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gif2webp: Separate out each step into a method

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We now have ReadFrame(), OptimizeFrame(), EncodeFrame() and
DisposeFrame()
methods.

Change-Id: I522834bad18dd6a7a3ddac7c00dfd829c48248f8
This commit is contained in:
Urvang Joshi 2013-08-22 11:14:51 -07:00
parent bef7e9ccd1
commit 3b80bc4859
1 changed files with 89 additions and 49 deletions
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138
examples/gif2webp.c
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@ -34,7 +34,13 @@
//------------------------------------------------------------------------------
static int transparent_index = -1; // No transparency by default.
// Global variables gathered in a struct.
static struct {
int transparent_index; // Index of transparent color in the color map.
int is_first_frame;
size_t count_since_key_frame; // Frames seen since the last key frame.
size_t key_frame_interval; // Max distance between key frames.
} kParams;
static void ClearRectangle(WebPPicture* const picture,
int left, int top, int width, int height) {
@ -104,7 +110,7 @@ static void Remap(const uint8_t* const src, const GifFileType* const gif,
for (i = 0; i < len; ++i) {
const GifColorType c = colors[src[i]];
dst[i] = (src[i] == transparent_index) ? TRANSPARENT_COLOR
dst[i] = (src[i] == kParams.transparent_index) ? TRANSPARENT_COLOR
: c.Blue | (c.Green << 8) | (c.Red << 16) | (0xff << 24);
}
}
@ -117,6 +123,8 @@ static int IsKeyFrame(const WebPPicture* const curr,
int i, j;
int is_key_frame = 1;
if (kParams.is_first_frame) return 1;
// If previous canvas (with previous frame disposed) is all transparent,
// current frame is a key frame.
for (i = 0; i < prev->width; ++i) {
@ -183,11 +191,9 @@ static void ConvertToKeyFrame(WebPPicture* const curr,
rect->height = curr->height;
}
static int ReadSubImage(GifFileType* gif, WebPPicture* const prev,
int is_first_frame, size_t key_frame_interval,
size_t* const count_since_key_frame,
WebPFrameRect* const gif_rect, WebPPicture* sub_image,
WebPMuxFrameInfo* const info, WebPPicture* const curr) {
// Read the GIF image frame.
static int ReadFrame(GifFileType* const gif, WebPFrameRect* const gif_rect,
WebPPicture* const sub_image, WebPPicture* const curr) {
const GifImageDesc image_desc = gif->Image;
uint32_t* dst = NULL;
uint8_t* tmp = NULL;
@ -229,6 +235,19 @@ static int ReadSubImage(GifFileType* gif, WebPPicture* const prev,
Remap(tmp, gif, dst + y * sub_image->argb_stride, rect.width);
}
}
ok = 1;
End:
free(tmp);
return ok;
}
// Optimize the image frame for WebP.
static void OptimizeFrame(const WebPFrameRect* const gif_rect,
WebPPicture* const curr, WebPPicture* const prev,
WebPPicture* const sub_image,
WebPMuxFrameInfo* const info) {
WebPFrameRect rect = *gif_rect;
// Snap to even offsets (and adjust dimensions if needed).
rect.width += (rect.x_offset & 1);
@ -237,17 +256,17 @@ static int ReadSubImage(GifFileType* gif, WebPPicture* const prev,
rect.y_offset &= ~1;
// Make this a key frame if needed.
if (is_first_frame || IsKeyFrame(curr, &rect, prev)) {
*count_since_key_frame = 0;
if (IsKeyFrame(curr, &rect, prev)) {
kParams.count_since_key_frame = 0;
} else {
++*count_since_key_frame;
if (*count_since_key_frame > key_frame_interval) {
++kParams.count_since_key_frame;
if (kParams.count_since_key_frame > kParams.key_frame_interval) {
ConvertToKeyFrame(curr, prev, &rect);
*count_since_key_frame = 0;
kParams.count_since_key_frame = 0;
}
}
if (*count_since_key_frame == 0) {
if (kParams.count_since_key_frame == 0) {
info->blend_method = WEBP_MUX_NO_BLEND; // Key frame, so no need to blend.
} else {
info->blend_method = WEBP_MUX_BLEND; // The blending method in GIF.
@ -266,16 +285,52 @@ static int ReadSubImage(GifFileType* gif, WebPPicture* const prev,
sub_image);
info->x_offset = rect.x_offset;
info->y_offset = rect.y_offset;
}
static int EncodeFrame(const WebPConfig* const config,
WebPPicture* const sub_image,
WebPData* const encoded_data) {
int ok = 0;
WebPMemoryWriter memory;
if (!config->lossless) {
// We need to call BGRA variant because of the way we do Remap(). Note
// that 'sub_image' will no longer be a view and own some memory.
if (!WebPPictureImportBGRA(
sub_image, (uint8_t*)sub_image->argb,
sub_image->argb_stride * sizeof(*sub_image->argb))) {
goto End;
}
sub_image->use_argb = 0;
} else {
sub_image->use_argb = 1;
}
sub_image->writer = WebPMemoryWrite;
sub_image->custom_ptr = &memory;
WebPMemoryWriterInit(&memory);
if (!WebPEncode(config, sub_image)) goto End;
encoded_data->bytes = memory.mem;
encoded_data->size = memory.size;
ok = 1;
End:
free(tmp);
return ok;
}
static void DisposeFrame(WebPMuxAnimDispose dispose_method,
const WebPFrameRect* const gif_rect,
WebPPicture* const frame, WebPPicture* const canvas) {
if (dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
ClearPicture(frame, NULL);
ClearPicture(canvas, gif_rect);
}
}
static int GetBackgroundColor(const ColorMapObject* const color_map,
GifWord bgcolor_idx, uint32_t* const bgcolor) {
if (transparent_index != -1 && bgcolor_idx == transparent_index) {
if (kParams.transparent_index != -1 &&
bgcolor_idx == kParams.transparent_index) {
*bgcolor = TRANSPARENT_COLOR; // Special case.
return 1;
} else if (color_map == NULL || color_map->Colors == NULL
@ -358,9 +413,6 @@ int main(int argc, const char *argv[]) {
WebPMuxFrameInfo frame;
WebPMuxAnimParams anim = { WHITE_COLOR, 0 };
int is_first_frame = 1;
size_t count_since_key_frame = 0; // Frames seen since the last key frame.
size_t key_frame_interval = 9; // Max distance between key frames.
int done;
int c;
int quiet = 0;
@ -370,6 +422,12 @@ int main(int argc, const char *argv[]) {
int stored_icc = 0; // Whether we have already stored an ICC profile.
int stored_xmp = 0;
// Initialize global variables.
kParams.transparent_index = -1; // No transparency by default.
kParams.is_first_frame = 1;
kParams.key_frame_interval = 9;
kParams.count_since_key_frame = 0;
memset(&frame, 0, sizeof(frame));
frame.id = WEBP_CHUNK_ANMF;
frame.dispose_method = WEBP_MUX_DISPOSE_BACKGROUND;
@ -400,8 +458,8 @@ int main(int argc, const char *argv[]) {
} else if (!strcmp(argv[c], "-m") && c < argc - 1) {
config.method = strtol(argv[++c], NULL, 0);
} else if (!strcmp(argv[c], "-kmax") && c < argc - 1) {
key_frame_interval = strtoul(argv[++c], NULL, 0);
if (key_frame_interval == 0) key_frame_interval = ~0;
kParams.key_frame_interval = strtoul(argv[++c], NULL, 0);
if (kParams.key_frame_interval == 0) kParams.key_frame_interval = ~0;
} else if (!strcmp(argv[c], "-f") && c < argc - 1) {
config.filter_strength = strtol(argv[++c], NULL, 0);
} else if (!strcmp(argv[c], "-version")) {
@ -467,31 +525,16 @@ int main(int argc, const char *argv[]) {
case IMAGE_DESC_RECORD_TYPE: {
WebPPicture sub_image;
WebPFrameRect gif_rect;
WebPMemoryWriter memory;
if (!DGifGetImageDesc(gif)) goto End;
if (!ReadSubImage(gif, &previous, is_first_frame, key_frame_interval,
&count_since_key_frame, &gif_rect, &sub_image, &frame,
&current)) {
if (!ReadFrame(gif, &gif_rect, &sub_image, &current)) {
goto End;
}
if (!config.lossless) {
// We need to call BGRA variant because of the way we do Remap(). Note
// that 'sub_image' will no longer be a view and own some memory.
WebPPictureImportBGRA(
&sub_image, (uint8_t*)sub_image.argb,
sub_image.argb_stride * sizeof(*sub_image.argb));
sub_image.use_argb = 0;
} else {
sub_image.use_argb = 1;
}
OptimizeFrame(&gif_rect, &current, &previous, &sub_image, &frame);
sub_image.writer = WebPMemoryWrite;
sub_image.custom_ptr = &memory;
WebPMemoryWriterInit(&memory);
if (!WebPEncode(&config, &sub_image)) {
fprintf(stderr, "Error! Cannot encode current as WebP\n");
if (!EncodeFrame(&config, &sub_image, &frame.bitstream)) {
fprintf(stderr, "Error! Cannot encode frame as WebP\n");
fprintf(stderr, "Error code: %d\n", sub_image.error_code);
goto End;
}
@ -499,8 +542,6 @@ int main(int argc, const char *argv[]) {
// Now we have all the info about the frame, as a Graphic Control
// Extension Block always appears before the Image Descriptor Block.
// So add the frame to mux.
frame.bitstream.bytes = memory.mem;
frame.bitstream.size = memory.size;
err = WebPMuxPushFrame(mux, &frame, 1);
if (err != WEBP_MUX_OK) {
fprintf(stderr, "ERROR (%s): Could not add animation frame.\n",
@ -513,16 +554,14 @@ int main(int argc, const char *argv[]) {
frame.x_offset, frame.y_offset,
frame.duration);
printf("dispose:%d blend:%d transparent index:%d\n",
frame.dispose_method, frame.blend_method, transparent_index);
frame.dispose_method, frame.blend_method,
kParams.transparent_index);
}
WebPDataClear(&frame.bitstream);
WebPPictureFree(&sub_image);
is_first_frame = 0;
kParams.is_first_frame = 0;
if (frame.dispose_method == WEBP_MUX_DISPOSE_BACKGROUND) {
ClearPicture(&current, NULL);
ClearPicture(&previous, &gif_rect);
}
DisposeFrame(frame.dispose_method, &gif_rect, &current, &previous);
break;
}
case EXTENSION_RECORD_TYPE: {
@ -551,8 +590,9 @@ int main(int argc, const char *argv[]) {
(dispose == 2) ? WEBP_MUX_DISPOSE_BACKGROUND
: WEBP_MUX_DISPOSE_NONE;
}
transparent_index = (flags & GIF_TRANSPARENT_MASK) ? data[4] : -1;
if (is_first_frame) {
kParams.transparent_index =
(flags & GIF_TRANSPARENT_MASK) ? data[4] : -1;
if (kParams.is_first_frame) {
if (!GetBackgroundColor(gif->SColorMap, gif->SBackGroundColor,
&anim.bgcolor)) {
fprintf(stderr, "GIF decode warning: invalid background color "