455 lines
16 KiB
C
455 lines
16 KiB
C
// Copyright 2015 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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// AnimDecoder implementation.
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//
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#ifdef HAVE_CONFIG_H
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#include "../webp/config.h"
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#endif
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#include <assert.h>
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#include <string.h>
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#include "../utils/utils.h"
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#include "../webp/decode.h"
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#include "../webp/demux.h"
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#define NUM_CHANNELS 4
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typedef void (*BlendRowFunc)(uint32_t* const, const uint32_t* const, int);
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static void BlendPixelRowNonPremult(uint32_t* const src,
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const uint32_t* const dst, int num_pixels);
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static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst,
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int num_pixels);
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struct WebPAnimDecoder {
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WebPDemuxer* demux_; // Demuxer created from given WebP bitstream.
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WebPDecoderConfig config_; // Decoder config.
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// Note: we use a pointer to a function blending multiple pixels at a time to
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// allow possible inlining of per-pixel blending function.
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BlendRowFunc blend_func_; // Pointer to the chose blend row function.
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WebPAnimInfo info_; // Global info about the animation.
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uint8_t* curr_frame_; // Current canvas (not disposed).
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uint8_t* prev_frame_disposed_; // Previous canvas (properly disposed).
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int prev_frame_timestamp_; // Previous frame timestamp (milliseconds).
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WebPIterator prev_iter_; // Iterator object for previous frame.
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int prev_frame_was_keyframe_; // True if previous frame was a keyframe.
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int next_frame_; // Index of the next frame to be decoded
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// (starting from 1).
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};
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static void DefaultDecoderOptions(WebPAnimDecoderOptions* const dec_options) {
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dec_options->color_mode = MODE_RGBA;
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dec_options->use_threads = 0;
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}
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int WebPAnimDecoderOptionsInitInternal(WebPAnimDecoderOptions* dec_options,
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int abi_version) {
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if (dec_options == NULL ||
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WEBP_ABI_IS_INCOMPATIBLE(abi_version, WEBP_DEMUX_ABI_VERSION)) {
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return 0;
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}
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DefaultDecoderOptions(dec_options);
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return 1;
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}
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static int ApplyDecoderOptions(const WebPAnimDecoderOptions* const dec_options,
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WebPAnimDecoder* const dec) {
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WEBP_CSP_MODE mode;
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WebPDecoderConfig* config = &dec->config_;
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assert(dec_options != NULL);
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mode = dec_options->color_mode;
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if (mode != MODE_RGBA && mode != MODE_BGRA &&
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mode != MODE_rgbA && mode != MODE_bgrA) {
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return 0;
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}
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dec->blend_func_ = (mode == MODE_RGBA || mode == MODE_BGRA)
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? &BlendPixelRowNonPremult
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: &BlendPixelRowPremult;
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WebPInitDecoderConfig(config);
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config->output.colorspace = mode;
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config->output.is_external_memory = 1;
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config->options.use_threads = dec_options->use_threads;
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// Note: config->output.u.RGBA is set at the time of decoding each frame.
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return 1;
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}
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WebPAnimDecoder* WebPAnimDecoderNewInternal(
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const WebPData* webp_data, const WebPAnimDecoderOptions* dec_options,
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int abi_version) {
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WebPAnimDecoderOptions options;
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WebPAnimDecoder* dec = NULL;
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if (webp_data == NULL ||
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WEBP_ABI_IS_INCOMPATIBLE(abi_version, WEBP_DEMUX_ABI_VERSION)) {
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return NULL;
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}
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// Note: calloc() so that the pointer members are initialized to NULL.
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dec = (WebPAnimDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec));
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if (dec == NULL) goto Error;
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if (dec_options != NULL) {
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options = *dec_options;
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} else {
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DefaultDecoderOptions(&options);
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}
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if (!ApplyDecoderOptions(&options, dec)) goto Error;
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dec->demux_ = WebPDemux(webp_data);
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if (dec->demux_ == NULL) goto Error;
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dec->info_.canvas_width = WebPDemuxGetI(dec->demux_, WEBP_FF_CANVAS_WIDTH);
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dec->info_.canvas_height = WebPDemuxGetI(dec->demux_, WEBP_FF_CANVAS_HEIGHT);
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dec->info_.loop_count = WebPDemuxGetI(dec->demux_, WEBP_FF_LOOP_COUNT);
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dec->info_.bgcolor = WebPDemuxGetI(dec->demux_, WEBP_FF_BACKGROUND_COLOR);
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dec->info_.frame_count = WebPDemuxGetI(dec->demux_, WEBP_FF_FRAME_COUNT);
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// Note: calloc() because we fill frame with zeroes as well.
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dec->curr_frame_ = (uint8_t*)WebPSafeCalloc(
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dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height);
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if (dec->curr_frame_ == NULL) goto Error;
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dec->prev_frame_disposed_ = (uint8_t*)WebPSafeCalloc(
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dec->info_.canvas_width * NUM_CHANNELS, dec->info_.canvas_height);
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if (dec->prev_frame_disposed_ == NULL) goto Error;
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WebPAnimDecoderReset(dec);
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return dec;
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Error:
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WebPAnimDecoderDelete(dec);
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return NULL;
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}
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int WebPAnimDecoderGetInfo(const WebPAnimDecoder* dec, WebPAnimInfo* info) {
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if (dec == NULL || info == NULL) return 0;
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*info = dec->info_;
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return 1;
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}
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// Returns true if the frame covers the full canvas.
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static int IsFullFrame(int width, int height, int canvas_width,
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int canvas_height) {
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return (width == canvas_width && height == canvas_height);
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}
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// Clear the canvas to transparent.
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static int ZeroFillCanvas(uint8_t* buf, uint32_t canvas_width,
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uint32_t canvas_height) {
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const uint64_t size =
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(uint64_t)canvas_width * canvas_height * NUM_CHANNELS * sizeof(*buf);
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if (size != (size_t)size) return 0;
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memset(buf, 0, (size_t)size);
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return 1;
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}
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// Clear given frame rectangle to transparent.
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static void ZeroFillFrameRect(uint8_t* buf, int buf_stride, int x_offset,
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int y_offset, int width, int height) {
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int j;
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assert(width * NUM_CHANNELS <= buf_stride);
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buf += y_offset * buf_stride + x_offset * NUM_CHANNELS;
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for (j = 0; j < height; ++j) {
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memset(buf, 0, width * NUM_CHANNELS);
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buf += buf_stride;
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}
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}
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// Copy width * height pixels from 'src' to 'dst'.
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static int CopyCanvas(const uint8_t* src, uint8_t* dst,
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uint32_t width, uint32_t height) {
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const uint64_t size = (uint64_t)width * height * NUM_CHANNELS;
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if (size != (size_t)size) return 0;
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assert(src != NULL && dst != NULL);
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memcpy(dst, src, (size_t)size);
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return 1;
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}
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// Returns true if the current frame is a key-frame.
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static int IsKeyFrame(const WebPIterator* const curr,
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const WebPIterator* const prev,
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int prev_frame_was_key_frame,
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int canvas_width, int canvas_height) {
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if (curr->frame_num == 1) {
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return 1;
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} else if ((!curr->has_alpha || curr->blend_method == WEBP_MUX_NO_BLEND) &&
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IsFullFrame(curr->width, curr->height,
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canvas_width, canvas_height)) {
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return 1;
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} else {
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return (prev->dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) &&
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(IsFullFrame(prev->width, prev->height, canvas_width,
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canvas_height) ||
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prev_frame_was_key_frame);
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}
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}
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// Blend a single channel of 'src' over 'dst', given their alpha channel values.
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// 'src' and 'dst' are assumed to be NOT pre-multiplied by alpha.
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static uint8_t BlendChannelNonPremult(uint32_t src, uint8_t src_a,
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uint32_t dst, uint8_t dst_a,
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uint32_t scale, int shift) {
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const uint8_t src_channel = (src >> shift) & 0xff;
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const uint8_t dst_channel = (dst >> shift) & 0xff;
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const uint32_t blend_unscaled = src_channel * src_a + dst_channel * dst_a;
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assert(blend_unscaled < (1ULL << 32) / scale);
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return (blend_unscaled * scale) >> 24;
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}
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// Blend 'src' over 'dst' assuming they are NOT pre-multiplied by alpha.
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static uint32_t BlendPixelNonPremult(uint32_t src, uint32_t dst) {
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const uint8_t src_a = (src >> 24) & 0xff;
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if (src_a == 0) {
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return dst;
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} else {
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const uint8_t dst_a = (dst >> 24) & 0xff;
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// This is the approximate integer arithmetic for the actual formula:
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// dst_factor_a = (dst_a * (255 - src_a)) / 255.
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const uint8_t dst_factor_a = (dst_a * (256 - src_a)) >> 8;
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const uint8_t blend_a = src_a + dst_factor_a;
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const uint32_t scale = (1UL << 24) / blend_a;
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const uint8_t blend_r =
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BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 0);
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const uint8_t blend_g =
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BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 8);
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const uint8_t blend_b =
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BlendChannelNonPremult(src, src_a, dst, dst_factor_a, scale, 16);
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assert(src_a + dst_factor_a < 256);
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return (blend_r << 0) |
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(blend_g << 8) |
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(blend_b << 16) |
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((uint32_t)blend_a << 24);
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}
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}
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// Blend 'num_pixels' in 'src' over 'dst' assuming they are NOT pre-multiplied
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// by alpha.
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static void BlendPixelRowNonPremult(uint32_t* const src,
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const uint32_t* const dst, int num_pixels) {
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int i;
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for (i = 0; i < num_pixels; ++i) {
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const uint8_t src_alpha = (src[i] >> 24) & 0xff;
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if (src_alpha != 0xff) {
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src[i] = BlendPixelNonPremult(src[i], dst[i]);
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}
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}
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}
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// Individually multiply each channel in 'pix' by 'scale'.
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static WEBP_INLINE uint32_t ChannelwiseMultiply(uint32_t pix, uint32_t scale) {
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uint32_t mask = 0x00FF00FF;
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uint32_t rb = ((pix & mask) * scale) >> 8;
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uint32_t ag = ((pix >> 8) & mask) * scale;
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return (rb & mask) | (ag & ~mask);
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}
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// Blend 'src' over 'dst' assuming they are pre-multiplied by alpha.
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static uint32_t BlendPixelPremult(uint32_t src, uint32_t dst) {
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const uint8_t src_a = (src >> 24) & 0xff;
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return src + ChannelwiseMultiply(dst, 256 - src_a);
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}
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// Blend 'num_pixels' in 'src' over 'dst' assuming they are pre-multiplied by
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// alpha.
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static void BlendPixelRowPremult(uint32_t* const src, const uint32_t* const dst,
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int num_pixels) {
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int i;
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for (i = 0; i < num_pixels; ++i) {
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const uint8_t src_alpha = (src[i] >> 24) & 0xff;
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if (src_alpha != 0xff) {
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src[i] = BlendPixelPremult(src[i], dst[i]);
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}
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}
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}
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// Returns two ranges (<left, width> pairs) at row 'canvas_y', that belong to
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// 'src' but not 'dst'. A point range is empty if the corresponding width is 0.
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static void FindBlendRangeAtRow(const WebPIterator* const src,
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const WebPIterator* const dst, int canvas_y,
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int* const left1, int* const width1,
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int* const left2, int* const width2) {
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const int src_max_x = src->x_offset + src->width;
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const int dst_max_x = dst->x_offset + dst->width;
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const int dst_max_y = dst->y_offset + dst->height;
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assert(canvas_y >= src->y_offset && canvas_y < (src->y_offset + src->height));
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*left1 = -1;
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*width1 = 0;
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*left2 = -1;
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*width2 = 0;
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if (canvas_y < dst->y_offset || canvas_y >= dst_max_y ||
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src->x_offset >= dst_max_x || src_max_x <= dst->x_offset) {
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*left1 = src->x_offset;
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*width1 = src->width;
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return;
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}
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if (src->x_offset < dst->x_offset) {
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*left1 = src->x_offset;
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*width1 = dst->x_offset - src->x_offset;
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}
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if (src_max_x > dst_max_x) {
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*left2 = dst_max_x;
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*width2 = src_max_x - dst_max_x;
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}
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}
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int WebPAnimDecoderGetNext(WebPAnimDecoder* dec,
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uint8_t** buf_ptr, int* timestamp_ptr) {
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WebPIterator iter;
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uint32_t width;
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uint32_t height;
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int is_key_frame;
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int timestamp;
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BlendRowFunc blend_row;
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if (dec == NULL || buf_ptr == NULL || timestamp_ptr == NULL) return 0;
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if (!WebPAnimDecoderHasMoreFrames(dec)) return 0;
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width = dec->info_.canvas_width;
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height = dec->info_.canvas_height;
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blend_row = dec->blend_func_;
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// Get compressed frame.
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if (!WebPDemuxGetFrame(dec->demux_, dec->next_frame_, &iter)) {
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return 0;
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}
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timestamp = dec->prev_frame_timestamp_ + iter.duration;
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// Initialize.
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is_key_frame = IsKeyFrame(&iter, &dec->prev_iter_,
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dec->prev_frame_was_keyframe_, width, height);
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if (is_key_frame) {
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if (!ZeroFillCanvas(dec->curr_frame_, width, height)) {
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goto Error;
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}
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} else {
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if (!CopyCanvas(dec->prev_frame_disposed_, dec->curr_frame_,
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width, height)) {
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goto Error;
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}
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}
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// Decode.
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{
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const uint8_t* in = iter.fragment.bytes;
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const size_t in_size = iter.fragment.size;
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const size_t out_offset =
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(iter.y_offset * width + iter.x_offset) * NUM_CHANNELS;
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WebPDecoderConfig* const config = &dec->config_;
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WebPRGBABuffer* const buf = &config->output.u.RGBA;
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buf->stride = NUM_CHANNELS * width;
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buf->size = buf->stride * iter.height;
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buf->rgba = dec->curr_frame_ + out_offset;
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if (WebPDecode(in, in_size, config) != VP8_STATUS_OK) {
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goto Error;
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}
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}
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// During the decoding of current frame, we may have set some pixels to be
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// transparent (i.e. alpha < 255). However, the value of each of these
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// pixels should have been determined by blending it against the value of
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// that pixel in the previous frame if blending method of is WEBP_MUX_BLEND.
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if (iter.frame_num > 1 && iter.blend_method == WEBP_MUX_BLEND &&
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!is_key_frame) {
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if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_NONE) {
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int y;
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// Blend transparent pixels with pixels in previous canvas.
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for (y = 0; y < iter.height; ++y) {
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const size_t offset =
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(iter.y_offset + y) * width + iter.x_offset;
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blend_row((uint32_t*)dec->curr_frame_ + offset,
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(uint32_t*)dec->prev_frame_disposed_ + offset, iter.width);
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}
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} else {
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int y;
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assert(dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND);
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// We need to blend a transparent pixel with its value just after
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// initialization. That is, blend it with:
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// * Fully transparent pixel if it belongs to prevRect <-- No-op.
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// * The pixel in the previous canvas otherwise <-- Need alpha-blending.
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for (y = 0; y < iter.height; ++y) {
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const int canvas_y = iter.y_offset + y;
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int left1, width1, left2, width2;
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FindBlendRangeAtRow(&iter, &dec->prev_iter_, canvas_y, &left1, &width1,
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&left2, &width2);
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if (width1 > 0) {
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const size_t offset1 = canvas_y * width + left1;
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blend_row((uint32_t*)dec->curr_frame_ + offset1,
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(uint32_t*)dec->prev_frame_disposed_ + offset1, width1);
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}
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if (width2 > 0) {
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const size_t offset2 = canvas_y * width + left2;
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blend_row((uint32_t*)dec->curr_frame_ + offset2,
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(uint32_t*)dec->prev_frame_disposed_ + offset2, width2);
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}
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}
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}
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}
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// Update info of the previous frame and dispose it for the next iteration.
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dec->prev_frame_timestamp_ = timestamp;
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WebPDemuxReleaseIterator(&dec->prev_iter_);
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dec->prev_iter_ = iter;
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dec->prev_frame_was_keyframe_ = is_key_frame;
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CopyCanvas(dec->curr_frame_, dec->prev_frame_disposed_, width, height);
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if (dec->prev_iter_.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
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ZeroFillFrameRect(dec->prev_frame_disposed_, width * NUM_CHANNELS,
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dec->prev_iter_.x_offset, dec->prev_iter_.y_offset,
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dec->prev_iter_.width, dec->prev_iter_.height);
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}
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++dec->next_frame_;
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// All OK, fill in the values.
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*buf_ptr = dec->curr_frame_;
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*timestamp_ptr = timestamp;
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return 1;
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Error:
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WebPDemuxReleaseIterator(&iter);
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return 0;
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}
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int WebPAnimDecoderHasMoreFrames(const WebPAnimDecoder* dec) {
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if (dec == NULL) return 0;
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return (dec->next_frame_ <= (int)dec->info_.frame_count);
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}
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void WebPAnimDecoderReset(WebPAnimDecoder* dec) {
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if (dec != NULL) {
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dec->prev_frame_timestamp_ = 0;
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WebPDemuxReleaseIterator(&dec->prev_iter_);
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memset(&dec->prev_iter_, 0, sizeof(dec->prev_iter_));
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dec->prev_frame_was_keyframe_ = 0;
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dec->next_frame_ = 1;
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}
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}
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const WebPDemuxer* WebPAnimDecoderGetDemuxer(const WebPAnimDecoder* dec) {
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if (dec == NULL) return NULL;
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return dec->demux_;
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}
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void WebPAnimDecoderDelete(WebPAnimDecoder* dec) {
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if (dec != NULL) {
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WebPDemuxReleaseIterator(&dec->prev_iter_);
|
|
WebPDemuxDelete(dec->demux_);
|
|
WebPSafeFree(dec->curr_frame_);
|
|
WebPSafeFree(dec->prev_frame_disposed_);
|
|
WebPSafeFree(dec);
|
|
}
|
|
}
|