returns true on success.
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int WebPFrameCacheAddFrame(WebPFrameCache* const cache,
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const WebPConfig* const config,
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const WebPMuxFrameInfo* const sub_frame_info,
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WebPPicture* const sub_frame_pic,
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const WebPMuxFrameInfo* const key_frame_info,
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WebPPicture* const key_frame_pic);
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// Flush the *ready* frames from cache and add them to 'mux'. If 'verbose' is
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// true, prints the information about these frames.
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WebPMuxError WebPFrameCacheFlush(WebPFrameCache* const cache, int verbose,
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WebPMux* const mux);
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// Similar to 'WebPFrameCacheFlushFrames()', but flushes *all* the frames.
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WebPMuxError WebPFrameCacheFlushAll(WebPFrameCache* const cache, int verbose,
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WebPMux* const mux);
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// Returns true if subsequent call to WebPFrameCacheAddFrame() should
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// incorporate a potential keyframe.
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int WebPFrameCacheShouldTryKeyFrame(const WebPFrameCache* const cache);
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//------------------------------------------------------------------------------
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// Frame rectangle and related utilities.
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#define TRANSPARENT_COLOR 0x00ffffff
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typedef struct {
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int x_offset, y_offset, width, height;
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} WebPFrameRect;
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struct WebPPicture;
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// Clear pixels in 'picture' within given 'rect' to transparent color.
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void WebPUtilClearPic(struct WebPPicture* const picture,
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const WebPFrameRect* const rect);
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// Copy pixels from 'src' to 'dst' honoring strides. 'src' and 'dst' are assumed
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// to be already allocated.
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void WebPUtilCopyPixels(const struct WebPPicture* const src,
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WebPPicture* const dst);
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// Given 'src' picture and its frame rectangle 'rect', blend it into 'dst'.
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void WebPUtilBlendPixels(const struct WebPPicture* const src,
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const WebPFrameRect* const src_rect,
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struct WebPPicture* const dst);
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// Replace transparent pixels within 'dst_rect' of 'dst' by those in the 'src'.
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void WebPUtilReduceTransparency(const struct WebPPicture* const src,
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const WebPFrameRect* const dst_rect,
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struct WebPPicture* const dst);
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//------------------------------------------------------------------------------
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// Key frame related.
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// Returns true if 'curr' frame with frame rectangle 'curr_rect' is a key frame,
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// that is, it can be decoded independently of 'prev' canvas.
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int WebPUtilIsKeyFrame(const WebPPicture* const curr,
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const WebPFrameRect* const curr_rect,
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const WebPPicture* const prev);
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// Given 'prev' frame and current frame rectangle 'rect', convert 'curr' frame
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// to a key frame.
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void WebPUtilConvertToKeyFrame(const WebPPicture* const prev,
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WebPFrameRect* const rect,
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WebPPicture* const curr);
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//------------------------------------------------------------------------------
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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#endif // WEBP_EXAMPLES_GIF2WEBP_UTIL_H_
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