mirror of
https://github.com/webmproject/libwebp.git
synced 2025-07-15 21:39:59 +02:00
add colorspace for premultiplied alpha
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
161
src/dec/io.c
161
src/dec/io.c
@ -52,9 +52,7 @@ static int EmitSampledRGB(const VP8Io* const io, WebPDecParams* const p) {
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const uint8_t* y_src = io->y;
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const uint8_t* u_src = io->u;
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const uint8_t* v_src = io->v;
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const WebPSampleLinePairFunc sample =
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io->a ? WebPSamplersKeepAlpha[output->colorspace]
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: WebPSamplers[output->colorspace];
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const WebPSampleLinePairFunc sample = WebPSamplers[output->colorspace];
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const int mb_w = io->mb_w;
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const int last = io->mb_h - 1;
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int j;
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@ -106,9 +104,7 @@ static int EmitFancyRGB(const VP8Io* const io, WebPDecParams* const p) {
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int num_lines_out = io->mb_h; // a priori guess
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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uint8_t* dst = buf->rgba + io->mb_y * buf->stride;
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const WebPUpsampleLinePairFunc upsample =
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io->a ? WebPUpsamplersKeepAlpha[p->output->colorspace]
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: WebPUpsamplers[p->output->colorspace];
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WebPUpsampleLinePairFunc upsample = WebPUpsamplers[p->output->colorspace];
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const uint8_t* cur_y = io->y;
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const uint8_t* cur_u = io->u;
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const uint8_t* cur_v = io->v;
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@ -124,8 +120,6 @@ static int EmitFancyRGB(const VP8Io* const io, WebPDecParams* const p) {
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upsample(NULL, cur_y, cur_u, cur_v, cur_u, cur_v, NULL, dst, mb_w);
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} else {
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// We can finish the left-over line from previous call.
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// Warning! Don't overwrite the alpha values (if any), as they
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// are not lagging one line behind but are already written.
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upsample(p->tmp_y, cur_y, top_u, top_v, cur_u, cur_v,
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dst - buf->stride, dst, mb_w);
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++num_lines_out;
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@ -184,45 +178,73 @@ static int EmitAlphaYUV(const VP8Io* const io, WebPDecParams* const p) {
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}
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static int EmitAlphaRGB(const VP8Io* const io, WebPDecParams* const p) {
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const int mb_w = io->mb_w;
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const int mb_h = io->mb_h;
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int i, j;
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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uint8_t* dst = buf->rgba + io->mb_y * buf->stride +
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(p->output->colorspace == MODE_ARGB ? 0 : 3);
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const uint8_t* alpha = io->a;
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if (alpha) {
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for (j = 0; j < mb_h; ++j) {
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for (i = 0; i < mb_w; ++i) {
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dst[4 * i] = alpha[i];
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if (alpha != NULL) {
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const int mb_w = io->mb_w;
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const int mb_h = io->mb_h;
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int i, j;
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const WEBP_CSP_MODE colorspace = p->output->colorspace;
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const int alpha_first =
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(colorspace == MODE_ARGB || colorspace == MODE_Argb);
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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int start_y = io->mb_y;
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int num_rows = mb_h;
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// We compensate for the 1-line delay of fancy upscaler.
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// This is similar to EmitFancyRGB().
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if (io->fancy_upsampling) {
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if (start_y == 0) {
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// We don't process the last row yet. It'll be done during next call.
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--num_rows;
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} else {
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--start_y;
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// Fortunately, *alpha data is persistent, so we can go back
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// one row and finish alpha blending, now that the fancy upscaler
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// completed the YUV->RGB interpolation.
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alpha -= io->width;
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}
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if (io->crop_top + io->mb_y + mb_h == io->crop_bottom) {
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// If it's the very last call, we process all the remaing rows!
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num_rows = io->crop_bottom - io->crop_top - start_y;
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}
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}
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{
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uint8_t* const base_rgba = buf->rgba + start_y * buf->stride;
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uint8_t* dst = base_rgba + (alpha_first ? 0 : 3);
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for (j = 0; j < num_rows; ++j) {
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for (i = 0; i < mb_w; ++i) dst[4 * i] = alpha[i];
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alpha += io->width;
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dst += buf->stride;
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}
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if (WebPIsPremultipliedMode(colorspace)) {
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WebPApplyAlphaMultiply(base_rgba, alpha_first,
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mb_w, num_rows, buf->stride);
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}
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alpha += io->width;
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dst += buf->stride;
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}
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}
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return 0;
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}
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static WEBP_INLINE uint32_t clip(uint32_t v, uint32_t max_value) {
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return (v > max_value) ? max_value : v;
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}
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static int EmitAlphaRGBA4444(const VP8Io* const io, WebPDecParams* const p) {
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const int mb_w = io->mb_w;
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const int mb_h = io->mb_h;
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int i, j;
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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uint8_t* dst = buf->rgba + io->mb_y * buf->stride + 1;
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const uint8_t* alpha = io->a;
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if (alpha) {
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if (alpha != NULL) {
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const int mb_w = io->mb_w;
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const int mb_h = io->mb_h;
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int i, j;
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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uint8_t* const base_rgba = buf->rgba + io->mb_y * buf->stride;
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uint8_t* alpha_dst = base_rgba + 1;
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for (j = 0; j < mb_h; ++j) {
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for (i = 0; i < mb_w; ++i) {
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// Fill in the alpha value (converted to 4 bits).
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const uint32_t alpha_val = clip((alpha[i] + 8) >> 4, 15);
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dst[2 * i] = (dst[2 * i] & 0xf0) | alpha_val;
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const uint32_t alpha_val = VP8Clip4Bits(alpha[i]);
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alpha_dst[2 * i] = (alpha_dst[2 * i] & 0xf0) | alpha_val;
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}
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alpha += io->width;
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dst += buf->stride;
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alpha_dst += buf->stride;
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}
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if (p->output->colorspace == MODE_rgbA_4444) {
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WebPApplyAlphaMultiply4444(base_rgba, mb_w, mb_h, buf->stride);
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}
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}
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return 0;
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@ -259,13 +281,8 @@ static int EmitRescaledAlphaYUV(const VP8Io* const io, WebPDecParams* const p) {
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return 0;
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}
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static int IsAlphaMode(WEBP_CSP_MODE mode) {
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return (mode == MODE_RGBA || mode == MODE_BGRA || mode == MODE_ARGB ||
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mode == MODE_RGBA_4444 || mode == MODE_YUVA);
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}
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static int InitYUVRescaler(const VP8Io* const io, WebPDecParams* const p) {
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const int has_alpha = IsAlphaMode(p->output->colorspace);
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const int has_alpha = WebPIsAlphaMode(p->output->colorspace);
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const WebPYUVABuffer* const buf = &p->output->u.YUVA;
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const int out_width = io->scaled_width;
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const int out_height = io->scaled_height;
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@ -302,6 +319,7 @@ static int InitYUVRescaler(const VP8Io* const io, WebPDecParams* const p) {
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uv_in_height, uv_out_height,
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work + work_size + uv_work_size);
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p->emit = EmitRescaledYUV;
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if (has_alpha) {
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WebPRescalerInit(&p->scaler_a, io->mb_w, io->mb_h,
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buf->a, out_width, out_height, buf->a_stride, 1,
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@ -364,59 +382,73 @@ static int EmitRescaledRGB(const VP8Io* const io, WebPDecParams* const p) {
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static int ExportAlpha(WebPDecParams* const p, int y_pos) {
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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uint8_t* dst = buf->rgba + (p->last_y + y_pos) * buf->stride +
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(p->output->colorspace == MODE_ARGB ? 0 : 3);
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uint8_t* const base_rgba = buf->rgba + (p->last_y + y_pos) * buf->stride;
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const WEBP_CSP_MODE colorspace = p->output->colorspace;
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const int alpha_first =
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(colorspace == MODE_ARGB || colorspace == MODE_Argb);
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uint8_t* dst = base_rgba + (alpha_first ? 0 : 3);
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int num_lines_out = 0;
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const int is_premult_alpha = WebPIsPremultipliedMode(colorspace);
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const int width = p->scaler_a.dst_width;
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while (WebPRescalerHasPendingOutput(&p->scaler_a)) {
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int i;
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assert(p->last_y + y_pos + num_lines_out < p->output->height);
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WebPRescalerExportRow(&p->scaler_a);
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for (i = 0; i < p->scaler_a.dst_width; ++i) {
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dst[4 * i] = p->scaler_a.dst[i];
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}
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for (i = 0; i < width; ++i) dst[4 * i] = p->scaler_a.dst[i];
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dst += buf->stride;
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++num_lines_out;
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}
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if (is_premult_alpha) {
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WebPApplyAlphaMultiply(base_rgba, alpha_first,
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width, num_lines_out, buf->stride);
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}
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return num_lines_out;
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}
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static int ExportAlphaRGBA4444(WebPDecParams* const p, int y_pos) {
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const WebPRGBABuffer* const buf = &p->output->u.RGBA;
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uint8_t* dst = buf->rgba + (p->last_y + y_pos) * buf->stride + 1;
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uint8_t* base_rgba = buf->rgba + (p->last_y + y_pos) * buf->stride;
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uint8_t* alpha_dst = base_rgba + 1;
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int num_lines_out = 0;
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const WEBP_CSP_MODE colorspace = p->output->colorspace;
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const int width = p->scaler_a.dst_width;
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const int is_premult_alpha = WebPIsPremultipliedMode(colorspace);
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while (WebPRescalerHasPendingOutput(&p->scaler_a)) {
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int i;
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assert(p->last_y + y_pos + num_lines_out < p->output->height);
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WebPRescalerExportRow(&p->scaler_a);
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for (i = 0; i < p->scaler_a.dst_width; ++i) {
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for (i = 0; i < width; ++i) {
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// Fill in the alpha value (converted to 4 bits).
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const uint32_t alpha_val = clip((p->scaler_a.dst[i] + 8) >> 4, 15);
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dst[2 * i] = (dst[2 * i] & 0xf0) | alpha_val;
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const uint32_t alpha_val = VP8Clip4Bits(p->scaler_a.dst[i]);
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alpha_dst[2 * i] = (alpha_dst[2 * i] & 0xf0) | alpha_val;
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}
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dst += buf->stride;
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alpha_dst += buf->stride;
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++num_lines_out;
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}
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if (is_premult_alpha) {
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WebPApplyAlphaMultiply4444(base_rgba, width, num_lines_out, buf->stride);
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}
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return num_lines_out;
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}
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static int EmitRescaledAlphaRGB(const VP8Io* const io, WebPDecParams* const p) {
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if (io->a != NULL) {
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int (* const output_func)(WebPDecParams* const, int) =
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(p->output->colorspace == MODE_RGBA_4444) ? ExportAlphaRGBA4444
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: ExportAlpha;
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WebPRescaler* const scaler = &p->scaler_a;
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int j = 0, pos = 0;
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int j = 0;
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int pos = 0;
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while (j < io->mb_h) {
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j += WebPRescalerImport(scaler, io->mb_h - j,
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io->a + j * io->width, io->width);
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pos += output_func(p, pos);
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pos += p->emit_alpha_row(p, pos);
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}
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}
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return 0;
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}
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static int InitRGBRescaler(const VP8Io* const io, WebPDecParams* const p) {
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const int has_alpha = IsAlphaMode(p->output->colorspace);
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const int has_alpha = WebPIsAlphaMode(p->output->colorspace);
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const int out_width = io->scaled_width;
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const int out_height = io->scaled_height;
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const int uv_in_width = (io->mb_w + 1) >> 1;
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@ -459,6 +491,12 @@ static int InitRGBRescaler(const VP8Io* const io, WebPDecParams* const p) {
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io->mb_w, out_width, io->mb_h, out_height,
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work + 3 * work_size);
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p->emit_alpha = EmitRescaledAlphaRGB;
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if (p->output->colorspace == MODE_RGBA_4444 ||
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p->output->colorspace == MODE_rgbA_4444) {
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p->emit_alpha_row = ExportAlphaRGBA4444;
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} else {
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p->emit_alpha_row = ExportAlpha;
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}
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}
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return 1;
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}
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@ -469,12 +507,13 @@ static int InitRGBRescaler(const VP8Io* const io, WebPDecParams* const p) {
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static int CustomSetup(VP8Io* io) {
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WebPDecParams* const p = (WebPDecParams*)io->opaque;
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const WEBP_CSP_MODE colorspace = p->output->colorspace;
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const int is_rgb = (colorspace < MODE_YUV);
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const int is_alpha = IsAlphaMode(colorspace);
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const int is_rgb = WebPIsRGBMode(colorspace);
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const int is_alpha = WebPIsAlphaMode(colorspace);
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p->memory = NULL;
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p->emit = NULL;
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p->emit_alpha = NULL;
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p->emit_alpha_row = NULL;
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if (!WebPIoInitFromOptions(p->options, io, is_alpha ? MODE_YUV : MODE_YUVA)) {
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return 0;
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}
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@ -505,10 +544,12 @@ static int CustomSetup(VP8Io* io) {
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p->emit = EmitYUV;
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}
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if (is_alpha) { // need transparency output
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if (WebPIsPremultipliedMode(colorspace)) WebPInitPremultiply();
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p->emit_alpha =
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is_rgb ? (colorspace == MODE_RGBA_4444 ? EmitAlphaRGBA4444
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: EmitAlphaRGB)
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: EmitAlphaYUV;
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(colorspace == MODE_RGBA_4444 || colorspace == MODE_rgbA_4444) ?
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EmitAlphaRGBA4444
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: is_rgb ? EmitAlphaRGB
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: EmitAlphaYUV;
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}
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}
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