331 lines
11 KiB
C
331 lines
11 KiB
C
// Copyright 2011 Google Inc. All Rights Reserved.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Alpha-plane compression.
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#include <assert.h>
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#include <stdlib.h>
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#include "./vp8enci.h"
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#include "../utils/filters.h"
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#include "../utils/quant_levels.h"
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#include "../format_constants.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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// Encodes the given alpha data via specified compression method 'method'.
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// The pre-processing (quantization) is performed if 'quality' is less than 100.
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// For such cases, the encoding is lossy. The valid range is [0, 100] for
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// 'quality' and [0, 1] for 'method':
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// 'method = 0' - No compression;
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// 'method = 1' - Use lossless coder on the alpha plane only
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// 'filter' values [0, 4] correspond to prediction modes none, horizontal,
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// vertical & gradient filters. The prediction mode 4 will try all the
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// prediction modes 0 to 3 and pick the best one.
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// 'effort_level': specifies how much effort must be spent to try and reduce
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// the compressed output size. In range 0 (quick) to 6 (slow).
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//
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// 'output' corresponds to the buffer containing compressed alpha data.
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// This buffer is allocated by this method and caller should call
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// free(*output) when done.
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// 'output_size' corresponds to size of this compressed alpha buffer.
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//
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// Returns 1 on successfully encoding the alpha and
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// 0 if either:
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// invalid quality or method, or
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// memory allocation for the compressed data fails.
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#include "../enc/vp8li.h"
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static int EncodeLossless(const uint8_t* const data, int width, int height,
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int effort_level, // in [0..6] range
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VP8BitWriter* const bw,
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WebPAuxStats* const stats) {
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int ok = 0;
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WebPConfig config;
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WebPPicture picture;
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VP8LBitWriter tmp_bw;
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WebPPictureInit(&picture);
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picture.width = width;
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picture.height = height;
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picture.use_argb = 1;
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picture.stats = stats;
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if (!WebPPictureAlloc(&picture)) return 0;
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// Transfer the alpha values to the green channel.
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{
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int i, j;
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uint32_t* dst = picture.argb;
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const uint8_t* src = data;
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for (j = 0; j < picture.height; ++j) {
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for (i = 0; i < picture.width; ++i) {
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dst[i] = (src[i] << 8) | 0xff000000u;
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}
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src += width;
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dst += picture.argb_stride;
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}
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}
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WebPConfigInit(&config);
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config.lossless = 1;
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config.method = effort_level; // impact is very small
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// Set moderate default quality setting for alpha. Higher qualities (80 and
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// above) could be very slow.
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config.quality = 10.f + 15.f * effort_level;
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if (config.quality > 100.f) config.quality = 100.f;
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ok = VP8LBitWriterInit(&tmp_bw, (width * height) >> 3);
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ok = ok && (VP8LEncodeStream(&config, &picture, &tmp_bw) == VP8_ENC_OK);
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WebPPictureFree(&picture);
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if (ok) {
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const uint8_t* const data = VP8LBitWriterFinish(&tmp_bw);
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const size_t data_size = VP8LBitWriterNumBytes(&tmp_bw);
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VP8BitWriterAppend(bw, data, data_size);
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}
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VP8LBitWriterDestroy(&tmp_bw);
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return ok && !bw->error_;
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}
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// -----------------------------------------------------------------------------
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static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,
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int method, int filter, int reduce_levels,
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int effort_level, // in [0..6] range
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uint8_t* const tmp_alpha,
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VP8BitWriter* const bw,
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WebPAuxStats* const stats) {
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int ok = 0;
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const uint8_t* alpha_src;
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WebPFilterFunc filter_func;
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uint8_t header;
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size_t expected_size;
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const size_t data_size = width * height;
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assert((uint64_t)data_size == (uint64_t)width * height); // as per spec
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assert(filter >= 0 && filter < WEBP_FILTER_LAST);
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assert(method >= ALPHA_NO_COMPRESSION);
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assert(method <= ALPHA_LOSSLESS_COMPRESSION);
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assert(sizeof(header) == ALPHA_HEADER_LEN);
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// TODO(skal): have a common function and #define's to validate alpha params.
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expected_size =
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(method == ALPHA_NO_COMPRESSION) ? (ALPHA_HEADER_LEN + data_size)
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: (data_size >> 5);
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header = method | (filter << 2);
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if (reduce_levels) header |= ALPHA_PREPROCESSED_LEVELS << 4;
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VP8BitWriterInit(bw, expected_size);
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VP8BitWriterAppend(bw, &header, ALPHA_HEADER_LEN);
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filter_func = WebPFilters[filter];
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if (filter_func) {
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filter_func(data, width, height, 1, width, tmp_alpha);
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alpha_src = tmp_alpha;
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} else {
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alpha_src = data;
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}
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if (method == ALPHA_NO_COMPRESSION) {
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ok = VP8BitWriterAppend(bw, alpha_src, width * height);
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ok = ok && !bw->error_;
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} else {
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ok = EncodeLossless(alpha_src, width, height, effort_level, bw, stats);
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VP8BitWriterFinish(bw);
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}
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return ok;
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}
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// -----------------------------------------------------------------------------
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// TODO(skal): move to dsp/ ?
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static void CopyPlane(const uint8_t* src, int src_stride,
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uint8_t* dst, int dst_stride, int width, int height) {
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while (height-- > 0) {
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memcpy(dst, src, width);
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src += src_stride;
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dst += dst_stride;
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}
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}
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static int EncodeAlpha(VP8Encoder* const enc,
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int quality, int method, int filter,
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int effort_level,
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uint8_t** const output, size_t* const output_size) {
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const WebPPicture* const pic = enc->pic_;
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const int width = pic->width;
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const int height = pic->height;
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uint8_t* quant_alpha = NULL;
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const size_t data_size = width * height;
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uint64_t sse = 0;
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int ok = 1;
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const int reduce_levels = (quality < 100);
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// quick sanity checks
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assert((uint64_t)data_size == (uint64_t)width * height); // as per spec
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assert(enc != NULL && pic != NULL && pic->a != NULL);
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assert(output != NULL && output_size != NULL);
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assert(width > 0 && height > 0);
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assert(pic->a_stride >= width);
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assert(filter >= WEBP_FILTER_NONE && filter <= WEBP_FILTER_FAST);
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if (quality < 0 || quality > 100) {
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return 0;
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}
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if (method < ALPHA_NO_COMPRESSION || method > ALPHA_LOSSLESS_COMPRESSION) {
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return 0;
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}
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quant_alpha = (uint8_t*)malloc(data_size);
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if (quant_alpha == NULL) {
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return 0;
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}
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// Extract alpha data (width x height) from raw_data (stride x height).
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CopyPlane(pic->a, pic->a_stride, quant_alpha, width, width, height);
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if (reduce_levels) { // No Quantization required for 'quality = 100'.
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// 16 alpha levels gives quite a low MSE w.r.t original alpha plane hence
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// mapped to moderate quality 70. Hence Quality:[0, 70] -> Levels:[2, 16]
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// and Quality:]70, 100] -> Levels:]16, 256].
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const int alpha_levels = (quality <= 70) ? (2 + quality / 5)
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: (16 + (quality - 70) * 8);
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ok = QuantizeLevels(quant_alpha, width, height, alpha_levels, &sse);
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}
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if (ok) {
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VP8BitWriter bw;
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int test_filter;
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uint8_t* filtered_alpha = NULL;
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// We always test WEBP_FILTER_NONE first.
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ok = EncodeAlphaInternal(quant_alpha, width, height,
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method, WEBP_FILTER_NONE, reduce_levels,
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effort_level, NULL, &bw, pic->stats);
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if (!ok) {
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VP8BitWriterWipeOut(&bw);
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goto End;
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}
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if (filter == WEBP_FILTER_FAST) { // Quick estimate of a second candidate?
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filter = EstimateBestFilter(quant_alpha, width, height, width);
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}
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// Stop?
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if (filter == WEBP_FILTER_NONE) {
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goto Ok;
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}
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filtered_alpha = (uint8_t*)malloc(data_size);
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ok = (filtered_alpha != NULL);
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if (!ok) {
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goto End;
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}
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// Try the other mode(s).
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{
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WebPAuxStats best_stats;
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size_t best_score = VP8BitWriterSize(&bw);
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memset(&best_stats, 0, sizeof(best_stats)); // prevent spurious warning
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if (pic->stats != NULL) best_stats = *pic->stats;
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for (test_filter = WEBP_FILTER_HORIZONTAL;
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ok && (test_filter <= WEBP_FILTER_GRADIENT);
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++test_filter) {
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VP8BitWriter tmp_bw;
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if (filter != WEBP_FILTER_BEST && test_filter != filter) {
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continue;
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}
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ok = EncodeAlphaInternal(quant_alpha, width, height,
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method, test_filter, reduce_levels,
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effort_level, filtered_alpha, &tmp_bw,
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pic->stats);
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if (ok) {
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const size_t score = VP8BitWriterSize(&tmp_bw);
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if (score < best_score) {
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// swap bitwriter objects.
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VP8BitWriter tmp = tmp_bw;
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tmp_bw = bw;
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bw = tmp;
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best_score = score;
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if (pic->stats != NULL) best_stats = *pic->stats;
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}
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} else {
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VP8BitWriterWipeOut(&bw);
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}
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VP8BitWriterWipeOut(&tmp_bw);
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}
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if (pic->stats != NULL) *pic->stats = best_stats;
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}
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Ok:
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if (ok) {
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*output_size = VP8BitWriterSize(&bw);
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*output = VP8BitWriterBuf(&bw);
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if (pic->stats != NULL) { // need stats?
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pic->stats->coded_size += (int)(*output_size);
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enc->sse_[3] = sse;
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}
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}
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free(filtered_alpha);
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}
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End:
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free(quant_alpha);
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return ok;
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}
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//------------------------------------------------------------------------------
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// Main calls
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void VP8EncInitAlpha(VP8Encoder* const enc) {
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enc->has_alpha_ = WebPPictureHasTransparency(enc->pic_);
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enc->alpha_data_ = NULL;
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enc->alpha_data_size_ = 0;
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}
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int VP8EncFinishAlpha(VP8Encoder* const enc) {
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if (enc->has_alpha_) {
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const WebPConfig* config = enc->config_;
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uint8_t* tmp_data = NULL;
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size_t tmp_size = 0;
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const int effort_level = config->method; // maps to [0..6]
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const WEBP_FILTER_TYPE filter =
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(config->alpha_filtering == 0) ? WEBP_FILTER_NONE :
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(config->alpha_filtering == 1) ? WEBP_FILTER_FAST :
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WEBP_FILTER_BEST;
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if (!EncodeAlpha(enc, config->alpha_quality, config->alpha_compression,
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filter, effort_level, &tmp_data, &tmp_size)) {
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return 0;
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}
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if (tmp_size != (uint32_t)tmp_size) { // Sanity check.
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free(tmp_data);
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return 0;
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}
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enc->alpha_data_size_ = (uint32_t)tmp_size;
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enc->alpha_data_ = tmp_data;
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}
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return WebPReportProgress(enc->pic_, enc->percent_ + 20, &enc->percent_);
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}
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void VP8EncDeleteAlpha(VP8Encoder* const enc) {
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free(enc->alpha_data_);
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enc->alpha_data_ = NULL;
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enc->alpha_data_size_ = 0;
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enc->has_alpha_ = 0;
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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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