1 /***************************************************************************
2 * Copyright (C) 2016 PCSX4ALL Team *
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7 * (at your option) any later version. *
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12 * GNU General Public License for more details. *
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16 * Free Software Foundation, Inc., *
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02111-1307 USA. *
18 ***************************************************************************/
23 static void SetupDitheringConstants()
25 // Initialize Dithering Constants
26 // The screen is divided into 8x8 chunks and sub-unitary noise is applied
27 // using the following matrix. This ensures that data lost in color
28 // quantization will be added back to the image 'by chance' in predictable
29 // patterns that are naturally 'smoothed' by your sight when viewed from a
32 // http://caca.zoy.org/study/index.html
34 // Shading colors are encoded in 4.5, and then are quantitized to 5.0,
35 // DitherMatrix constants reflect that.
37 static const u8 DitherMatrix[] = {
38 0, 32, 8, 40, 2, 34, 10, 42,
39 48, 16, 56, 24, 50, 18, 58, 26,
40 12, 44, 4, 36, 14, 46, 6, 38,
41 60, 28, 52, 20, 62, 30, 54, 22,
42 3, 35, 11, 43, 1, 33, 9, 41,
43 51, 19, 59, 27, 49, 17, 57, 25,
44 15, 47, 7, 39, 13, 45, 5, 37,
45 63, 31, 55, 23, 61, 29, 53, 21
49 for (i = 0; i < 8; i++)
51 for (j = 0; j < 8; j++)
53 u16 offset = (i << 3) | j;
55 u32 component = ((DitherMatrix[offset] + 1) << 4) / 65; //[5.5] -> [5]
57 // XXX - senquack - hack Dec 2016
58 // Until JohnnyF gets the time to work further on dithering,
59 // force lower bit of component to 0. This fixes grid pattern
60 // affecting quality of dithered image, as well as loss of
61 // detail in dark areas. With lower bit unset like this, existing
62 // 27-bit accuracy of dithering math is unneeded, could be 24-bit.
63 // Is 8x8 matrix overkill as a result, can we use 4x4?
66 gpu_unai.DitherMatrix[offset] = (component)
73 ////////////////////////////////////////////////////////////////////////////////
74 // Convert padded u32 5.4:5.4:5.4 bgr fixed-pt triplet to final bgr555 color,
75 // applying dithering if specified by template parameter.
78 // 'uSrc24' input: 000bbbbbXXXX0gggggXXXX0rrrrrXXXX
80 // 'pDst' is a pointer to destination framebuffer pixel, used
81 // to determine which DitherMatrix[] entry to apply.
83 // u16 output: 0bbbbbgggggrrrrr
85 // Where 'X' are fixed-pt bits, '0' is zero-padding, and '-' is don't care
86 ////////////////////////////////////////////////////////////////////////////////
88 GPU_INLINE u16 gpuColorQuantization24(u32 uSrc24, const u16 *pDst)
92 u16 fbpos = (u32)(pDst - gpu_unai.vram);
93 u16 offset = ((fbpos & (0x7 << 10)) >> 7) | (fbpos & 0x7);
95 //clean overflow flags and add
96 uSrc24 = (uSrc24 & 0x1FF7FDFF) + gpu_unai.DitherMatrix[offset];
98 if (uSrc24 & (1<< 9)) uSrc24 |= (0x1FF );
99 if (uSrc24 & (1<<19)) uSrc24 |= (0x1FF<<10);
100 if (uSrc24 & (1<<29)) uSrc24 |= (0x1FF<<20);
103 return ((uSrc24>> 4) & (0x1F ))
104 | ((uSrc24>> 9) & (0x1F<<5 ))
105 | ((uSrc24>>14) & (0x1F<<10));
108 #endif //_OP_DITHER_H_