ref: 071b70df067ffa192e64511f2a88f1d4efad241b
dir: /color.c/
#include <u.h>
#include <libc.h>
#include <thread.h>
#include <draw.h>
#include <memdraw.h>
#include <geometry.h>
#include "libobj/obj.h"
#include "graphics.h"
#include "internal.h"
/*
* see also “The Importance of Being Linear”, Gritz and d'Eon, GPU Gems 3, Ch. 24, December 2007
*/
/*
* generated with:
* % seq 0 255 | awk '{$0 = $0/255; if($0 > 0.04045) $0 = (($0+0.055)/1.055)^2.4; else $0 = $0/12.92; printf("\t0x%02X,%s", int($0*255+0.5), NR%8 == 0? "\n": "")}'
*/
static uchar srgb2lineartab[] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
0x01, 0x01, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,
0x02, 0x02, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
0x04, 0x04, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05,
0x05, 0x06, 0x06, 0x06, 0x06, 0x07, 0x07, 0x07,
0x08, 0x08, 0x08, 0x08, 0x09, 0x09, 0x09, 0x0A,
0x0A, 0x0A, 0x0B, 0x0B, 0x0C, 0x0C, 0x0C, 0x0D,
0x0D, 0x0D, 0x0E, 0x0E, 0x0F, 0x0F, 0x10, 0x10,
0x11, 0x11, 0x11, 0x12, 0x12, 0x13, 0x13, 0x14,
0x14, 0x15, 0x16, 0x16, 0x17, 0x17, 0x18, 0x18,
0x19, 0x19, 0x1A, 0x1B, 0x1B, 0x1C, 0x1D, 0x1D,
0x1E, 0x1E, 0x1F, 0x20, 0x20, 0x21, 0x22, 0x23,
0x23, 0x24, 0x25, 0x25, 0x26, 0x27, 0x28, 0x29,
0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x2D, 0x2E, 0x2F,
0x30, 0x31, 0x32, 0x33, 0x33, 0x34, 0x35, 0x36,
0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E,
0x3F, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46,
0x47, 0x48, 0x49, 0x4A, 0x4C, 0x4D, 0x4E, 0x4F,
0x50, 0x51, 0x52, 0x54, 0x55, 0x56, 0x57, 0x58,
0x5A, 0x5B, 0x5C, 0x5D, 0x5F, 0x60, 0x61, 0x63,
0x64, 0x65, 0x67, 0x68, 0x69, 0x6B, 0x6C, 0x6D,
0x6F, 0x70, 0x72, 0x73, 0x74, 0x76, 0x77, 0x79,
0x7A, 0x7C, 0x7D, 0x7F, 0x80, 0x82, 0x83, 0x85,
0x86, 0x88, 0x8A, 0x8B, 0x8D, 0x8E, 0x90, 0x92,
0x93, 0x95, 0x97, 0x98, 0x9A, 0x9C, 0x9D, 0x9F,
0xA1, 0xA3, 0xA4, 0xA6, 0xA8, 0xAA, 0xAB, 0xAD,
0xAF, 0xB1, 0xB3, 0xB5, 0xB7, 0xB8, 0xBA, 0xBC,
0xBE, 0xC0, 0xC2, 0xC4, 0xC6, 0xC8, 0xCA, 0xCC,
0xCE, 0xD0, 0xD2, 0xD4, 0xD6, 0xD8, 0xDA, 0xDC,
0xDE, 0xE0, 0xE2, 0xE5, 0xE7, 0xE9, 0xEB, 0xED,
0xEF, 0xF2, 0xF4, 0xF6, 0xF8, 0xFA, 0xFD, 0xFF,
};
/*
* generated with:
* % seq 0 255 | awk '{$0 = $0/255.0; if($0 > 0.0031308) $0 = 1.055*$0^(1.0/2.4)-0.055; else $0 = $0*12.92; printf("\t0x%02X,%s", int($0*255+0.5), NR%8 == 0? "\n": "")}'
*/
static uchar linear2srgbtab[] = {
0x00, 0x0D, 0x16, 0x1C, 0x22, 0x26, 0x2A, 0x2E,
0x32, 0x35, 0x38, 0x3B, 0x3D, 0x40, 0x42, 0x45,
0x47, 0x49, 0x4B, 0x4D, 0x4F, 0x51, 0x53, 0x55,
0x56, 0x58, 0x5A, 0x5C, 0x5D, 0x5F, 0x60, 0x62,
0x63, 0x65, 0x66, 0x68, 0x69, 0x6A, 0x6C, 0x6D,
0x6E, 0x70, 0x71, 0x72, 0x73, 0x75, 0x76, 0x77,
0x78, 0x79, 0x7A, 0x7C, 0x7D, 0x7E, 0x7F, 0x80,
0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88,
0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F, 0x90,
0x91, 0x92, 0x93, 0x94, 0x94, 0x95, 0x96, 0x97,
0x98, 0x99, 0x9A, 0x9B, 0x9B, 0x9C, 0x9D, 0x9E,
0x9F, 0x9F, 0xA0, 0xA1, 0xA2, 0xA3, 0xA3, 0xA4,
0xA5, 0xA6, 0xA7, 0xA7, 0xA8, 0xA9, 0xAA, 0xAA,
0xAB, 0xAC, 0xAD, 0xAD, 0xAE, 0xAF, 0xAF, 0xB0,
0xB1, 0xB2, 0xB2, 0xB3, 0xB4, 0xB4, 0xB5, 0xB6,
0xB6, 0xB7, 0xB8, 0xB9, 0xB9, 0xBA, 0xBB, 0xBB,
0xBC, 0xBD, 0xBD, 0xBE, 0xBE, 0xBF, 0xC0, 0xC0,
0xC1, 0xC2, 0xC2, 0xC3, 0xC4, 0xC4, 0xC5, 0xC5,
0xC6, 0xC7, 0xC7, 0xC8, 0xC8, 0xC9, 0xCA, 0xCA,
0xCB, 0xCB, 0xCC, 0xCD, 0xCD, 0xCE, 0xCE, 0xCF,
0xD0, 0xD0, 0xD1, 0xD1, 0xD2, 0xD2, 0xD3, 0xD4,
0xD4, 0xD5, 0xD5, 0xD6, 0xD6, 0xD7, 0xD7, 0xD8,
0xD8, 0xD9, 0xDA, 0xDA, 0xDB, 0xDB, 0xDC, 0xDC,
0xDD, 0xDD, 0xDE, 0xDE, 0xDF, 0xDF, 0xE0, 0xE0,
0xE1, 0xE2, 0xE2, 0xE3, 0xE3, 0xE4, 0xE4, 0xE5,
0xE5, 0xE6, 0xE6, 0xE7, 0xE7, 0xE8, 0xE8, 0xE9,
0xE9, 0xEA, 0xEA, 0xEB, 0xEB, 0xEC, 0xEC, 0xED,
0xED, 0xEE, 0xEE, 0xEE, 0xEF, 0xEF, 0xF0, 0xF0,
0xF1, 0xF1, 0xF2, 0xF2, 0xF3, 0xF3, 0xF4, 0xF4,
0xF5, 0xF5, 0xF6, 0xF6, 0xF6, 0xF7, 0xF7, 0xF8,
0xF8, 0xF9, 0xF9, 0xFA, 0xFA, 0xFB, 0xFB, 0xFB,
0xFC, 0xFC, 0xFD, 0xFD, 0xFE, 0xFE, 0xFF, 0xFF,
};
/*
* Equations 5.32 and 5.30 from “Display Encoding”, Real-Time Rendering 4th ed. § 5.6
*/
//static double
//_srgb2linear(double c)
//{
// if(c > 0.04045)
// return pow((c + 0.055)/1.055, 2.4);
// return c/12.92;
//}
//
//static double
//_linear2srgb(double c)
//{
// if(c > 0.0031308)
// return 1.055*pow(c, 1.0/2.4) - 0.055;
// return 12.92*c;
//}
static double
_srgb2linear(double c)
{
c = fclamp(c, 0, 1);
return srgb2lineartab[(int)(c*255)]/255.0;
}
static double
_linear2srgb(double c)
{
c = fclamp(c, 0, 1);
return linear2srgbtab[(int)(c*255)]/255.0;
}
Color
srgb2linear(Color c)
{
c.r = _srgb2linear(c.r);
c.g = _srgb2linear(c.g);
c.b = _srgb2linear(c.b);
return c;
}
Color
linear2srgb(Color c)
{
c.r = _linear2srgb(c.r);
c.g = _linear2srgb(c.g);
c.b = _linear2srgb(c.b);
return c;
}