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Speedup method StoreImageToBitMask by 5%.

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Speedup method StoreImageToBitMask by replacing the code to find histogram
index and Huffman tree codes at every iteration to a more optimal code that
updates these only when the current pixel (to write) crosses the histogram
tile-row boundary.

This change speeds up the StoreImageToBitMask method by 5%.

Change-Id: If01a1ccd7820f9a3a3e5bc449d070defa51be14b
This commit is contained in:
Vikas Arora 2015-02-20 09:45:32 -08:00
parent 602a00f93f
commit ef98750027
1 changed files with 13 additions and 5 deletions
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18
src/enc/vp8l.c
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@ -628,17 +628,25 @@ static WebPEncodingError StoreImageToBitMask(
VP8LBackwardRefs* const refs,
const uint16_t* histogram_symbols,
const HuffmanTreeCode* const huffman_codes) {
const int histo_xsize = histo_bits ? VP8LSubSampleSize(width, histo_bits) : 1;
const int tile_mask = (histo_bits == 0) ? 0 : -(1 << histo_bits);
// x and y trace the position in the image.
int x = 0;
int y = 0;
const int histo_xsize = histo_bits ? VP8LSubSampleSize(width, histo_bits) : 1;
int tile_x = x & tile_mask;
int tile_y = y & tile_mask;
int histogram_ix = histogram_symbols[0];
const HuffmanTreeCode* codes = huffman_codes + 5 * histogram_ix;
VP8LRefsCursor c = VP8LRefsCursorInit(refs);
while (VP8LRefsCursorOk(&c)) {
const PixOrCopy* const v = c.cur_pos;
const int histogram_ix = histogram_symbols[histo_bits ?
(y >> histo_bits) * histo_xsize +
(x >> histo_bits) : 0];
const HuffmanTreeCode* const codes = huffman_codes + 5 * histogram_ix;
if ((tile_x != (x & tile_mask)) || (tile_y != (y & tile_mask))) {
tile_x = x & tile_mask;
tile_y = y & tile_mask;
histogram_ix = histogram_symbols[(y >> histo_bits) * histo_xsize +
(x >> histo_bits)];
codes = huffman_codes + 5 * histogram_ix;
}
if (PixOrCopyIsCacheIdx(v)) {
const int code = PixOrCopyCacheIdx(v);
const int literal_ix = 256 + NUM_LENGTH_CODES + code;