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lossy decoding: correct alpha-rescaling for YUVA format

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The luminance needs to be pre- and post- multiplied by
the alpha value in case of rescaling, for proper averaging.

Also:
- removed util/alpha_processing and moved it to dsp/
- removed WebPInitPremultiply() which was mostly useless
and merged it with the new function WebPInitAlphaProcessing()

Change-Id: If089cefd4ec53f6880a791c476fb1c7f7c5a8e60
This commit is contained in:
skal
2014-05-26 18:05:03 +02:00
committed by Gerrit Code Review
parent 78c12ed8e6
commit 399b916d27
14 changed files with 193 additions and 227 deletions
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36
src/dec/io.c
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@ -280,7 +280,17 @@ static int Rescale(const uint8_t* src, int src_stride,
static int EmitRescaledYUV(const VP8Io* const io, WebPDecParams* const p) {
const int mb_h = io->mb_h;
const int uv_mb_h = (mb_h + 1) >> 1;
const int num_lines_out = Rescale(io->y, io->y_stride, mb_h, &p->scaler_y);
WebPRescaler* const scaler = &p->scaler_y;
int num_lines_out = 0;
if (WebPIsAlphaMode(p->output->colorspace) && io->a != NULL) {
// Before rescaling, we premultiply the luma directly into the io->y
// internal buffer. This is OK since these samples are not used for
// intra-prediction (the top samples are saved in cache_y_/u_/v_).
// But we need to cast the const away, though.
WebPMultRows((uint8_t*)io->y, io->y_stride,
io->a, io->width, io->mb_w, mb_h, 0);
}
num_lines_out = Rescale(io->y, io->y_stride, mb_h, scaler);
Rescale(io->u, io->uv_stride, uv_mb_h, &p->scaler_u);
Rescale(io->v, io->uv_stride, uv_mb_h, &p->scaler_v);
return num_lines_out;
@ -288,7 +298,14 @@ static int EmitRescaledYUV(const VP8Io* const io, WebPDecParams* const p) {
static int EmitRescaledAlphaYUV(const VP8Io* const io, WebPDecParams* const p) {
if (io->a != NULL) {
Rescale(io->a, io->width, io->mb_h, &p->scaler_a);
const WebPYUVABuffer* const buf = &p->output->u.YUVA;
uint8_t* dst_y = buf->y + p->last_y * buf->y_stride;
const uint8_t* src_a = buf->a + p->last_y * buf->a_stride;
const int num_lines_out = Rescale(io->a, io->width, io->mb_h, &p->scaler_a);
if (num_lines_out > 0) { // unmultiply the Y
WebPMultRows(dst_y, buf->y_stride, src_a, buf->a_stride,
p->scaler_a.dst_width, num_lines_out, 1);
}
}
return 0;
}
@ -307,11 +324,11 @@ static int InitYUVRescaler(const VP8Io* const io, WebPDecParams* const p) {
size_t tmp_size;
int32_t* work;
tmp_size = work_size + 2 * uv_work_size;
tmp_size = (work_size + 2 * uv_work_size) * sizeof(*work);
if (has_alpha) {
tmp_size += work_size;
tmp_size += work_size * sizeof(*work);
}
p->memory = WebPSafeCalloc(1ULL, tmp_size * sizeof(*work));
p->memory = WebPSafeCalloc(1ULL, tmp_size);
if (p->memory == NULL) {
return 0; // memory error
}
@ -338,6 +355,7 @@ static int InitYUVRescaler(const VP8Io* const io, WebPDecParams* const p) {
io->mb_w, out_width, io->mb_h, out_height,
work + work_size + 2 * uv_work_size);
p->emit_alpha = EmitRescaledAlphaYUV;
WebPInitAlphaProcessing();
}
return 1;
}
@ -520,6 +538,7 @@ static int InitRGBRescaler(const VP8Io* const io, WebPDecParams* const p) {
} else {
p->emit_alpha_row = ExportAlpha;
}
WebPInitAlphaProcessing();
}
return 1;
}
@ -540,7 +559,9 @@ static int CustomSetup(VP8Io* io) {
if (!WebPIoInitFromOptions(p->options, io, is_alpha ? MODE_YUV : MODE_YUVA)) {
return 0;
}
if (is_alpha && WebPIsPremultipliedMode(colorspace)) WebPInitPremultiply();
if (is_alpha && WebPIsPremultipliedMode(colorspace)) {
WebPInitUpsamplers();
}
if (io->use_scaling) {
const int ok = is_rgb ? InitRGBRescaler(io, p) : InitYUVRescaler(io, p);
if (!ok) {
@ -574,6 +595,9 @@ static int CustomSetup(VP8Io* io) {
EmitAlphaRGBA4444
: is_rgb ? EmitAlphaRGB
: EmitAlphaYUV;
if (is_rgb) {
WebPInitAlphaProcessing();
}
}
}