426 lines
14 KiB
C
426 lines
14 KiB
C
// Copyright 2011 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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// 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 "../dsp/dsp.h"
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#include "../utils/filters.h"
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#include "../utils/quant_levels.h"
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#include "../utils/utils.h"
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#include "webp/format_constants.h"
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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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// WebPSafeFree(*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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VP8LBitWriter* 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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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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WebPDispatchAlphaToGreen(data, width, picture.width, picture.height,
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picture.argb, picture.argb_stride);
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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 a low default quality for encoding alpha. Ensure that Alpha quality at
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// lower methods (3 and below) is less than the threshold for triggering
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// costly 'BackwardReferencesTraceBackwards'.
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config.quality = 8.f * effort_level;
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assert(config.quality >= 0 && config.quality <= 100.f);
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ok = (VP8LEncodeStream(&config, &picture, bw) == VP8_ENC_OK);
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WebPPictureFree(&picture);
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ok = ok && !bw->error_;
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if (!ok) {
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VP8LBitWriterWipeOut(bw);
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return 0;
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}
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return 1;
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}
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// -----------------------------------------------------------------------------
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// Small struct to hold the result of a filter mode compression attempt.
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typedef struct {
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size_t score;
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VP8BitWriter bw;
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WebPAuxStats stats;
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} FilterTrial;
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// This function always returns an initialized 'bw' object, even upon error.
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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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FilterTrial* result) {
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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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const size_t data_size = width * height;
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const uint8_t* output = NULL;
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size_t output_size = 0;
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VP8LBitWriter tmp_bw;
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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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filter_func = WebPFilters[filter];
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if (filter_func != NULL) {
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filter_func(data, width, height, 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 = VP8LBitWriterInit(&tmp_bw, data_size >> 3);
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ok = ok && EncodeLossless(alpha_src, width, height, effort_level,
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&tmp_bw, &result->stats);
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if (ok) {
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output = VP8LBitWriterFinish(&tmp_bw);
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output_size = VP8LBitWriterNumBytes(&tmp_bw);
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if (output_size > data_size) {
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// compressed size is larger than source! Revert to uncompressed mode.
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method = ALPHA_NO_COMPRESSION;
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VP8LBitWriterWipeOut(&tmp_bw);
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}
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} else {
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VP8LBitWriterWipeOut(&tmp_bw);
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return 0;
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}
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}
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if (method == ALPHA_NO_COMPRESSION) {
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output = alpha_src;
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output_size = data_size;
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ok = 1;
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}
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// Emit final result.
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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(&result->bw, ALPHA_HEADER_LEN + output_size);
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ok = ok && VP8BitWriterAppend(&result->bw, &header, ALPHA_HEADER_LEN);
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ok = ok && VP8BitWriterAppend(&result->bw, output, output_size);
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if (method != ALPHA_NO_COMPRESSION) {
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VP8LBitWriterWipeOut(&tmp_bw);
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}
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ok = ok && !result->bw.error_;
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result->score = VP8BitWriterSize(&result->bw);
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return ok;
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}
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// -----------------------------------------------------------------------------
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static int GetNumColors(const uint8_t* data, int width, int height,
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int stride) {
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int j;
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int colors = 0;
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uint8_t color[256] = { 0 };
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for (j = 0; j < height; ++j) {
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int i;
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const uint8_t* const p = data + j * stride;
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for (i = 0; i < width; ++i) {
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color[p[i]] = 1;
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}
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}
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for (j = 0; j < 256; ++j) {
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if (color[j] > 0) ++colors;
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}
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return colors;
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}
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#define FILTER_TRY_NONE (1 << WEBP_FILTER_NONE)
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#define FILTER_TRY_ALL ((1 << WEBP_FILTER_LAST) - 1)
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// Given the input 'filter' option, return an OR'd bit-set of filters to try.
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static uint32_t GetFilterMap(const uint8_t* alpha, int width, int height,
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int filter, int effort_level) {
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uint32_t bit_map = 0U;
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if (filter == WEBP_FILTER_FAST) {
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// Quick estimate of the best candidate.
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int try_filter_none = (effort_level > 3);
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const int kMinColorsForFilterNone = 16;
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const int kMaxColorsForFilterNone = 192;
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const int num_colors = GetNumColors(alpha, width, height, width);
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// For low number of colors, NONE yields better compression.
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filter = (num_colors <= kMinColorsForFilterNone)
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? WEBP_FILTER_NONE
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: WebPEstimateBestFilter(alpha, width, height, width);
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bit_map |= 1 << filter;
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// For large number of colors, try FILTER_NONE in addition to the best
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// filter as well.
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if (try_filter_none || num_colors > kMaxColorsForFilterNone) {
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bit_map |= FILTER_TRY_NONE;
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}
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} else if (filter == WEBP_FILTER_NONE) {
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bit_map = FILTER_TRY_NONE;
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} else { // WEBP_FILTER_BEST -> try all
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bit_map = FILTER_TRY_ALL;
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}
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return bit_map;
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}
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static void InitFilterTrial(FilterTrial* const score) {
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score->score = (size_t)~0U;
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VP8BitWriterInit(&score->bw, 0);
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}
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static int ApplyFiltersAndEncode(const uint8_t* alpha, int width, int height,
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size_t data_size, int method, int filter,
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int reduce_levels, int effort_level,
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uint8_t** const output,
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size_t* const output_size,
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WebPAuxStats* const stats) {
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int ok = 1;
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FilterTrial best;
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uint32_t try_map =
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GetFilterMap(alpha, width, height, filter, effort_level);
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InitFilterTrial(&best);
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if (try_map != FILTER_TRY_NONE) {
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uint8_t* filtered_alpha = (uint8_t*)WebPSafeMalloc(1ULL, data_size);
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if (filtered_alpha == NULL) return 0;
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for (filter = WEBP_FILTER_NONE; ok && try_map; ++filter, try_map >>= 1) {
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if (try_map & 1) {
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FilterTrial trial;
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ok = EncodeAlphaInternal(alpha, width, height, method, filter,
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reduce_levels, effort_level, filtered_alpha,
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&trial);
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if (ok && trial.score < best.score) {
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VP8BitWriterWipeOut(&best.bw);
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best = trial;
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} else {
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VP8BitWriterWipeOut(&trial.bw);
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}
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}
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}
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WebPSafeFree(filtered_alpha);
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} else {
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ok = EncodeAlphaInternal(alpha, width, height, method, WEBP_FILTER_NONE,
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reduce_levels, effort_level, NULL, &best);
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}
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if (ok) {
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if (stats != NULL) {
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stats->lossless_features = best.stats.lossless_features;
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stats->histogram_bits = best.stats.histogram_bits;
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stats->transform_bits = best.stats.transform_bits;
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stats->cache_bits = best.stats.cache_bits;
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stats->palette_size = best.stats.palette_size;
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stats->lossless_size = best.stats.lossless_size;
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stats->lossless_hdr_size = best.stats.lossless_hdr_size;
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stats->lossless_data_size = best.stats.lossless_data_size;
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}
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*output_size = VP8BitWriterSize(&best.bw);
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*output = VP8BitWriterBuf(&best.bw);
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} else {
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VP8BitWriterWipeOut(&best.bw);
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}
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return ok;
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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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if (method == ALPHA_NO_COMPRESSION) {
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// Don't filter, as filtering will make no impact on compressed size.
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filter = WEBP_FILTER_NONE;
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}
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quant_alpha = (uint8_t*)WebPSafeMalloc(1ULL, 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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WebPCopyPlane(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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VP8FiltersInit();
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ok = ApplyFiltersAndEncode(quant_alpha, width, height, data_size, method,
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filter, reduce_levels, effort_level, output,
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output_size, pic->stats);
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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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WebPSafeFree(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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static int CompressAlphaJob(VP8Encoder* const enc, void* dummy) {
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const WebPConfig* config = enc->config_;
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uint8_t* alpha_data = NULL;
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size_t alpha_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, &alpha_data, &alpha_size)) {
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return 0;
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}
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if (alpha_size != (uint32_t)alpha_size) { // Sanity check.
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WebPSafeFree(alpha_data);
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return 0;
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}
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enc->alpha_data_size_ = (uint32_t)alpha_size;
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enc->alpha_data_ = alpha_data;
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(void)dummy;
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return 1;
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}
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void VP8EncInitAlpha(VP8Encoder* const enc) {
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WebPInitAlphaProcessing();
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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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if (enc->thread_level_ > 0) {
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WebPWorker* const worker = &enc->alpha_worker_;
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WebPGetWorkerInterface()->Init(worker);
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worker->data1 = enc;
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worker->data2 = NULL;
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worker->hook = (WebPWorkerHook)CompressAlphaJob;
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}
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}
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int VP8EncStartAlpha(VP8Encoder* const enc) {
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if (enc->has_alpha_) {
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if (enc->thread_level_ > 0) {
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WebPWorker* const worker = &enc->alpha_worker_;
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// Makes sure worker is good to go.
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if (!WebPGetWorkerInterface()->Reset(worker)) {
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return 0;
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}
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WebPGetWorkerInterface()->Launch(worker);
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return 1;
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} else {
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return CompressAlphaJob(enc, NULL); // just do the job right away
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}
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}
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return 1;
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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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if (enc->thread_level_ > 0) {
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WebPWorker* const worker = &enc->alpha_worker_;
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if (!WebPGetWorkerInterface()->Sync(worker)) return 0; // error
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}
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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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int VP8EncDeleteAlpha(VP8Encoder* const enc) {
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int ok = 1;
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if (enc->thread_level_ > 0) {
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WebPWorker* const worker = &enc->alpha_worker_;
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// finish anything left in flight
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ok = WebPGetWorkerInterface()->Sync(worker);
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// still need to end the worker, even if !ok
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WebPGetWorkerInterface()->End(worker);
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}
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WebPSafeFree(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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return ok;
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}
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