diff options
| -rw-r--r-- | raster/imagescale.c | 78 |
1 files changed, 74 insertions, 4 deletions
diff --git a/raster/imagescale.c b/raster/imagescale.c index e1c61865..bbe20565 100644 --- a/raster/imagescale.c +++ b/raster/imagescale.c @@ -36,24 +36,94 @@ static inline void srown(byte * restrict src, byte * restrict dst, int w, int de dst[k] = sum[k] / left; } +// special-case common 1-5 components - the compiler optimizes this +static inline void srowc(byte * restrict src, byte * restrict dst, int w, int denom, int n) +{ + int invdenom = (1<<16) / denom; + int x, left; + unsigned sum1 = 0; + unsigned sum2 = 0; + unsigned sum3 = 0; + unsigned sum4 = 0; + unsigned sum5 = 0; + + assert(n <= 5); + + left = 0; + + for (x = 0; x < w; x++) + { + sum1 += src[x * n + 0]; + // the compiler eliminates these if-tests + if (n >= 2) + sum2 += src[x * n + 1]; + if (n >= 3) + sum3 += src[x * n + 2]; + if (n >= 4) + sum4 += src[x * n + 3]; + if (n >= 5) + sum5 += src[x * n + 4]; + + if (++left == denom) + { + left = 0; + + dst[0] = (sum1 * invdenom) >> 16; + sum1 = 0; + if (n >= 2) { + dst[1] = (sum2 * invdenom) >> 16; + sum2 = 0; + } + if (n >= 3) { + dst[2] = (sum3 * invdenom) >> 16; + sum3 = 0; + } + if (n >= 4) { + dst[3] = (sum4 * invdenom) >> 16; + sum4 = 0; + } + if (n >= 5) { + dst[4] = (sum5 * invdenom) >> 16; + sum5 = 0; + } + + + dst += n; + } + } + + /* left overs */ + if (left) { + dst[0] = sum1 / left; + if (n >=2) + dst[1] = sum2 / left; + if (n >=3) + dst[2] = sum3 / left; + if (n >=4) + dst[3] = sum4 / left; + if (n >=5) + dst[4] = sum5 / left; + } +} + static void srow1(byte *src, byte *dst, int w, int denom) { - srown(src, dst, w, denom, 1); + srowc(src, dst, w, denom, 1); } static void srow2(byte *src, byte *dst, int w, int denom) { - srown(src, dst, w, denom, 2); + srowc(src, dst, w, denom, 2); } static void srow4(byte *src, byte *dst, int w, int denom) { - srown(src, dst, w, denom, 4); + srowc(src, dst, w, denom, 4); } static void srow5(byte *src, byte *dst, int w, int denom) { - srown(src, dst, w, denom, 5); + srowc(src, dst, w, denom, 5); } static inline void scoln(byte * restrict src, byte * restrict dst, int w, int denom, int n) |