diff options
Diffstat (limited to 'drivers/webp/dec/frame.c')
| -rw-r--r-- | drivers/webp/dec/frame.c | 30 |
1 files changed, 10 insertions, 20 deletions
diff --git a/drivers/webp/dec/frame.c b/drivers/webp/dec/frame.c index b882133eab..22d291d2cd 100644 --- a/drivers/webp/dec/frame.c +++ b/drivers/webp/dec/frame.c @@ -316,6 +316,9 @@ static void PrecomputeFilterStrengths(VP8Decoder* const dec) { //------------------------------------------------------------------------------ // Dithering +// minimal amp that will provide a non-zero dithering effect +#define MIN_DITHER_AMP 4 + #define DITHER_AMP_TAB_SIZE 12 static const int kQuantToDitherAmp[DITHER_AMP_TAB_SIZE] = { // roughly, it's dqm->uv_mat_[1] @@ -356,27 +359,14 @@ void VP8InitDithering(const WebPDecoderOptions* const options, } } -// minimal amp that will provide a non-zero dithering effect -#define MIN_DITHER_AMP 4 -#define DITHER_DESCALE 4 -#define DITHER_DESCALE_ROUNDER (1 << (DITHER_DESCALE - 1)) -#define DITHER_AMP_BITS 8 -#define DITHER_AMP_CENTER (1 << DITHER_AMP_BITS) - +// Convert to range: [-2,2] for dither=50, [-4,4] for dither=100 static void Dither8x8(VP8Random* const rg, uint8_t* dst, int bps, int amp) { - int i, j; - for (j = 0; j < 8; ++j) { - for (i = 0; i < 8; ++i) { - // TODO: could be made faster with SSE2 - const int bits = - VP8RandomBits2(rg, DITHER_AMP_BITS + 1, amp) - DITHER_AMP_CENTER; - // Convert to range: [-2,2] for dither=50, [-4,4] for dither=100 - const int delta = (bits + DITHER_DESCALE_ROUNDER) >> DITHER_DESCALE; - const int v = (int)dst[i] + delta; - dst[i] = (v < 0) ? 0 : (v > 255) ? 255u : (uint8_t)v; - } - dst += bps; + uint8_t dither[64]; + int i; + for (i = 0; i < 8 * 8; ++i) { + dither[i] = VP8RandomBits2(rg, VP8_DITHER_AMP_BITS + 1, amp); } + VP8DitherCombine8x8(dither, dst, bps); } static void DitherRow(VP8Decoder* const dec) { @@ -462,7 +452,7 @@ static int FinishRow(VP8Decoder* const dec, VP8Io* const io) { if (dec->alpha_data_ != NULL && y_start < y_end) { // TODO(skal): testing presence of alpha with dec->alpha_data_ is not a // good idea. - io->a = VP8DecompressAlphaRows(dec, y_start, y_end - y_start); + io->a = VP8DecompressAlphaRows(dec, io, y_start, y_end - y_start); if (io->a == NULL) { return VP8SetError(dec, VP8_STATUS_BITSTREAM_ERROR, "Could not decode alpha data."); |