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发表于 2007-3-9 08:13:41
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显示全部楼层
下面是我收集的色彩转换方法,没有整理,需要的朋友可以参考
RGB —> HSL
var_R = ( R / 255 ) //RGB values = From 0 to 255
var_G = ( G / 255 )
var_B = ( B / 255 )
var_Min = min( var_R, var_G, var_B ) //Min. value of RGB
var_Max = max( var_R, var_G, var_B ) //Max. value of RGB
del_Max = var_Max - var_Min //Delta RGB value
L = ( var_Max + var_Min ) / 2
if ( del_Max == 0 ) //This is a gray, no chroma...
{
H = 0 //HSL results = From 0 to 1
S = 0
}
else //Chromatic data...
{
if ( L < 0.5 ) S = del_Max / ( var_Max + var_Min )
else S = del_Max / ( 2 - var_Max - var_Min )
del_R = ( ( ( var_Max - var_R ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_G = ( ( ( var_Max - var_G ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_B = ( ( ( var_Max - var_B ) / 6 ) + ( del_Max / 2 ) ) / del_Max
if ( var_R == var_Max ) H = del_B - del_G
else if ( var_G == var_Max ) H = ( 1 / 3 ) + del_R - del_B
else if ( var_B == var_Max ) H = ( 2 / 3 ) + del_G - del_R
if ( H < 0 ) ; H += 1
if ( H > 1 ) ; H -= 1
}
HSL —> RGB
if ( S == 0 ) //HSL values = From 0 to 1
{
R = L * 255 //RGB results = From 0 to 255
G = L * 255
B = L * 255
}
else
{
if ( L < 0.5 ) var_2 = L * ( 1 + S )
else var_2 = ( L + S ) - ( S * L )
var_1 = 2 * L - var_2
R = 255 * Hue_2_RGB( var_1, var_2, H + ( 1 / 3 ) )
G = 255 * Hue_2_RGB( var_1, var_2, H )
B = 255 * Hue_2_RGB( var_1, var_2, H - ( 1 / 3 ) )
}
--------------------------------------------------------------------------------
Hue_2_RGB( v1, v2, vH ) //Function Hue_2_RGB
{
if ( vH < 0 ) vH += 1
if ( vH > 1 ) vH -= 1
if ( ( 6 * vH ) < 1 ) return ( v1 + ( v2 - v1 ) * 6 * vH )
if ( ( 2 * vH ) < 1 ) return ( v2 )
if ( ( 3 * vH ) < 2 ) return ( v1 + ( v2 - v1 ) * ( ( 2 / 3 ) - vH ) * 6 )
return ( v1 )
}
RGB —> HSV
var_R = ( R / 255 ) //RGB values = From 0 to 255
var_G = ( G / 255 )
var_B = ( B / 255 )
var_Min = min( var_R, var_G, var_B ) //Min. value of RGB
var_Max = max( var_R, var_G, var_B ) //Max. value of RGB
del_Max = var_Max - var_Min //Delta RGB value
V = var_Max
if ( del_Max == 0 ) //This is a gray, no chroma...
{
H = 0 //HSV results = From 0 to 1
S = 0
}
else //Chromatic data...
{
S = del_Max / var_Max
del_R = ( ( ( var_Max - var_R ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_G = ( ( ( var_Max - var_G ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_B = ( ( ( var_Max - var_B ) / 6 ) + ( del_Max / 2 ) ) / del_Max
if ( var_R == var_Max ) H = del_B - del_G
else if ( var_G == var_Max ) H = ( 1 / 3 ) + del_R - del_B
else if ( var_B == var_Max ) H = ( 2 / 3 ) + del_G - del_R
if ( H < 0 ) ; H += 1
if ( H > 1 ) ; H -= 1
}
HSV —> RGB
if ( S == 0 ) //HSV values = From 0 to 1
{
R = V * 255 //RGB results = From 0 to 255
G = V * 255
B = V * 255
}
else
{
var_h = H * 6
var_i = int( var_h ) //Or ... var_i = floor( var_h )
var_1 = V * ( 1 - S )
var_2 = V * ( 1 - S * ( var_h - var_i ) )
var_3 = V * ( 1 - S * ( 1 - ( var_h - var_i ) ) )
if ( var_i == 0 ) { var_r = V ; var_g = var_3 ; var_b = var_1 }
else if ( var_i == 1 ) { var_r = var_2 ; var_g = V ; var_b = var_1 }
else if ( var_i == 2 ) { var_r = var_1 ; var_g = V ; var_b = var_3 }
else if ( var_i == 3 ) { var_r = var_1 ; var_g = var_2 ; var_b = V }
else if ( var_i == 4 ) { var_r = var_3 ; var_g = var_1 ; var_b = V }
else { var_r = V ; var_g = var_1 ; var_b = var_2 }
R = var_r * 255 //RGB results = From 0 to 255
G = var_g * 255
B = var_b * 255
}
}
RGB —> CMY
//RGB values = From 0 to 255
C = 1 - ( R / 255 )
M = 1 - ( G / 255 )
Y = 1 - ( B / 255 )
CMY —> RGB
R = ( 1 - C ) * 255
G = ( 1 - M ) * 255
B = ( 1 - Y ) * 255
CMY —> CMYK
var_K = 1
if ( C < var_K ) var_K = C
if ( M < var_K ) var_K = M
if ( Y < var_K ) var_K = Y
C = ( C - var_K ) / ( 1 - var_K )
M = ( M - var_K ) / ( 1 - var_K )
Y = ( Y - var_K ) / ( 1 - var_K )
K = var_K
CMYK —> CMY
C = ( C * ( 1 - K ) + K )
M = ( M * ( 1 - K ) + K )
Y = ( Y * ( 1 - K ) + K )
==========================================
RGB to HSV & HSV to RGB
// r,g,b values are from 0 to 1
// h = [0,360], s = [0,1], v = [0,1]
// if s == 0, then h = -1 (undefined)
void RGBtoHSV( float r, float g, float b, float *h, float *s, float *v )
{
float min, max, delta;
min = MIN( r, g, b );
max = MAX( r, g, b );
*v = max; // v
delta = max - min;
if( max != 0 )
*s = delta / max; // s
else {
// r = g = b = 0 // s = 0, v is undefined
*s = 0;
*h = -1;
return;
}
if( r == max )
*h = ( g - b ) / delta; // between yellow & magenta
else if( g == max )
*h = 2 + ( b - r ) / delta; // between cyan & yellow
else
*h = 4 + ( r - g ) / delta; // between magenta & cyan
*h *= 60; // degrees
if( *h < 0 )
*h += 360;
}
void HSVtoRGB( float *r, float *g, float *b, float h, float s, float v )
{
int i;
float f, p, q, t;
if( s == 0 ) {
// achromatic (grey)
*r = *g = *b = v;
return;
}
h /= 60; // sector 0 to 5
i = floor( h );
f = h - i; // factorial part of h
p = v * ( 1 - s );
q = v * ( 1 - s * f );
t = v * ( 1 - s * ( 1 - f ) );
switch( i ) {
case 0:
*r = v;
*g = t;
*b = p;
break;
case 1:
*r = q;
*g = v;
*b = p;
break;
case 2
*r = p;
*g = v;
*b = t;
break;
case 3:
*r = p;
*g = q;
*b = v;
break;
case 4:
*r = t;
*g = p;
*b = v;
break;
default: // case 5:
*r = v;
*g = p;
*b = q;
break;
}
}
=========================================
RGB to YIQ & YIQ to RGB
The YIQ system is the color primary system adopted by National Television
System Committee (NTSC) for color TV broadcasting. The YIQ color solid
is made by a linear transformation of the RGB cube. Its purpose is to
exploit certain characteristics of the human eye to maximize the utilization
of a fixed bandwidth. The human visual system is more sensitive to changes
in luminance than to changes in hue or saturation, and thus a wider bandwidth
should be dedicated to luminance than to color information. Y is similar to
perceived luminance, I and Q carry color information and some luminance
information. The Y signal usually has 4.2 MHz bandwidth in a 525 line
system. Originally, the I and Q had different bandwidths (1.5 and 0.6 MHz)
, but now they commonly have the same bandwidth of 1 MHz.
Here is the RGB -> YIQ conversion:
[ Y ] [ 0.299 0.587 0.114 ] [ R ]
[ I ] = [ 0.596 -0.275 -0.321 ] [ G ]
[ Q ] [ 0.212 -0.523 0.311 ] [ B ]
Here is the YIQ -> RGB conversion:
[ R ] [ 1 0.956 0.621 ] [ Y ]
[ G ] = [ 1 -0.272 -0.647 ] [ I ]
[ B ] [ 1 -1.105 1.702 ] [ Q ]
================================================
RGB to XYZ & XYZ to RGB
RGB values in a particular set of primaries can be transformed to and
from CIE XYZ via a 3x3 matrix transform. These transforms involve
tristimulus values, that is a set of three linear-light components that
conform to the CIE color-matching functions. CIE XYZ is a special set of
tristimulus values. In XYZ, any color is represented as a set of positive
values.
To transform from XYZ to RGB (with D65 white point), the matrix transform
used is [3]:
[ R ] [ 3.240479 -1.537150 -0.498535 ] [ X ]
[ G ] = [ -0.969256 1.875992 0.041556 ] * [ Y ]
[ B ] [ 0.055648 -0.204043 1.057311 ] [ Z ].
The range for valid R, G, B values is [0,1]. Note, this matrix has negative
coefficients. Some XYZ color may be transformed to RGB values that are
negative or greater than one. This means that not all visible colors can
be produced using the RGB system.
The inverse transformation matrix is as follows:
[ X ] [ 0.412453 0.357580 0.180423 ] [ R ] **
[ Y ] = [ 0.212671 0.715160 0.072169 ] * [ G ]
[ Z ] [ 0.019334 0.119193 0.950227 ] [ B ].
** February 20, 2000 - typo in this line of the matrix was corrected
(0.189423 to 0.180423), thanks to Michal Karczmarek, University of Toronto
================================================
http://www.cs.rit.edu/~ncs/color/t_convert.html
XYZ to CIE L*a*b* (CIELAB) & CIELAB to XYZ
CIE 1976 L*a*b* is based directly on CIE XYZ and is an attampt to linearize the perceptibility of color differences. The non-linear relations for L*, a*, and b* are intended to mimic the logarithmic response of the eye. Coloring information is referred to the color of the white point of the system, subscript n.
L* = 116 * (Y/Yn)^(1/3) - 16 for Y/Yn > 0.008856
L* = 903.3 * Y/Yn otherwise
a* = 500 * ( f(X/Xn) - f(Y/Yn) )
b* = 200 * ( f(Y/Yn) - f(Z/Zn) )
where f(t) = t^(1/3) for t > 0.008856
f(t) = 7.787 * t + 16/116 otherwise
Here Xn, Yn and Zn are the tristimulus values of the reference white.
The reverse transformation (for Y/Yn > 0.008856) is
X = Xn * ( P + a* / 500 )^3
Y = Yn * P^3
Z = Zn * ( P - b* / 200 )^3
where P = (L* + 16) / 116
================================================
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