[edit] Last updated: Fri, 28 Jun 2013

imagecolorclosesthwb

(PHP 4 >= 4.0.1, PHP 5)

imagecolorclosesthwb — Get the index of the color which has the hue, white and blackness

Description

int imagecolorclosesthwb ( resource $image , int $red , int $green , int $blue )

Get the index of the color which has the hue, white and blackness nearest the given color.

Parameters

image: An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
red: Value of red component.
green: Value of green component.
blue: Value of blue component.

Return Values

Returns an integer with the index of the color which has the hue, white and blackness nearest the given color.

Examples

Example #1 Example of using imagecolorclosesthwb()


<?php
$im = imagecreatefromgif('php.gif');

echo 'HWB: ' . imagecolorclosesthwb($im, 116, 115, 152);

imagedestroy($im);
?>

The above example will output something similar to:

HWB: 33

Changelog

Version	Description
5.3.0	This function is now available on Windows


I have written a function which uses the deltaE-function of the CMC.


It returns much better results than imagecolorclosestHWB() or imageColorClosest().





A test-script is online on http://www.fuhrpark-software.de/spielwiese/color.php?color=ffff00





<?php


/*


 * Returns the index of the palette-color which is most similar


 * to $givenColor.


 * 


 * $givenColor and the colors in $palette should be either


 * formatted as (#)rrggbb


 * (e. g. "ff0000", "4da4f3" or "#b5d7f3")


 * or arrays with values for red, green and blue


 * (e. g. $givenColor = array( 0xff, 0x00, 0x00 ) )


 *


 * References:


 * function rgb2lab


 *   - http://www.f4.fhtw-berlin.de/~barthel/ImageJ/ImageJ.htm


 * 


 * function rgb2lab & function deltaE


 *   - http://www.brucelindbloom.com


 */


function getNearestColor(


  $givenColor,


  $palette = array( 'blue' => '43aafd','red' => 'fe6256','green' => '64b949','yellow' => 'fcf357',


    'black' => '656565','white' => 'fdfdfd','orange' => 'fea800','purple' => '9773fe')


) {


  if(!function_exists('rgb2lab')) {


    function rgb2lab($rgb) {


      $eps = 216/24389; $k = 24389/27;


      // reference white D50


      $xr = 0.964221; $yr = 1.0; $zr = 0.825211;





      $rgb[0] = $rgb[0]/255; //R 0..1


      $rgb[1] = $rgb[1]/255; //G 0..1


      $rgb[2] = $rgb[2]/255; //B 0..1





      // assuming sRGB (D65)


      $rgb[0] = ($rgb[0] <= 0.04045)?($rgb[0]/12.92):pow(($rgb[0]+0.055)/1.055,2.4);


      $rgb[1] = ($rgb[1] <= 0.04045)?($rgb[1]/12.92):pow(($rgb[1]+0.055)/1.055,2.4);


      $rgb[2] = ($rgb[2] <= 0.04045)?($rgb[2]/12.92):pow(($rgb[2]+0.055)/1.055,2.4);





      // sRGB D50


      $x =  0.4360747*$rgb[0] + 0.3850649*$rgb[1] + 0.1430804 *$rgb[2];


      $y =  0.2225045*$rgb[0] + 0.7168786*$rgb[1] + 0.0606169 *$rgb[2];


      $z =  0.0139322*$rgb[0] + 0.0971045*$rgb[1] + 0.7141733 *$rgb[2];





      $xr = $x/$xr; $yr = $y/$yr; $zr = $z/$zr;





      $fx = ($xr > $eps)?pow($xr, 1/3):($fx = ($k * $xr + 16) / 116);


      $fy = ($yr > $eps)?pow($yr, 1/3):($fy = ($k * $yr + 16) / 116);


      $fz = ($zr > $eps)?pow($zr, 1/3):($fz = ($k * $zr + 16) / 116);





      $lab = array();


      $lab[] = round(( 116 * $fy ) - 16);


      $lab[] = round(500*($fx-$fy));


      $lab[] = round(200*($fy-$fz));      


      return $lab;


    }


  }


  


  if(!function_exists('deltaE')) {


    function deltaE($lab1, $lab2) {


      // CMC 1:1


      $l = 1; $c = 1;


      


      $c1 = sqrt($lab1[1]*$lab1[1]+$lab1[2]*$lab1[2]);


      $c2 = sqrt($lab2[1]*$lab2[1]+$lab2[2]*$lab2[2]);


      


      $h1 = (((180000000/M_PI) * atan2($lab1[1],$lab1[2]) + 360000000) % 360000000)/1000000;





      $t = (164 <= $h1 AND $h1 <= 345)?(0.56 + abs(0.2 * cos($h1+168))):(0.36 + abs(0.4 * cos($h1+35)));


      $f = sqrt(pow($c1,4)/(pow($c1,4) + 1900));


      


      $sl = ($lab1[0] < 16)?(0.511):((0.040975*$lab1[0])/(1 + 0.01765*$lab1[0]));


      $sc = (0.0638 * $c1)/(1 + 0.0131 * $c1) + 0.638;


      $sh = $sc * ($f * $t + 1 -$f);


      


      return sqrt(


        pow(($lab1[0]-$lab2[0])/($l * $sl),2) + 


        pow(($c1-$c2)/($c * $sc),2) + 


        pow(sqrt(


              ($lab1[1]-$lab2[1])*($lab1[1]-$lab2[1]) + 


              ($lab1[2]-$lab2[2])*($lab1[2]-$lab2[2]) + 


              ($c1-$c2)*($c1-$c2)


            )/$sh,2)


      );


    }


  }


  


  if(!function_exists('str2rgb')) {


    function str2rgb($str)


    {


      $str = preg_replace('~[^0-9a-f]~','',$str);


      $rgb = str_split($str,2);


      for($i=0;$i<3;$i++)


        $rgb[$i] = intval($rgb[$i],16);





      return $rgb;


    }


  }


  


  $givenColorRGB = is_array($givenColor?$givenColor:str2rgb($givenColor);





  $min = 0xffff;


  $return = NULL;


  


  foreach($palette as $key => $color) {


    $color = is_array($color)?$color:str2rgb($color);


    if($min >= ($deltaE = deltaE(rgb2lab($color),rgb2lab($givenColorRGB))))


    {


      $min = $deltaE;


      $return = $key;


    }


  }


  


  return $return;


}


?>

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