The Tor Browser / file diff

     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/gfx/cairo/libpixman/src/pixman-dither.h	Wed Dec 31 06:09:35 2014 +0100
     1.3 @@ -0,0 +1,51 @@
     1.4 +#define R16_BITS     5
     1.5 +#define G16_BITS     6
     1.6 +#define B16_BITS     5
     1.7 +
     1.8 +#define R16_SHIFT    (B16_BITS + G16_BITS)
     1.9 +#define G16_SHIFT    (B16_BITS)
    1.10 +#define B16_SHIFT    0
    1.11 +
    1.12 +#define MASK 0xff
    1.13 +#define ONE_HALF 0x80
    1.14 +
    1.15 +#define A_SHIFT 8 * 3
    1.16 +#define R_SHIFT 8 * 2
    1.17 +#define G_SHIFT 8
    1.18 +#define A_MASK 0xff000000
    1.19 +#define R_MASK 0xff0000
    1.20 +#define G_MASK 0xff00
    1.21 +
    1.22 +#define RB_MASK 0xff00ff
    1.23 +#define AG_MASK 0xff00ff00
    1.24 +#define RB_ONE_HALF 0x800080
    1.25 +#define RB_MASK_PLUS_ONE 0x10000100
    1.26 +
    1.27 +#define ALPHA_8(x) ((x) >> A_SHIFT)
    1.28 +#define RED_8(x) (((x) >> R_SHIFT) & MASK)
    1.29 +#define GREEN_8(x) (((x) >> G_SHIFT) & MASK)
    1.30 +#define BLUE_8(x) ((x) & MASK)
    1.31 +
    1.32 +// This uses the same dithering technique that Skia does.
    1.33 +// It is essentially preturbing the lower bit based on the
    1.34 +// high bit
    1.35 +static inline uint16_t dither_32_to_16(uint32_t c)
    1.36 +{
    1.37 +    uint8_t b = BLUE_8(c);
    1.38 +    uint8_t g = GREEN_8(c);
    1.39 +    uint8_t r = RED_8(c);
    1.40 +    r = ((r << 1) - ((r >> (8 - R16_BITS) << (8 - R16_BITS)) | (r >> R16_BITS))) >> (8 - R16_BITS);
    1.41 +    g = ((g << 1) - ((g >> (8 - G16_BITS) << (8 - G16_BITS)) | (g >> G16_BITS))) >> (8 - G16_BITS);
    1.42 +    b = ((b << 1) - ((b >> (8 - B16_BITS) << (8 - B16_BITS)) | (b >> B16_BITS))) >> (8 - B16_BITS);
    1.43 +    return ((r << R16_SHIFT) | (g << G16_SHIFT) | (b << B16_SHIFT));
    1.44 +}
    1.45 +
    1.46 +static inline uint16_t dither_8888_to_0565(uint32_t color, pixman_bool_t toggle)
    1.47 +{
    1.48 +    // alternate between a preturbed truncation and a regular truncation
    1.49 +    if (toggle) {
    1.50 +	return dither_32_to_16(color);
    1.51 +    } else {
    1.52 +	return convert_8888_to_0565(color);
    1.53 +    }
    1.54 +}