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add colorspace for premultiplied alpha

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The new modes are
       MODE_rgbA
       MODE_bgrA
       MODE_Argb
       MODE_rgbA_4444
It's binary incompatible, since the enums changed.

While at it, i removed the now unneeded KeepAlpha methods.
-> Saved ~12k of code!

* made explicit mention that alpha_plane is persistent,
so we have access to the full alpha plane data at all time.
Incremental decoding of alpha was planned for, but not
implemented. So better not dragged this constaint for now
and make the code easier until we revisit that.

Change-Id: Idaba281a6ca819965ca062d1c23329f36d90c7ff
This commit is contained in:
Pascal Massimino
2012-06-04 07:40:32 -07:00
parent 5f7bb3f53a
commit 48f827574e
13 changed files with 303 additions and 122 deletions
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11
src/dec/buffer.c
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@ -22,7 +22,10 @@ extern "C" {
// WebPDecBuffer
// Number of bytes per pixel for the different color-spaces.
static const int kModeBpp[MODE_LAST] = { 3, 4, 3, 4, 4, 2, 2, 1, 1 };
static const int kModeBpp[MODE_LAST] = {
3, 4, 3, 4, 4, 2, 2,
4, 4, 4, 2, // pre-multiplied modes
1, 1 };
// Check that webp_csp_mode is within the bounds of WEBP_CSP_MODE.
// Convert to an integer to handle both the unsigned/signed enum cases
@ -38,7 +41,7 @@ static VP8StatusCode CheckDecBuffer(const WebPDecBuffer* const buffer) {
const int height = buffer->height;
if (!IsValidColorspace(mode)) {
ok = 0;
} else if (mode >= MODE_YUV) { // YUV checks
} else if (!WebPIsRGBMode(mode)) { // YUV checks
const WebPYUVABuffer* const buf = &buffer->u.YUVA;
const size_t size = buf->y_stride * height;
const size_t u_size = buf->u_stride * ((height + 1) / 2);
@ -81,7 +84,7 @@ static VP8StatusCode AllocateBuffer(WebPDecBuffer* const buffer) {
const int stride = w * kModeBpp[mode];
const uint64_t size = (uint64_t)stride * h;
if (mode >= MODE_YUV) {
if (!WebPIsRGBMode(mode)) {
uv_stride = (w + 1) / 2;
uv_size = (uint64_t)uv_stride * ((h + 1) / 2);
if (mode == MODE_YUVA) {
@ -101,7 +104,7 @@ static VP8StatusCode AllocateBuffer(WebPDecBuffer* const buffer) {
return VP8_STATUS_OUT_OF_MEMORY;
}
if (mode >= MODE_YUV) { // YUVA initialization
if (!WebPIsRGBMode(mode)) { // YUVA initialization
WebPYUVABuffer* const buf = &buffer->u.YUVA;
buf->y = output;
buf->y_stride = stride;