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make WebPCleanupTransparentArea work with argb picture

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the -alpha_cleanup flag was ineffective since we switched cwebp
to using ARGB input always.

Original idea by David Eckel (dvdckl at gmail dot com)

Change-Id: I0917a8b91ce15a43199728ff4ee2a163be443bab
This commit is contained in:
skal 2014-01-17 20:19:16 +01:00
parent 5da185522b
commit c741183c10
2 changed files with 66 additions and 29 deletions
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55
src/enc/picture.c
View File

@ -992,7 +992,20 @@ static int is_transparent_area(const uint8_t* ptr, int stride, int size) {
return 1;
}
static WEBP_INLINE void flatten(uint8_t* ptr, int v, int stride, int size) {
static int is_transparent_argb_area(const uint32_t* ptr, int stride, int size) {
int y, x;
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) {
if (ptr[x] & 0xff000000u) {
return 0;
}
}
ptr += stride;
}
return 1;
}
static void flatten(uint8_t* ptr, int v, int stride, int size) {
int y;
for (y = 0; y < size; ++y) {
memset(ptr, v, size);
@ -1000,18 +1013,42 @@ static WEBP_INLINE void flatten(uint8_t* ptr, int v, int stride, int size) {
}
}
static void flatten_argb(uint32_t* ptr, uint32_t v, int stride, int size) {
int x, y;
for (y = 0; y < size; ++y) {
for (x = 0; x < size; ++x) ptr[x] = v;
ptr += stride;
}
}
void WebPCleanupTransparentArea(WebPPicture* pic) {
int x, y, w, h;
const uint8_t* a_ptr;
int values[3] = { 0 };
if (pic == NULL) return;
a_ptr = pic->a;
if (a_ptr == NULL) return; // nothing to do
w = pic->width / SIZE;
h = pic->height / SIZE;
// note: we ignore the left-overs on right/bottom
if (pic->use_argb) {
uint32_t argb_value = 0;
for (y = 0; y < h; ++y) {
int need_reset = 1;
for (x = 0; x < w; ++x) {
const int off = (y * pic->argb_stride + x) * SIZE;
if (is_transparent_argb_area(pic->argb + off, pic->argb_stride, SIZE)) {
if (need_reset) {
argb_value = pic->argb[off];
need_reset = 0;
}
flatten_argb(pic->argb + off, argb_value, pic->argb_stride, SIZE);
} else {
need_reset = 1;
}
}
}
} else {
const uint8_t* const a_ptr = pic->a;
int values[3] = { 0 };
if (a_ptr == NULL) return; // nothing to do
for (y = 0; y < h; ++y) {
int need_reset = 1;
for (x = 0; x < w; ++x) {
@ -1032,7 +1069,7 @@ void WebPCleanupTransparentArea(WebPPicture* pic) {
need_reset = 1;
}
}
// ignore the left-overs on right/bottom
}
}
}

6
src/webp/encode.h
View File

@ -459,9 +459,9 @@ WEBP_EXTERN(int) WebPPictureARGBToYUVADithered(
// Returns false in case of error.
WEBP_EXTERN(int) WebPPictureYUVAToARGB(WebPPicture* picture);
// Helper function: given a width x height plane of YUV(A) samples
// (with stride 'stride'), clean-up the YUV samples under fully transparent
// area, to help compressibility (no guarantee, though).
// Helper function: given a width x height plane of RGBA or YUV(A) samples
// clean-up the YUV or RGB samples under fully transparent area, to help
// compressibility (no guarantee, though).
WEBP_EXTERN(void) WebPCleanupTransparentArea(WebPPicture* picture);
// Scan the picture 'picture' for the presence of non fully opaque alpha values.