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Do basic gamma correction when rendering text.

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git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/back/trunk@14357 72102866-910b-0410-8b05-ffd578937521
This commit is contained in:
Alexander Malmberg 2002-08-27 22:36:20 +00:00
parent e4c7c1a263
commit 5e03fc72e9
2 changed files with 51 additions and 0 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2002-08-28 00:34 Alexander Malmberg <alexander@malmberg.org>
* Source/art/blit.m: Do basic gamma correction when rendering
text.
2002-08-27 12:10 Alexander Malmberg <alexander@malmberg.org>
* Source/art/: Fix copyright notices.

46
Source/art/blit.m
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@ -26,6 +26,7 @@ This file includes itself. Many times. You have been warned.
#ifndef FORMAT_INSTANCE
#include <math.h>
#include <string.h>
#include "x11/XGServer.h"
@ -53,6 +54,14 @@ TODO: more cpp magic to reduce the amount of code?
*/
/*
First attempt at gamma correction. Only used in text rendering (blit_*),
but that's where it's needed the most. The gamma adjustment is a large
hack, but the results are good.
*/
static unsigned char gamma_table[256],inv_gamma_table[256];
#define NPRE(r, pre) pre##_##r
@ -88,10 +97,17 @@ static void MPRE(blit_alpha_opaque) (unsigned char *adst,
BLEND_INC(dst)
continue;
}
BLEND_READ(dst, nr, ng, nb)
nr = inv_gamma_table[nr];
ng = inv_gamma_table[ng];
nb = inv_gamma_table[nb];
nr = (r * a + nr * (255 - a) + 0xff) >> 8;
ng = (g * a + ng * (255 - a) + 0xff) >> 8;
nb = (b * a + nb * (255 - a) + 0xff) >> 8;
nr = gamma_table[nr];
ng = gamma_table[ng];
nb = gamma_table[nb];
BLEND_WRITE(dst, nr, ng, nb)
BLEND_INC(dst)
}
@ -223,6 +239,10 @@ static void MPRE(blit_subpixel) (unsigned char *adst, const unsigned char *asrc,
BLEND_READ(dst, nr, ng, nb)
nr = inv_gamma_table[nr];
ng = inv_gamma_table[ng];
nb = inv_gamma_table[nb];
ar *= alpha;
ag *= alpha;
ab *= alpha;
@ -230,6 +250,11 @@ static void MPRE(blit_subpixel) (unsigned char *adst, const unsigned char *asrc,
nr = (r * ar + nr * (65280 - ar) + 0xff00) >> 16;
ng = (g * ag + ng * (65280 - ag) + 0xff00) >> 16;
nb = (b * ab + nb * (65280 - ab) + 0xff00) >> 16;
nr = gamma_table[nr];
ng = gamma_table[ng];
nb = gamma_table[nb];
BLEND_WRITE(dst, nr, ng, nb)
BLEND_INC(dst)
}
@ -1562,6 +1587,9 @@ static int byte_ofs_of_mask(unsigned int m)
return -1;
}
#include <Foundation/NSUserDefaults.h>
void artcontext_setup_draw_info(draw_info_t *di,
unsigned int red_mask, unsigned int green_mask, unsigned int blue_mask,
int bpp)
@ -1619,6 +1647,24 @@ void artcontext_setup_draw_info(draw_info_t *di,
@"and send me a patch.)");
exit(1);
}
{
float gamma = [[NSUserDefaults standardUserDefaults]
floatForKey: @"back-art-text-gamma"];
int i;
if (!gamma)
gamma = 1.4;
NSLog(@"gamma=%g",gamma);
gamma = 1.0 / gamma;
for (i = 0; i < 256; i++)
{
gamma_table[i] = pow(i / 255.0, gamma) * 255 + .5;
inv_gamma_table[i] = pow(i / 255.0, 1.0 / gamma) * 255 + .5;
}
}
}
#endif