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https://github.com/webmproject/libwebp.git
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Harmonize the alpha-filter predictions at boundary
often reduces compressed size by ~10's of bytes + refactored / sped-up the prediction code (gradient: ~30% faster) Change-Id: I26bd983655dad4f85d5c5ddc20a1980f384c4dd6
This commit is contained in:
Pascal Massimino
parent
3a9895340f
commit
57cab7b891
@ -30,140 +30,127 @@ extern "C" {
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assert(bpp > 0); \
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assert(stride >= width * bpp);
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static WEBP_INLINE void PredictLine(const uint8_t* src, const uint8_t* pred,
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uint8_t* dst, int length, int inverse) {
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int i;
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if (inverse) {
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for (i = 0; i < length; ++i) dst[i] = src[i] + pred[i];
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} else {
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for (i = 0; i < length; ++i) dst[i] = src[i] - pred[i];
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}
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}
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//------------------------------------------------------------------------------
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// Horizontal filter.
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static void HorizontalFilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* filtered_data) {
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static WEBP_INLINE void DoHorizontalFilter(const uint8_t* in,
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int width, int height, int bpp, int stride, int inverse, uint8_t* out) {
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int h;
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SANITY_CHECK(data, filtered_data);
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const uint8_t* preds = (inverse ? out : in);
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SANITY_CHECK(in, out);
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// Filter line-by-line.
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for (h = 0; h < height; ++h) {
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int w;
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const uint8_t* const scan_line = data + h * stride;
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uint8_t* const out = filtered_data + h * stride;
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memcpy((void*)out, (const void*)scan_line, bpp);
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for (w = bpp; w < width * bpp; ++w) {
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out[w] = scan_line[w] - scan_line[w - bpp];
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// Leftmost pixel is predicted from above (except for topmost scanline).
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if (h == 0) {
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memcpy((void*)out, (const void*)in, bpp);
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} else {
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PredictLine(in, preds - stride, out, bpp, inverse);
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}
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PredictLine(in + bpp, preds, out + bpp, bpp * (width - 1), inverse);
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preds += stride;
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in += stride;
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out += stride;
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}
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}
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static void HorizontalFilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* filtered_data) {
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DoHorizontalFilter(data, width, height, bpp, stride, 0, filtered_data);
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}
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static void HorizontalUnfilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* recon_data) {
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int h;
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SANITY_CHECK(data, recon_data);
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// Unfilter line-by-line.
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for (h = 0; h < height; ++h) {
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int w;
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const uint8_t* const scan_line = data + h * stride;
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uint8_t* const out = recon_data + h * stride;
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memcpy((void*)out, (const void*)scan_line, bpp);
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for (w = bpp; w < width * bpp; ++w) {
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out[w] = scan_line[w] + out[w - bpp];
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}
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}
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DoHorizontalFilter(data, width, height, bpp, stride, 1, recon_data);
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}
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//------------------------------------------------------------------------------
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// Vertical filter.
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static void VerticalFilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* filtered_data) {
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static WEBP_INLINE void DoVerticalFilter(const uint8_t* in,
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int width, int height, int bpp, int stride, int inverse, uint8_t* out) {
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int h;
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SANITY_CHECK(data, filtered_data);
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const uint8_t* preds = (inverse ? out : in);
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SANITY_CHECK(in, out);
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// Copy top scan-line as it is.
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memcpy((void*)filtered_data, (const void*)data, width * bpp);
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// Very first top-left pixel is copied.
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memcpy((void*)out, (const void*)in, bpp);
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// Rest of top scan-line is left-predicted.
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PredictLine(in + bpp, preds, out + bpp, bpp * (width - 1), inverse);
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// Filter line-by-line.
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for (h = 1; h < height; ++h) {
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int w;
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const uint8_t* const scan_line = data + h * stride;
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uint8_t* const out = filtered_data + h * stride;
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const uint8_t* const prev_line = scan_line - stride;
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for (w = 0; w < width * bpp; ++w) {
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out[w] = scan_line[w] - prev_line[w];
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}
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in += stride;
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out += stride;
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PredictLine(in, preds, out, bpp * width, inverse);
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preds += stride;
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}
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}
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static void VerticalFilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* filtered_data) {
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DoVerticalFilter(data, width, height, bpp, stride, 0, filtered_data);
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}
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static void VerticalUnfilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* recon_data) {
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int h;
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SANITY_CHECK(data, recon_data);
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// Copy top scan-line as it is.
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memcpy((void*)recon_data, (const void*)data, width * bpp);
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// Unfilter line-by-line.
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for (h = 1; h < height; ++h) {
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int w;
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const uint8_t* const scan_line = data + h * stride;
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uint8_t* const out = recon_data + h * stride;
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const uint8_t* const out_prev_line = out - stride;
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for (w = 0; w < width * bpp; ++w) {
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out[w] = scan_line[w] + out_prev_line[w];
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}
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}
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DoVerticalFilter(data, width, height, bpp, stride, 1, recon_data);
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}
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//------------------------------------------------------------------------------
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// Gradient filter.
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static WEBP_INLINE uint8_t GradientPredictor(uint8_t a, uint8_t b, uint8_t c) {
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static WEBP_INLINE int GradientPredictor(uint8_t a, uint8_t b, uint8_t c) {
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const int g = a + b - c;
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return (g < 0) ? 0 : (g > 255) ? 255 : (uint8_t)g;
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return (g < 0) ? 0 : (g > 255) ? 255 : g;
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}
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static void GradientFilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* filtered_data) {
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static WEBP_INLINE
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void DoGradientFilter(const uint8_t* in, int width, int height,
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int bpp, int stride, int inverse, uint8_t* out) {
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const uint8_t* preds = (inverse ? out : in);
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int h;
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SANITY_CHECK(data, filtered_data);
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SANITY_CHECK(in, out);
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// Copy top scan-line as it is.
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memcpy((void*)filtered_data, (const void*)data, width * bpp);
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// left prediction for top scan-line
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memcpy((void*)out, (const void*)in, bpp);
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PredictLine(in + bpp, preds, out + bpp, bpp * (width - 1), inverse);
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// Filter line-by-line.
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for (h = 1; h < height; ++h) {
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int w;
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const uint8_t* const scan_line = data + h * stride;
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uint8_t* const out = filtered_data + h * stride;
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const uint8_t* const prev_line = scan_line - stride;
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memcpy((void*)out, (const void*)scan_line, bpp);
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preds += stride;
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in += stride;
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out += stride;
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// leftmost pixel: predict from above.
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PredictLine(in, preds - stride, out, bpp, inverse);
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for (w = bpp; w < width * bpp; ++w) {
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out[w] = scan_line[w] - GradientPredictor(scan_line[w - bpp],
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prev_line[w],
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prev_line[w - bpp]);
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const int pred = GradientPredictor(preds[w - bpp],
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preds[w - stride],
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preds[w - stride - bpp]);
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out[w] = in[w] + (inverse ? pred : -pred);
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}
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}
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}
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static void GradientFilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* filtered_data) {
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DoGradientFilter(data, width, height, bpp, stride, 0, filtered_data);
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}
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static void GradientUnfilter(const uint8_t* data, int width, int height,
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int bpp, int stride, uint8_t* recon_data) {
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int h;
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SANITY_CHECK(data, recon_data);
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// Copy top scan-line as it is.
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memcpy((void*)recon_data, (const void*)data, width * bpp);
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// Unfilter line-by-line.
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for (h = 1; h < height; ++h) {
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int w;
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const uint8_t* const scan_line = data + h * stride;
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uint8_t* const out = recon_data + h * stride;
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const uint8_t* const out_prev_line = out - stride;
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memcpy((void*)out, (const void*)scan_line, bpp);
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for (w = bpp; w < width * bpp; ++w) {
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out[w] = scan_line[w] + GradientPredictor(out[w - bpp],
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out_prev_line[w],
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out_prev_line[w - bpp]);
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}
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}
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DoGradientFilter(data, width, height, bpp, stride, 1, recon_data);
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}
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#undef SANITY_CHECK
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