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#include "config.h"
#include "tty.h"
#include "export.h"
#define R(x) ((uint8_t)((x)>>16))
#define G(x) ((uint8_t)((x)>> 8))
#define B(x) ((uint8_t) (x) )
static uint32_t col256_to_rgb(uint32_t i)
{
i &= 0xff;
// Standard colours.
if (i < 16)
{
if (i == 3)
return 0xaa5500; // real CGA/VGA special-cases brown
int c = (i&1 ? 0xaa0000 : 0x000000)
| (i&2 ? 0x00aa00 : 0x000000)
| (i&4 ? 0x0000aa : 0x000000);
return (i >= 8) ? c + 0x555555 : c;
}
// 6x6x6 colour cube.
else if (i < 232)
{
i -= 16;
int r = i / 36, g = i / 6 % 6, b = i % 6;
return (r ? r * 0x280000 + 0x370000 : 0)
| (g ? g * 0x002800 + 0x003700 : 0)
| (b ? b * 0x000028 + 0x000037 : 0);
}
// Grayscale ramp.
else // i < 256
return (i * 10 - 2312) * 0x010101;
}
static int sqrd(unsigned char a, unsigned char b)
{
int _ = ((int)a) - ((int)b);
return (_>=0)?_:-_;;
}
#if 0
// brightness formula
static uint32_t rgb_diff(uint32_t x, uint32_t y)
{
return 2*sqrd(R(x), R(y))
+ 3*sqrd(G(x), G(y))
+ 1*sqrd(B(x), B(y));
}
#else
// Riermersma's formula
static uint32_t rgb_diff(uint32_t x, uint32_t y)
{
int rm = (R(x)+R(y))/2;
return 2*sqrd(R(x), R(y))
+ 4*sqrd(G(x), G(y))
+ 3*sqrd(B(x), B(y))
+ rm*(sqrd(R(x), R(y))-sqrd(B(x), B(y)))/256;
}
#endif
static uint32_t rgb_to_16(uint32_t c)
{
uint8_t max = R(c);
if (max < G(c))
max = G(c);
if (max < B(c))
max = B(c);
uint8_t hue = 0;
if (R(c) > max/2+32)
hue|=1;
if (G(c) > max/2+32)
hue|=2;
if (B(c) > max/2+32)
hue|=4;
if (hue == 7 && max <= 0x70)
return 8;
return (max > 0xc0) ? hue|8 : hue;
}
static uint32_t m6(uint32_t x)
{
x = (x+5)/40;
return x? x-1 : 0;
}
static uint32_t rgb_to_color_cube(uint32_t c)
{
return 16 + m6(R(c))*36 + m6(G(c))*6 + m6(B(c));
}
static uint32_t rgb_to_grayscale_gradient(uint32_t c)
{
int x = 232 + (R(c)*2 + G(c)*3 + B(c)) / 60;
return (x > 255)? 255 : x;
}
static uint32_t rgb_to_256(uint32_t c)
{
uint32_t c1 = rgb_to_16(c);
uint32_t bd = rgb_diff(c, col256_to_rgb(c1));
uint32_t res = c1;
uint32_t c2 = rgb_to_color_cube(c);
uint32_t d = rgb_diff(c, col256_to_rgb(c2));
if (d < bd)
bd = d, res = c2;
uint32_t c3 = rgb_to_grayscale_gradient(c);
d = rgb_diff(c, col256_to_rgb(c3));
if (d < bd)
res = c3;
return res;
}
export uint32_t tty_color_convert(uint32_t c, uint32_t to)
{
if (!to)
return 0;
uint32_t from = (c&VT100_ATTR_COLOR_TYPE)>>24;
if (to > 3)
to>>=24;
if (from == to)
return c;
if (from==1 && to==2)
return c;
if (from==1 || from==2)
c = col256_to_rgb(c);
switch (to)
{
case 1:
return rgb_to_16(c);
case 2:
return rgb_to_256(c);
case 3:
return c;
default:
return 0;
}
}
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