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/***************************************************************************
* Copyright (C) 2016 PCSX4ALL Team *
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program; if not, write to the *
* Free Software Foundation, Inc., *
* 51 Franklin Street, Fifth Floor, Boston, MA 02111-1307 USA. *
***************************************************************************/
#ifndef _OP_DITHER_H_
#define _OP_DITHER_H_
static void SetupDitheringConstants()
{
// Initialize Dithering Constants
// The screen is divided into 8x8 chunks and sub-unitary noise is applied
// using the following matrix. This ensures that data lost in color
// quantization will be added back to the image 'by chance' in predictable
// patterns that are naturally 'smoothed' by your sight when viewed from a
// certain distance.
//
// http://caca.zoy.org/study/index.html
//
// Shading colors are encoded in 4.5, and then are quantitized to 5.0,
// DitherMatrix constants reflect that.
static const u8 DitherMatrix[] = {
0, 32, 8, 40, 2, 34, 10, 42,
48, 16, 56, 24, 50, 18, 58, 26,
12, 44, 4, 36, 14, 46, 6, 38,
60, 28, 52, 20, 62, 30, 54, 22,
3, 35, 11, 43, 1, 33, 9, 41,
51, 19, 59, 27, 49, 17, 57, 25,
15, 47, 7, 39, 13, 45, 5, 37,
63, 31, 55, 23, 61, 29, 53, 21
};
int i, j;
for (i = 0; i < 8; i++)
{
for (j = 0; j < 8; j++)
{
u16 offset = (i << 3) | j;
u32 component = ((DitherMatrix[offset] + 1) << 4) / 65; //[5.5] -> [5]
// XXX - senquack - hack Dec 2016
// Until JohnnyF gets the time to work further on dithering,
// force lower bit of component to 0. This fixes grid pattern
// affecting quality of dithered image, as well as loss of
// detail in dark areas. With lower bit unset like this, existing
// 27-bit accuracy of dithering math is unneeded, could be 24-bit.
// Is 8x8 matrix overkill as a result, can we use 4x4?
component &= ~1;
gpu_unai.DitherMatrix[offset] = (component)
| (component << 10)
| (component << 20);
}
}
}
////////////////////////////////////////////////////////////////////////////////
// Convert padded u32 5.4:5.4:5.4 bgr fixed-pt triplet to final bgr555 color,
// applying dithering if specified by template parameter.
//
// INPUT:
// 'uSrc24' input: 000bbbbbXXXX0gggggXXXX0rrrrrXXXX
// ^ bit 31
// 'pDst' is a pointer to destination framebuffer pixel, used
// to determine which DitherMatrix[] entry to apply.
// RETURNS:
// u16 output: 0bbbbbgggggrrrrr
// ^ bit 16
// Where 'X' are fixed-pt bits, '0' is zero-padding, and '-' is don't care
////////////////////////////////////////////////////////////////////////////////
template <int DITHER>
GPU_INLINE u16 gpuColorQuantization24(u32 uSrc24, const u16 *pDst)
{
if (DITHER)
{
u16 fbpos = (u32)(pDst - gpu_unai.vram);
u16 offset = ((fbpos & (0x7 << 10)) >> 7) | (fbpos & 0x7);
//clean overflow flags and add
uSrc24 = (uSrc24 & 0x1FF7FDFF) + gpu_unai.DitherMatrix[offset];
if (uSrc24 & (1<< 9)) uSrc24 |= (0x1FF );
if (uSrc24 & (1<<19)) uSrc24 |= (0x1FF<<10);
if (uSrc24 & (1<<29)) uSrc24 |= (0x1FF<<20);
}
return ((uSrc24>> 4) & (0x1F ))
| ((uSrc24>> 9) & (0x1F<<5 ))
| ((uSrc24>>14) & (0x1F<<10));
}
#endif //_OP_DITHER_H_
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