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November 27, 2010 17:08
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An easy-to-use and understand C++ library for colorspace conversions. Currently works with RGB <-> HSL/HSV. Will probably add more in the future.
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/* | |
Copyright (c) 2010, Alex Kuhl, http://www.alexkuhl.org | |
All rights reserved. | |
Redistribution and use in source and binary forms, with or without | |
modification, are permitted provided that the following conditions are | |
met: | |
* Redistributions of source code must retain the above copyright | |
notice, this list of conditions and the following disclaimer. | |
* Redistributions in binary form must reproduce the above | |
copyright notice, this list of conditions and the following | |
disclaimer in the documentation and/or other materials provided | |
with the distribution. | |
* Neither the name of the author nor the names of other | |
contributors may be used to endorse or promote products derived | |
from this software without specific prior written permission. | |
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
*/ | |
/* A small, easy-to-understand C++ library written to convert colorspaces | |
* Will convert RGB to HSV or HSL and back to RGB | |
* Note on the colors: | |
* R,G,B are ints [0,255] | |
* S,V,L are floats [0,1] | |
* H is a float [0,360) | |
* | |
* Requires the CImg library header file (testing code used version 1.3.1) | |
* http://cimg.sourceforge.net/ | |
*/ | |
#pragma once | |
#include <cmath> | |
#include <algorithm> | |
#include <vector> | |
#include <iostream> | |
#include "CImg.h" | |
using namespace std ; | |
using namespace cimg_library ; | |
void rgb_to_hsl( int r, int g, int b, float& h, float& s, float& l ) | |
{ | |
float fr = r/255.0, fg = g/255.0, fb = b/255.0 ; | |
int imax = max( max( r, g ), b ) ; | |
int imin = min( min( r, g ), b ) ; | |
float fmax = imax/255.0 ; | |
float fmin = imin/255.0 ; | |
float multiplier = ( imin == imax ) ? 0.0 : 60/( fmax - fmin ) ; | |
if( r == imax ) // red is dominant | |
{ | |
h = ( multiplier*( fg - fb ) + 360 ) ; | |
if( h >= 360 ) h -= 360 ; // take quick modulus, % doesn't work with floats | |
} | |
else if( g == imax )// green is dominant | |
h = multiplier*( fb - fr ) + 120 ; | |
else // blue is dominant | |
h = multiplier*( fr - fg ) + 240 ; | |
l = .5*( fmax + fmin ) ; | |
if( imax == imin ) | |
s = 0.0 ; | |
else if( l <= .5 ) | |
s = ( fmax - fmin )/( 2*l ) ; | |
else | |
s = ( fmax - fmin )/( 2 - 2*l ) ; | |
} | |
void hsl_to_rgb( float h, float s, float l, int& r, int& g, int& b ) | |
{ | |
float q ; | |
if( l < .5 ) | |
q = l*( 1 + s ) ; | |
else | |
q = l + s - ( l*s ) ; | |
float p = 2*l - q ; | |
h /= 360 ; | |
// t holds r, g, and b values | |
float t[ 3 ] = { h + 1/3.0, h, h - 1/3.0 } ; | |
for( int i = 0 ; i < 3 ; ++i ) | |
{ | |
if( t[ i ] < 0 ) | |
t[ i ] += 1 ; | |
else if( t[ i ] > 1 ) | |
t[ i ] -= 1 ; | |
// calculate the color | |
if( t[ i ] < 1.0/6.0 ) | |
t[ i ] = p + ( ( q - p )*6*t[ i ] ) ; | |
else if( 1.0/6.0 <= t[ i ] && t[ i ] < .5 ) | |
t[ i ] = q ; | |
else if( .5 <= t[ i ] && t[ i ] < 2.0/3.0 ) | |
t[ i ] = p + ( ( q - p )*6*( 2.0/3.0 - t[ i ] ) ) ; | |
else | |
t[ i ] = p ; | |
} | |
r = round( t[ 0 ]*255 ) ; | |
g = round( t[ 1 ]*255 ) ; | |
b = round( t[ 2 ]*255 ) ; | |
} | |
void rgb_to_hsv( int r, int g, int b, float& h, float& s, float& v ) | |
{ | |
float fr = r/255.0, fg = g/255.0, fb = b/255.0 ; | |
int imax = max( max( r, g ), b ) ; | |
int imin = min( min( r, g ), b ) ; | |
float fmax = imax/255.0 ; | |
float fmin = imin/255.0 ; | |
float multiplier = ( imin == imax ) ? 0.0 : 60/( fmax - fmin ) ; | |
if( r == imax ) // red is dominant | |
{ | |
h = ( multiplier*( fg - fb ) + 360 ) ; | |
if( h >= 360 ) h -= 360 ; // take quick modulus, % doesn't work with floats | |
} | |
else if( g == imax )// green is dominant | |
h = multiplier*( fb - fr ) + 120 ; | |
else // blue is dominant | |
h = multiplier*( fr - fg ) + 240 ; | |
if( imax == 0 ) | |
s = 0 ; | |
else | |
s = 1 - ( fmin/fmax ) ; | |
v = fmax ; | |
} | |
void hsv_to_rgb( float h, float s, float v, int& r, int& g, int& b ) | |
{ | |
h /= 60 ; | |
int hi = (int)h ; | |
float f = h - hi ; | |
// all the following *255 are to move from [0,1] to [0,255] domains | |
// because rgb are assumed [0,255] integers | |
int p = round( v*( 1 - s )*255 ) ; | |
int q = round( v*( 1 - f*s )*255 ) ; | |
int t = round( v*( 1 - ( 1 - f )*s )*255 ) ; | |
int iv = round( v*255 ) ; | |
switch( hi ) | |
{ | |
case 0: | |
r = iv ; g = t ; b = p ; | |
break ; | |
case 1: | |
r = q ; g = iv ; b = p ; | |
break ; | |
case 2: | |
r = p ; g = iv ; b = t ; | |
break ; | |
case 3: | |
r = p ; g = q ; b = iv ; | |
break ; | |
case 4: | |
r = t ; g = p ; b = iv ; | |
break ; | |
case 5: | |
r = iv ; g = p ; b = q ; | |
break ; | |
} | |
} |
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