gfx/cairo/libpixman/src/pixman-dither.h@6474c204b198
gfx/cairo/libpixman/src/pixman-dither.h
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
1 #define R16_BITS 5
2 #define G16_BITS 6
3 #define B16_BITS 5
5 #define R16_SHIFT (B16_BITS + G16_BITS)
6 #define G16_SHIFT (B16_BITS)
7 #define B16_SHIFT 0
9 #define MASK 0xff
10 #define ONE_HALF 0x80
12 #define A_SHIFT 8 * 3
13 #define R_SHIFT 8 * 2
14 #define G_SHIFT 8
15 #define A_MASK 0xff000000
16 #define R_MASK 0xff0000
17 #define G_MASK 0xff00
19 #define RB_MASK 0xff00ff
20 #define AG_MASK 0xff00ff00
21 #define RB_ONE_HALF 0x800080
22 #define RB_MASK_PLUS_ONE 0x10000100
24 #define ALPHA_8(x) ((x) >> A_SHIFT)
25 #define RED_8(x) (((x) >> R_SHIFT) & MASK)
26 #define GREEN_8(x) (((x) >> G_SHIFT) & MASK)
27 #define BLUE_8(x) ((x) & MASK)
29 // This uses the same dithering technique that Skia does.
30 // It is essentially preturbing the lower bit based on the
31 // high bit
32 static inline uint16_t dither_32_to_16(uint32_t c)
33 {
34 uint8_t b = BLUE_8(c);
35 uint8_t g = GREEN_8(c);
36 uint8_t r = RED_8(c);
37 r = ((r << 1) - ((r >> (8 - R16_BITS) << (8 - R16_BITS)) | (r >> R16_BITS))) >> (8 - R16_BITS);
38 g = ((g << 1) - ((g >> (8 - G16_BITS) << (8 - G16_BITS)) | (g >> G16_BITS))) >> (8 - G16_BITS);
39 b = ((b << 1) - ((b >> (8 - B16_BITS) << (8 - B16_BITS)) | (b >> B16_BITS))) >> (8 - B16_BITS);
40 return ((r << R16_SHIFT) | (g << G16_SHIFT) | (b << B16_SHIFT));
41 }
43 static inline uint16_t dither_8888_to_0565(uint32_t color, pixman_bool_t toggle)
44 {
45 // alternate between a preturbed truncation and a regular truncation
46 if (toggle) {
47 return dither_32_to_16(color);
48 } else {
49 return convert_8888_to_0565(color);
50 }
51 }
