webp/examples/gif2webp_util.c

668 lines
23 KiB
C
Raw Normal View History

// Copyright 2013 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Helper structs and methods for gif2webp tool.
//
#include <assert.h>
#include <stdio.h>
#include "webp/encode.h"
#include "./gif2webp_util.h"
#define DELTA_INFINITY 1ULL << 32
#define KEYFRAME_NONE -1
//------------------------------------------------------------------------------
// Helper utilities.
static void ClearRectangle(WebPPicture* const picture,
int left, int top, int width, int height) {
int j;
for (j = top; j < top + height; ++j) {
uint32_t* const dst = picture->argb + j * picture->argb_stride;
int i;
for (i = left; i < left + width; ++i) {
dst[i] = WEBP_UTIL_TRANSPARENT_COLOR;
}
}
}
void WebPUtilClearPic(WebPPicture* const picture,
const WebPFrameRect* const rect) {
if (rect != NULL) {
ClearRectangle(picture, rect->x_offset, rect->y_offset,
rect->width, rect->height);
} else {
ClearRectangle(picture, 0, 0, picture->width, picture->height);
}
}
// TODO: Also used in picture.c. Move to a common location?
// Copy width x height pixels from 'src' to 'dst' honoring the strides.
static void CopyPlane(const uint8_t* src, int src_stride,
uint8_t* dst, int dst_stride, int width, int height) {
while (height-- > 0) {
memcpy(dst, src, width);
src += src_stride;
dst += dst_stride;
}
}
// Copy pixels from 'src' to 'dst' honoring strides. 'src' and 'dst' are assumed
// to be already allocated.
static void CopyPixels(const WebPPicture* const src, WebPPicture* const dst) {
assert(src->width == dst->width && src->height == dst->height);
CopyPlane((uint8_t*)src->argb, 4 * src->argb_stride, (uint8_t*)dst->argb,
4 * dst->argb_stride, 4 * src->width, src->height);
}
// Given 'src' picture and its frame rectangle 'rect', blend it into 'dst'.
static void BlendPixels(const WebPPicture* const src,
const WebPFrameRect* const rect,
WebPPicture* const dst) {
int j;
assert(src->width == dst->width && src->height == dst->height);
for (j = rect->y_offset; j < rect->y_offset + rect->height; ++j) {
int i;
for (i = rect->x_offset; i < rect->x_offset + rect->width; ++i) {
const uint32_t src_pixel = src->argb[j * src->argb_stride + i];
const int src_alpha = src_pixel >> 24;
if (src_alpha != 0) {
dst->argb[j * dst->argb_stride + i] = src_pixel;
}
}
}
}
// Replace transparent pixels within 'dst_rect' of 'dst' by those in the 'src'.
static void ReduceTransparency(const WebPPicture* const src,
const WebPFrameRect* const rect,
WebPPicture* const dst) {
int i, j;
assert(src != NULL && dst != NULL && rect != NULL);
assert(src->width == dst->width && src->height == dst->height);
for (j = rect->y_offset; j < rect->y_offset + rect->height; ++j) {
for (i = rect->x_offset; i < rect->x_offset + rect->width; ++i) {
const uint32_t src_pixel = src->argb[j * src->argb_stride + i];
const int src_alpha = src_pixel >> 24;
const uint32_t dst_pixel = dst->argb[j * dst->argb_stride + i];
const int dst_alpha = dst_pixel >> 24;
if (dst_alpha == 0 && src_alpha == 0xff) {
dst->argb[j * dst->argb_stride + i] = src_pixel;
}
}
}
}
// Replace similar blocks of pixels by a 'see-through' transparent block
// with uniform average color.
static void FlattenSimilarBlocks(const WebPPicture* const src,
const WebPFrameRect* const rect,
WebPPicture* const dst) {
int i, j;
const int block_size = 8;
const int y_start = (rect->y_offset + block_size) & ~(block_size - 1);
const int y_end = (rect->y_offset + rect->height) & ~(block_size - 1);
const int x_start = (rect->x_offset + block_size) & ~(block_size - 1);
const int x_end = (rect->x_offset + rect->width) & ~(block_size - 1);
assert(src != NULL && dst != NULL && rect != NULL);
assert(src->width == dst->width && src->height == dst->height);
assert((block_size & (block_size - 1)) == 0); // must be a power of 2
// Iterate over each block and count similar pixels.
for (j = y_start; j < y_end; j += block_size) {
for (i = x_start; i < x_end; i += block_size) {
int cnt = 0;
int avg_r = 0, avg_g = 0, avg_b = 0;
int x, y;
const uint32_t* const psrc = src->argb + j * src->argb_stride + i;
uint32_t* const pdst = dst->argb + j * dst->argb_stride + i;
for (y = 0; y < block_size; ++y) {
for (x = 0; x < block_size; ++x) {
const uint32_t src_pixel = psrc[x + y * src->argb_stride];
const int alpha = src_pixel >> 24;
if (alpha == 0xff &&
src_pixel == pdst[x + y * dst->argb_stride]) {
++cnt;
avg_r += (src_pixel >> 16) & 0xff;
avg_g += (src_pixel >> 8) & 0xff;
avg_b += (src_pixel >> 0) & 0xff;
}
}
}
// If we have a fully similar block, we replace it with an
// average transparent block. This compresses better in lossy mode.
if (cnt == block_size * block_size) {
const uint32_t color = (0x00 << 24) |
((avg_r / cnt) << 16) |
((avg_g / cnt) << 8) |
((avg_b / cnt) << 0);
for (y = 0; y < block_size; ++y) {
for (x = 0; x < block_size; ++x) {
pdst[x + y * dst->argb_stride] = color;
}
}
}
}
}
}
//------------------------------------------------------------------------------
// Key frame related utilities.
// Returns true if 'curr' frame with frame rectangle 'curr_rect' is a key frame,
// that is, it can be decoded independently of 'prev' canvas.
static int IsKeyFrame(const WebPPicture* const curr,
const WebPFrameRect* const curr_rect,
const WebPPicture* const prev) {
int i, j;
int is_key_frame = 1;
// If previous canvas (with previous frame disposed) is all transparent,
// current frame is a key frame.
for (i = 0; i < prev->width; ++i) {
for (j = 0; j < prev->height; ++j) {
const uint32_t prev_alpha = (prev->argb[j * prev->argb_stride + i]) >> 24;
if (prev_alpha != 0) {
is_key_frame = 0;
break;
}
}
if (!is_key_frame) break;
}
if (is_key_frame) return 1;
// If current frame covers the whole canvas and does not contain any
// transparent pixels that depend on previous canvas, then current frame is
// a key frame.
if (curr_rect->width == curr->width && curr_rect->height == curr->height) {
assert(curr_rect->x_offset == 0 && curr_rect->y_offset == 0);
is_key_frame = 1;
for (j = 0; j < prev->height; ++j) {
for (i = 0; i < prev->width; ++i) {
const uint32_t prev_alpha =
(prev->argb[j * prev->argb_stride + i]) >> 24;
const uint32_t curr_alpha =
(curr->argb[j * curr->argb_stride + i]) >> 24;
if (curr_alpha != 0xff && prev_alpha != 0) {
is_key_frame = 0;
break;
}
}
if (!is_key_frame) break;
}
if (is_key_frame) return 1;
}
return 0;
}
// Given 'prev' frame and current frame rectangle 'rect', convert 'curr' frame
// to a key frame.
static void ConvertToKeyFrame(const WebPPicture* const prev,
WebPFrameRect* const rect,
WebPPicture* const curr) {
int j;
assert(curr->width == prev->width && curr->height == prev->height);
// Replace transparent pixels of current canvas with those from previous
// canvas (with previous frame disposed).
for (j = 0; j < curr->height; ++j) {
int i;
for (i = 0; i < curr->width; ++i) {
uint32_t* const curr_pixel = curr->argb + j * curr->argb_stride + i;
const int curr_alpha = *curr_pixel >> 24;
if (curr_alpha == 0) {
*curr_pixel = prev->argb[j * prev->argb_stride + i];
}
}
}
// Frame rectangle now covers the whole canvas.
rect->x_offset = 0;
rect->y_offset = 0;
rect->width = curr->width;
rect->height = curr->height;
}
//------------------------------------------------------------------------------
// Encoded frame.
// Used to store two candidates of encoded data for an animation frame. One of
// the two will be chosen later.
typedef struct {
WebPMuxFrameInfo sub_frame; // Encoded frame rectangle.
WebPMuxFrameInfo key_frame; // Encoded frame if it was converted to keyframe.
} EncodedFrame;
// Release the data contained by 'encoded_frame'.
static void FrameRelease(EncodedFrame* const encoded_frame) {
if (encoded_frame != NULL) {
WebPDataClear(&encoded_frame->sub_frame.bitstream);
WebPDataClear(&encoded_frame->key_frame.bitstream);
memset(encoded_frame, 0, sizeof(*encoded_frame));
}
}
//------------------------------------------------------------------------------
// Frame cache.
// Used to store encoded frames that haven't been output yet.
struct WebPFrameCache {
EncodedFrame* encoded_frames; // Array of encoded frames.
size_t size; // Number of allocated data elements.
size_t start; // Start index.
size_t count; // Number of valid data elements.
int flush_count; // If >0, flush_count frames starting from
// 'start' are ready to be added to mux.
int64_t best_delta; // min(canvas size - frame size) over the frames.
// Can be negative in certain cases due to
// transparent pixels in a frame.
int keyframe; // Index of selected keyframe relative to 'start'.
size_t kmin; // Min distance between key frames.
size_t kmax; // Max distance between key frames.
size_t count_since_key_frame; // Frames seen since the last key frame.
int allow_mixed; // If true, each frame can be lossy or lossless.
WebPPicture prev_canvas; // Previous canvas (properly disposed).
WebPPicture curr_canvas; // Current canvas (temporary buffer).
int is_first_frame; // True if no frames have been added to the cache
// since WebPFrameCacheNew().
};
// Reset the counters in the cache struct. Doesn't touch 'cache->encoded_frames'
// and 'cache->size'.
static void CacheReset(WebPFrameCache* const cache) {
cache->start = 0;
cache->count = 0;
cache->flush_count = 0;
cache->best_delta = DELTA_INFINITY;
cache->keyframe = KEYFRAME_NONE;
}
WebPFrameCache* WebPFrameCacheNew(int width, int height,
size_t kmin, size_t kmax, int allow_mixed) {
WebPFrameCache* cache = (WebPFrameCache*)malloc(sizeof(*cache));
if (cache == NULL) return NULL;
CacheReset(cache);
// sanity init, so we can call WebPFrameCacheDelete():
cache->encoded_frames = NULL;
cache->is_first_frame = 1;
// Picture buffers.
if (!WebPPictureInit(&cache->prev_canvas) ||
!WebPPictureInit(&cache->curr_canvas)) {
return NULL;
}
cache->prev_canvas.width = width;
cache->prev_canvas.height = height;
cache->prev_canvas.use_argb = 1;
if (!WebPPictureAlloc(&cache->prev_canvas) ||
!WebPPictureCopy(&cache->prev_canvas, &cache->curr_canvas)) {
goto Err;
}
WebPUtilClearPic(&cache->prev_canvas, NULL);
// Cache data.
cache->allow_mixed = allow_mixed;
cache->kmin = kmin;
cache->kmax = kmax;
cache->count_since_key_frame = 0;
assert(kmax > kmin);
cache->size = kmax - kmin;
cache->encoded_frames =
(EncodedFrame*)calloc(cache->size, sizeof(*cache->encoded_frames));
if (cache->encoded_frames == NULL) goto Err;
return cache; // All OK.
Err:
WebPFrameCacheDelete(cache);
return NULL;
}
void WebPFrameCacheDelete(WebPFrameCache* const cache) {
if (cache != NULL) {
if (cache->encoded_frames != NULL) {
size_t i;
for (i = 0; i < cache->size; ++i) {
FrameRelease(&cache->encoded_frames[i]);
}
free(cache->encoded_frames);
}
WebPPictureFree(&cache->prev_canvas);
WebPPictureFree(&cache->curr_canvas);
free(cache);
}
}
static int EncodeFrame(const WebPConfig* const config, WebPPicture* const pic,
WebPMemoryWriter* const memory) {
pic->use_argb = 1;
pic->writer = WebPMemoryWrite;
pic->custom_ptr = memory;
if (!WebPEncode(config, pic)) {
return 0;
}
return 1;
}
static void GetEncodedData(const WebPMemoryWriter* const memory,
WebPData* const encoded_data) {
encoded_data->bytes = memory->mem;
encoded_data->size = memory->size;
}
#define MIN_COLORS_LOSSY 31 // Don't try lossy below this threshold.
#define MAX_COLORS_LOSSLESS 194 // Don't try lossless above this threshold.
#define MAX_COLOR_COUNT 256 // Power of 2 greater than MAX_COLORS_LOSSLESS.
#define HASH_SIZE (MAX_COLOR_COUNT * 4)
#define HASH_RIGHT_SHIFT 22 // 32 - log2(HASH_SIZE).
// TODO(urvang): Also used in enc/vp8l.c. Move to utils.
// If the number of colors in the 'pic' is at least MAX_COLOR_COUNT, return
// MAX_COLOR_COUNT. Otherwise, return the exact number of colors in the 'pic'.
static int GetColorCount(const WebPPicture* const pic) {
int x, y;
int num_colors = 0;
uint8_t in_use[HASH_SIZE] = { 0 };
uint32_t colors[HASH_SIZE];
static const uint32_t kHashMul = 0x1e35a7bd;
const uint32_t* argb = pic->argb;
const int width = pic->width;
const int height = pic->height;
uint32_t last_pix = ~argb[0]; // so we're sure that last_pix != argb[0]
for (y = 0; y < height; ++y) {
for (x = 0; x < width; ++x) {
int key;
if (argb[x] == last_pix) {
continue;
}
last_pix = argb[x];
key = (kHashMul * last_pix) >> HASH_RIGHT_SHIFT;
while (1) {
if (!in_use[key]) {
colors[key] = last_pix;
in_use[key] = 1;
++num_colors;
if (num_colors >= MAX_COLOR_COUNT) {
return MAX_COLOR_COUNT; // Exact count not needed.
}
break;
} else if (colors[key] == last_pix) {
break; // The color is already there.
} else {
// Some other color sits here, so do linear conflict resolution.
++key;
key &= (HASH_SIZE - 1); // Key mask.
}
}
}
argb += pic->argb_stride;
}
return num_colors;
}
#undef MAX_COLOR_COUNT
#undef HASH_SIZE
#undef HASH_RIGHT_SHIFT
static int SetFrame(const WebPConfig* const config, int allow_mixed,
int is_key_frame, const WebPPicture* const prev_canvas,
WebPPicture* const frame, const WebPFrameRect* const rect,
const WebPMuxFrameInfo* const info,
WebPPicture* const sub_frame, EncodedFrame* encoded_frame) {
int try_lossless;
int try_lossy;
int try_both;
WebPMemoryWriter mem1, mem2;
WebPData* encoded_data;
WebPMuxFrameInfo* const dst =
is_key_frame ? &encoded_frame->key_frame : &encoded_frame->sub_frame;
*dst = *info;
encoded_data = &dst->bitstream;
WebPMemoryWriterInit(&mem1);
WebPMemoryWriterInit(&mem2);
if (!allow_mixed) {
try_lossless = config->lossless;
try_lossy = !try_lossless;
} else { // Use a heuristic for trying lossless and/or lossy compression.
const int num_colors = GetColorCount(sub_frame);
try_lossless = (num_colors < MAX_COLORS_LOSSLESS);
try_lossy = (num_colors >= MIN_COLORS_LOSSY);
}
try_both = try_lossless && try_lossy;
if (try_lossless) {
WebPConfig config_ll = *config;
config_ll.lossless = 1;
if (!EncodeFrame(&config_ll, sub_frame, &mem1)) {
goto Err;
}
}
if (try_lossy) {
WebPConfig config_lossy = *config;
config_lossy.lossless = 0;
if (!is_key_frame) {
// For lossy compression of a frame, it's better to replace transparent
// pixels of 'curr' with actual RGB values, whenever possible.
ReduceTransparency(prev_canvas, rect, frame);
// TODO(later): Investigate if this helps lossless compression as well.
FlattenSimilarBlocks(prev_canvas, rect, frame);
}
if (!EncodeFrame(&config_lossy, sub_frame, &mem2)) {
goto Err;
}
}
if (try_both) { // Pick the encoding with smallest size.
// TODO(later): Perhaps a rough SSIM/PSNR produced by the encoder should
// also be a criteria, in addition to sizes.
if (mem1.size <= mem2.size) {
WebPMemoryWriterClear(&mem2);
GetEncodedData(&mem1, encoded_data);
} else {
WebPMemoryWriterClear(&mem1);
GetEncodedData(&mem2, encoded_data);
}
} else {
GetEncodedData(try_lossless ? &mem1 : &mem2, encoded_data);
}
return 1;
Err:
WebPMemoryWriterClear(&mem1);
WebPMemoryWriterClear(&mem2);
return 0;
}
#undef MIN_COLORS_LOSSY
#undef MAX_COLORS_LOSSLESS
// Returns cached frame at given 'position' index.
static EncodedFrame* CacheGetFrame(const WebPFrameCache* const cache,
size_t position) {
assert(cache->start + position < cache->size);
return &cache->encoded_frames[cache->start + position];
}
// Calculate the penalty incurred if we encode given frame as a key frame
// instead of a sub-frame.
static int64_t KeyFramePenalty(const EncodedFrame* const encoded_frame) {
return ((int64_t)encoded_frame->key_frame.bitstream.size -
encoded_frame->sub_frame.bitstream.size);
}
static void DisposeFrame(WebPMuxAnimDispose dispose_method,
const WebPFrameRect* const gif_rect,
WebPPicture* const frame, WebPPicture* const canvas) {
if (dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
WebPUtilClearPic(frame, NULL);
WebPUtilClearPic(canvas, gif_rect);
}
}
int WebPFrameCacheAddFrame(WebPFrameCache* const cache,
const WebPConfig* const config,
const WebPFrameRect* const orig_rect,
WebPPicture* const frame,
WebPMuxFrameInfo* const info) {
int ok = 0;
WebPFrameRect rect = *orig_rect;
WebPPicture sub_image; // View extracted from 'frame' with rectangle 'rect'.
WebPPicture* const prev_canvas = &cache->prev_canvas;
const size_t position = cache->count;
const int allow_mixed = cache->allow_mixed;
EncodedFrame* const encoded_frame = CacheGetFrame(cache, position);
assert(position < cache->size);
// Snap to even offsets (and adjust dimensions if needed).
rect.width += (rect.x_offset & 1);
rect.height += (rect.y_offset & 1);
rect.x_offset &= ~1;
rect.y_offset &= ~1;
if (!WebPPictureView(frame, rect.x_offset, rect.y_offset,
rect.width, rect.height, &sub_image)) {
return 0;
}
info->x_offset = rect.x_offset;
info->y_offset = rect.y_offset;
++cache->count;
if (cache->is_first_frame || IsKeyFrame(frame, &rect, prev_canvas)) {
// Add this as a key frame.
if (!SetFrame(config, allow_mixed, 1, NULL, NULL, NULL, info, &sub_image,
encoded_frame)) {
goto End;
}
cache->keyframe = position;
cache->flush_count = cache->count;
cache->count_since_key_frame = 0;
// Update prev_canvas by simply copying from 'curr'.
CopyPixels(frame, prev_canvas);
} else {
++cache->count_since_key_frame;
if (cache->count_since_key_frame <= cache->kmin) {
// Add this as a frame rectangle.
if (!SetFrame(config, allow_mixed, 0, prev_canvas, frame, &rect, info,
&sub_image, encoded_frame)) {
goto End;
}
cache->flush_count = cache->count;
// Update prev_canvas by blending 'curr' into it.
BlendPixels(frame, orig_rect, prev_canvas);
} else {
WebPPicture full_image;
WebPMuxFrameInfo full_image_info;
int frame_added;
int64_t curr_delta;
// Add frame rectangle to cache.
if (!SetFrame(config, allow_mixed, 0, prev_canvas, frame, &rect, info,
&sub_image, encoded_frame)) {
goto End;
}
// Convert to a key frame.
CopyPixels(frame, &cache->curr_canvas);
ConvertToKeyFrame(prev_canvas, &rect, &cache->curr_canvas);
if (!WebPPictureView(&cache->curr_canvas, rect.x_offset, rect.y_offset,
rect.width, rect.height, &full_image)) {
goto End;
}
full_image_info = *info;
full_image_info.x_offset = rect.x_offset;
full_image_info.y_offset = rect.y_offset;
// Add key frame to cache, too.
frame_added = SetFrame(config, allow_mixed, 1, NULL, NULL, NULL,
&full_image_info, &full_image, encoded_frame);
WebPPictureFree(&full_image);
if (!frame_added) goto End;
// Analyze size difference of the two variants.
curr_delta = KeyFramePenalty(encoded_frame);
if (curr_delta <= cache->best_delta) { // Pick this as keyframe.
cache->keyframe = position;
cache->best_delta = curr_delta;
cache->flush_count = cache->count - 1; // We can flush previous frames.
}
if (cache->count_since_key_frame == cache->kmax) {
cache->flush_count = cache->count;
cache->count_since_key_frame = 0;
}
// Update prev_canvas by simply copying from 'curr_canvas'.
CopyPixels(&cache->curr_canvas, prev_canvas);
}
}
DisposeFrame(info->dispose_method, orig_rect, frame, prev_canvas);
cache->is_first_frame = 0;
ok = 1;
End:
WebPPictureFree(&sub_image);
if (!ok) {
FrameRelease(encoded_frame);
--cache->count; // We reset the count, as the frame addition failed.
}
return ok;
}
WebPMuxError WebPFrameCacheFlush(WebPFrameCache* const cache, int verbose,
WebPMux* const mux) {
while (cache->flush_count > 0) {
WebPMuxFrameInfo* info;
WebPMuxError err;
EncodedFrame* const curr = CacheGetFrame(cache, 0);
// Pick frame or full canvas.
if (cache->keyframe == 0) {
info = &curr->key_frame;
info->blend_method = WEBP_MUX_NO_BLEND;
cache->keyframe = KEYFRAME_NONE;
cache->best_delta = DELTA_INFINITY;
} else {
info = &curr->sub_frame;
info->blend_method = WEBP_MUX_BLEND;
}
// Add to mux.
err = WebPMuxPushFrame(mux, info, 1);
if (err != WEBP_MUX_OK) return err;
if (verbose) {
printf("Added frame. offset:%d,%d duration:%d dispose:%d blend:%d\n",
info->x_offset, info->y_offset, info->duration,
info->dispose_method, info->blend_method);
}
FrameRelease(curr);
++cache->start;
--cache->flush_count;
--cache->count;
if (cache->keyframe != KEYFRAME_NONE) --cache->keyframe;
}
if (cache->count == 0) CacheReset(cache);
return WEBP_MUX_OK;
}
WebPMuxError WebPFrameCacheFlushAll(WebPFrameCache* const cache, int verbose,
WebPMux* const mux) {
cache->flush_count = cache->count; // Force flushing of all frames.
return WebPFrameCacheFlush(cache, verbose, mux);
}
//------------------------------------------------------------------------------