peach
November 30, 2008, 1:45pm
1
I’ve been searching the net for many hours, finding functions that convert from one color space to the other but I have not yet found a set op functions that can help me convert, and convert back again.
about color spaces:
The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additive primary colors, red, green, and blue.
The main purpose of the RGB color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. B...
HSL (for hue, saturation, lightness) and HSV (for hue, saturation, value; also known as HSB, for hue, saturation, brightness) are alternative representations of the RGB color model, designed in the 1970s by computer graphics researchers. In these models, colors of each hue are arranged in a radial slice, around a central axis of neutral colors which ranges from black at the bottom to white at the top.
The HSL representation models the way different paints mix together to create color in the real...
I believe this is an accurate function that does RGB->HSL but it’s way above my level of programming, I haven’t been able to figure out how to revert it:
function rgb2hsl($rgb){
$clrR = ($rgb[0]);
$clrG = ($rgb[1]);
$clrB = ($rgb[2]);
$clrMin = min($clrR, $clrG, $clrB);
$clrMax = max($clrR, $clrG, $clrB);
$deltaMax = $clrMax - $clrMin;
$L = ($clrMax + $clrMin) / 510;
if (0 == $deltaMax){
$H = 0;
$S = 0;
}
else{
if (0.5 > $L){
$S = $deltaMax / ($clrMax + $clrMin);
}
else{
$S = $deltaMax / (510 - $clrMax - $clrMin);
}
if ($clrMax == $clrR) {
$H = ($clrG - $clrB) / (6.0 * $deltaMax);
}
else if ($clrMax == $clrG) {
$H = 1/3 + ($clrB - $clrR) / (6.0 * $deltaMax);
}
else {
$H = 2 / 3 + ($clrR - $clrG) / (6.0 * $deltaMax);
}
if (0 > $H) $H += 1;
if (1 < $H) $H -= 1;
}
return array($H, $S,$L);
}
If anyone knows of a set of PHP HSL/RGB color space conversion functions, plz link me up! Or if anyone wants to have a go at reversing this rgb2hsl function, good luck!
peach
November 30, 2008, 1:59pm
2
Here are the color conversion functions from color module in Drupal CMS, but I keep getting greys when I try to do RGB->HSL, it seems to never give me a non-zero saturation level:
/**
* Convert a HSL triplet into RGB
*/
function _color_hsl2rgb($hsl) {
$h = $hsl[0];
$s = $hsl[1];
$l = $hsl[2];
$m2 = ($l <= 0.5) ? $l * ($s + 1) : $l + $s - $l*$s;
$m1 = $l * 2 - $m2;
return array(_color_hue2rgb($m1, $m2, $h + 0.33333),
_color_hue2rgb($m1, $m2, $h),
_color_hue2rgb($m1, $m2, $h - 0.33333));
}
/**
* Helper function for _color_hsl2rgb().
*/
function _color_hue2rgb($m1, $m2, $h) {
$h = ($h < 0) ? $h + 1 : (($h > 1) ? $h - 1 : $h);
if ($h * 6 < 1) return $m1 + ($m2 - $m1) * $h * 6;
if ($h * 2 < 1) return $m2;
if ($h * 3 < 2) return $m1 + ($m2 - $m1) * (0.66666 - $h) * 6;
return $m1;
}
/**
* Convert an RGB triplet to HSL.
*/
function _color_rgb2hsl($rgb) {
$r = $rgb[0];
$g = $rgb[1];
$b = $rgb[2];
$min = min($r, min($g, $b));
$max = max($r, max($g, $b));
$delta = $max - $min;
$l = ($min + $max) / 2;
$s = 0;
if ($l > 0 && $l < 1) {
$s = $delta / ($l < 0.5 ? (2 * $l) : (2 - 2 * $l));
}
$h = 0;
if ($delta > 0) {
if ($max == $r && $max != $g) $h += ($g - $b) / $delta;
if ($max == $g && $max != $b) $h += (2 + ($b - $r) / $delta);
if ($max == $b && $max != $r) $h += (4 + ($r - $g) / $delta);
$h /= 6;
}
return array($h, $s, $l);
}
Is this any good?
<?php
function RGB_TO_HSV ($R, $G, $B) // RGB Values:Number 0-255
{ // HSV Results:Number 0-1
$HSL = array();
$var_R = ($R / 255);
$var_G = ($G / 255);
$var_B = ($B / 255);
$var_Min = min($var_R, $var_G, $var_B);
$var_Max = max($var_R, $var_G, $var_B);
$del_Max = $var_Max - $var_Min;
$V = $var_Max;
if ($del_Max == 0)
{
$H = 0;
$S = 0;
}
else
{
$S = $del_Max / $var_Max;
$del_R = ( ( ( $max - $var_R ) / 6 ) + ( $del_Max / 2 ) ) / $del_Max;
$del_G = ( ( ( $max - $var_G ) / 6 ) + ( $del_Max / 2 ) ) / $del_Max;
$del_B = ( ( ( $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++;
if (H>1) $H--;
}
$HSL['H'] = $H;
$HSL['S'] = $S;
$HSL['V'] = $V;
return $HSL;
}
function HSV_TO_RGB ($H, $S, $V) // HSV Values:Number 0-1
{ // RGB Results:Number 0-255
$RGB = array();
if($S == 0)
{
$R = $G = $B = $V * 255;
}
else
{
$var_H = $H * 6;
$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;
$G = $var_G * 255;
$B = $var_B * 255;
}
$RGB['R'] = $R;
$RGB['G'] = $G;
$RGB['B'] = $B;
return $RGB;
}
?>
Source
peach
November 30, 2008, 3:07pm
4
dont think so, it does HSV conversion, HSV is a different color space like Hue/Saturation/Brightness, in which both saturation and brightness are very different values.
I need HSL because 100% lightness has to be white and 0% Lightness has to be black, with HSV 100% of value V can be a bright orange
depiction of the difference:
Ah, I see.
Sorry, I misread your post, far to many acronyms and not enough coffee!
Good luck
peach
December 4, 2008, 4:17pm
6
in case anyone is interested, I did manage to make it work using just the functions in Drupal. Those functions are open source so you may use them, if you comply to the GNU license.
the important thing I forgot that in 2 of the functions you have to supply a second argument that enable normalization of color values from 0-255 to fractions.
<?php
function _color_rgb2hsl($rgb) {
$r = $rgb[0];
$g = $rgb[1];
$b = $rgb[2];
$min = min($r, min($g, $b));
$max = max($r, max($g, $b));
$delta = $max - $min;
$l = ($min + $max) / 2;
$s = 0;
if ($l > 0 && $l < 1) {
$s = $delta / ($l < 0.5 ? (2 * $l) : (2 - 2 * $l));
}
$h = 0;
if ($delta > 0) {
if ($max == $r && $max != $g) $h += ($g - $b) / $delta;
if ($max == $g && $max != $b) $h += (2 + ($b - $r) / $delta);
if ($max == $b && $max != $r) $h += (4 + ($r - $g) / $delta);
$h /= 6;
}
return array($h, $s, $l);
}
function _color_hsl2rgb($hsl) {
$h = $hsl[0];
$s = $hsl[1];
$l = $hsl[2];
$m2 = ($l <= 0.5) ? $l * ($s + 1) : $l + $s - $l*$s;
$m1 = $l * 2 - $m2;
return array(_color_hue2rgb($m1, $m2, $h + 0.33333),
_color_hue2rgb($m1, $m2, $h),
_color_hue2rgb($m1, $m2, $h - 0.33333));
}
/**
* Helper function for _color_hsl2rgb().
*/
function _color_hue2rgb($m1, $m2, $h) {
$h = ($h < 0) ? $h + 1 : (($h > 1) ? $h - 1 : $h);
if ($h * 6 < 1) return $m1 + ($m2 - $m1) * $h * 6;
if ($h * 2 < 1) return $m2;
if ($h * 3 < 2) return $m1 + ($m2 - $m1) * (0.66666 - $h) * 6;
return $m1;
}
/**
* Convert a hex color into an RGB triplet.
*/
function _color_unpack($hex, $normalize = false) {
if (strlen($hex) == 4) {
$hex = $hex[1] . $hex[1] . $hex[2] . $hex[2] . $hex[3] . $hex[3];
}
$c = hexdec($hex);
for ($i = 16; $i >= 0; $i -= 8) {
$out[] = (($c >> $i) & 0xFF) / ($normalize ? 255 : 1);
}
return $out;
}
/**
* Convert an RGB triplet to a hex color.
*/
function _color_pack($rgb, $normalize = false) {
foreach ($rgb as $k => $v) {
$out |= (($v * ($normalize ? 255 : 1)) << (16 - $k * 8));
}
return '#'. str_pad(dechex($out), 6, 0, STR_PAD_LEFT);
}
/* $testrgb = array(0.2,0.75,0.4); //RGB to start with
print_r($testrgb); */
print "Hex: ";
$testhex = "#C5003E";
print $testhex;
$testhex2rgb = _color_unpack($testhex,true);
print "<br />RGB: ";
var_dump($testhex2rgb);
print "<br />HSL color module: ";
$testrgb2hsl = _color_rgb2hsl($testhex2rgb); //Converteren naar HSL
var_dump($testrgb2hsl);
print "<br />RGB: ";
$testhsl2rgb = _color_hsl2rgb($testrgb2hsl); // En weer terug naar RGB
var_dump($testhsl2rgb);
print "<br />Hex: ";
$testrgb2hex = _color_pack($testhsl2rgb,true);
var_dump($testrgb2hex);
?>
There seems to be an error, input hex is #C5003 E output hex is #C5003 D might have to do with float rounding errors.
BTW with some PHP 5.3 and closure love…
function _color_hsl2rgb ( $hsl )
{
$h = $hsl[0]; $s = $hsl[1]; $l = $hsl[2];
$m2 = ( $l <= 0.5 ) ? $l * ( $s + 1 ) : $l + $s - $l * $s;
$m1 = $l * 2 - $m2;
$hue = function ( $base ) use ( $m1, $m2 ) {
$base = ( $base < 0 ) ? $base + 1 : ( ( $base > 1 ) ? $base - 1 : $base );
if ( $base * 6 < 1 ) return $m1 + ( $m2 - $m1 ) * $base * 6;
if ( $base * 2 < 1 ) return $m2;
if ( $base * 3 < 2 ) return $m1 + ( $m2 - $m1 ) * ( 0.66666 - $base ) * 6;
return $m1;
}
return array( $hue( $h + 0.33333 ), $hue( $h ), $hue( $h - 0.33333 ) );
}
