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Some bug-fixes for images with alpha.

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- Fix the off-by-one diff when cropping with simple-filter.
- Fix a bug in incremental decoding in case of alpha.
- In VP8FinishRow(), do not decode alpha when y_start > y_end.
- Correct output of alpha channel for MODE_ARGB.
- Correct output of alpha channel for MODE_RGBA_4444.

Change-Id: I785763a2a704b973cc742ad93ffbb53699d1fc0a
This commit is contained in:
Urvang Joshi
2011-12-07 15:01:35 +05:30
parent 273a12a013
commit 8666a93aae
5 changed files with 84 additions and 10 deletions
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61
src/dec/io.c
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@ -51,7 +51,9 @@ static int EmitSampledRGB(const VP8Io* const io, WebPDecParams* const p) {
const uint8_t* y_src = io->y;
const uint8_t* u_src = io->u;
const uint8_t* v_src = io->v;
const WebPSampleLinePairFunc sample = WebPSamplers[output->colorspace];
const WebPSampleLinePairFunc sample =
io->a ? WebPSamplersKeepAlpha[output->colorspace]
: WebPSamplers[output->colorspace];
const int mb_w = io->mb_w;
const int last = io->mb_h - 1;
int j;
@ -185,12 +187,34 @@ static int EmitAlphaRGB(const VP8Io* const io, WebPDecParams* const p) {
const int mb_h = io->mb_h;
int i, j;
const WebPRGBABuffer* const buf = &p->output->u.RGBA;
uint8_t* dst = buf->rgba + io->mb_y * buf->stride;
uint8_t* dst = buf->rgba + io->mb_y * buf->stride +
(p->output->colorspace == MODE_ARGB ? 0 : 3);
const uint8_t* alpha = io->a;
if (alpha) {
for (j = 0; j < mb_h; ++j) {
for (i = 0; i < mb_w; ++i) {
dst[4 * i + 3] = alpha[i];
dst[4 * i] = alpha[i];
}
alpha += io->width;
dst += buf->stride;
}
}
return 0;
}
static int EmitAlphaRGBA4444(const VP8Io* const io, WebPDecParams* const p) {
const int mb_w = io->mb_w;
const int mb_h = io->mb_h;
int i, j;
const WebPRGBABuffer* const buf = &p->output->u.RGBA;
uint8_t* dst = buf->rgba + io->mb_y * buf->stride + 1;
const uint8_t* alpha = io->a;
if (alpha) {
for (j = 0; j < mb_h; ++j) {
for (i = 0; i < mb_w; ++i) {
// Fill in the alpha value (converted to 4 bits).
const uint8_t alpha_val = (alpha[i] + 8) >> 4;
dst[2 * i] = (dst[2 * i] & 0xf0) | alpha_val;
}
alpha += io->width;
dst += buf->stride;
@ -440,14 +464,34 @@ static int EmitRescaledRGB(const VP8Io* const io, WebPDecParams* const p) {
static int ExportAlpha(WebPDecParams* const p, int y_pos) {
const WebPRGBABuffer* const buf = &p->output->u.RGBA;
uint8_t* dst = buf->rgba + (p->last_y + y_pos) * buf->stride;
uint8_t* dst = buf->rgba + (p->last_y + y_pos) * buf->stride +
(p->output->colorspace == MODE_ARGB ? 0 : 3);
int num_lines_out = 0;
while (p->scaler_a.y_accum <= 0) {
int i;
assert(p->last_y + y_pos + num_lines_out < p->output->height);
ExportRow(&p->scaler_a);
for (i = 0; i < p->scaler_a.dst_width; ++i) {
dst[4 * i + 3] = p->scaler_a.dst[i];
dst[4 * i] = p->scaler_a.dst[i];
}
dst += buf->stride;
num_lines_out++;
}
return num_lines_out;
}
static int ExportAlphaRGBA4444(WebPDecParams* const p, int y_pos) {
const WebPRGBABuffer* const buf = &p->output->u.RGBA;
uint8_t* dst = buf->rgba + (p->last_y + y_pos) * buf->stride + 1;
int num_lines_out = 0;
while (p->scaler_a.y_accum <= 0) {
int i;
assert(p->last_y + y_pos + num_lines_out < p->output->height);
ExportRow(&p->scaler_a);
for (i = 0; i < p->scaler_a.dst_width; ++i) {
// Fill in the alpha value (converted to 4 bits).
const uint8_t alpha_val = (p->scaler_a.dst[i] + 8) >> 4;
dst[2 * i] = (dst[2 * i] & 0xf0) | alpha_val;
}
dst += buf->stride;
num_lines_out++;
@ -460,7 +504,8 @@ static int EmitRescaledAlphaRGB(const VP8Io* const io, WebPDecParams* const p) {
int j = 0, pos = 0;
while (j < io->mb_h) {
j += Import(io->a + j * io->width, io->width, io->mb_h - j, &p->scaler_a);
pos += ExportAlpha(p, pos);
pos += (p->output->colorspace == MODE_RGBA_4444) ?
ExportAlphaRGBA4444(p, pos) : ExportAlpha(p, pos);
}
}
return 0;
@ -608,7 +653,9 @@ static int CustomSetup(VP8Io* io) {
}
if (IsAlphaMode(p->output->colorspace)) {
// We need transparency output
p->emit_alpha = is_rgb ? EmitAlphaRGB : EmitAlphaYUV;
p->emit_alpha =
is_rgb ? (p->output->colorspace == MODE_RGBA_4444 ?
EmitAlphaRGBA4444 : EmitAlphaRGB) : EmitAlphaYUV;
}
}