diff options
| -rw-r--r-- | src/mesa/drivers/dri/swrast/swrast_span.c | 40 |
1 files changed, 34 insertions, 6 deletions
diff --git a/src/mesa/drivers/dri/swrast/swrast_span.c b/src/mesa/drivers/dri/swrast/swrast_span.c index 4613a121131..35b9ddffe67 100644 --- a/src/mesa/drivers/dri/swrast/swrast_span.c +++ b/src/mesa/drivers/dri/swrast/swrast_span.c @@ -32,6 +32,32 @@ #define YFLIP(_xrb, Y) ((_xrb)->Base.Height - (Y) - 1) /* + * Dithering support takes the "computation" extreme in the "computation vs. + * storage" trade-off. This approach is very simple to implement and any + * computational overhead should be acceptable. XMesa uses table lookups for + * around 8KB of storage overhead per visual. + */ +#define DITHER 1 + +static const GLubyte kernel[16] = { + 0*16, 8*16, 2*16, 10*16, + 12*16, 4*16, 14*16, 6*16, + 3*16, 11*16, 1*16, 9*16, + 15*16, 7*16, 13*16, 5*16, +}; + +#if DITHER +#define DITHER_COMP(X, Y) kernel[((X) & 0x3) | (((Y) & 0x3) << 2)] + +#define DITHER_CLAMP(X) (((X) < CHAN_MAX) ? (X) : CHAN_MAX) +#else +#define DITHER_COMP(X, Y) 0 + +#define DITHER_CLAMP(X) (X) +#endif + + +/* * Pixel macros shared across front/back buffer span functions. */ @@ -56,10 +82,11 @@ /* 16-bit BGR */ #define STORE_PIXEL_R5G6B5(DST, X, Y, VALUE) \ do { \ + int d = DITHER_COMP(X, Y) >> 6; \ GLushort *p = (GLushort *)DST; \ - *p = ( (((VALUE[RCOMP]) & 0xf8) << 8) | \ - (((VALUE[GCOMP]) & 0xfc) << 3) | \ - (((VALUE[BCOMP]) & 0xf8) >> 3) ); \ + *p = ( ((DITHER_CLAMP((VALUE[RCOMP]) + d) & 0xf8) << 8) | \ + ((DITHER_CLAMP((VALUE[GCOMP]) + d) & 0xfc) << 3) | \ + ((DITHER_CLAMP((VALUE[BCOMP]) + d) & 0xf8) >> 3) ); \ } while(0) #define FETCH_PIXEL_R5G6B5(DST, SRC) \ do { \ @@ -74,10 +101,11 @@ /* 8-bit BGR */ #define STORE_PIXEL_R3G3B2(DST, X, Y, VALUE) \ do { \ + int d = DITHER_COMP(X, Y) >> 3; \ GLubyte *p = (GLubyte *)DST; \ - *p = ( (((VALUE[RCOMP]) & 0xe0) >> 5) | \ - (((VALUE[GCOMP]) & 0xe0) >> 2) | \ - (((VALUE[BCOMP]) & 0xc0) >> 0) ); \ + *p = ( ((DITHER_CLAMP((VALUE[RCOMP]) + d) & 0xe0) >> 5) | \ + ((DITHER_CLAMP((VALUE[GCOMP]) + d) & 0xe0) >> 2) | \ + ((DITHER_CLAMP((VALUE[BCOMP]) + d) & 0xc0) >> 0) ); \ } while(0) #define FETCH_PIXEL_R3G3B2(DST, SRC) \ do { \ |