GD and Image 函数
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imagecolorclosesthwb

(PHP 4 >= 4.0.1, PHP 5)

imagecolorclosesthwb 取得与给定颜色最接近的色度的黑白色的索引

说明

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

GD and Image 函数
在线手册:中文 英文
PHP手册
PHP手册 - N: 取得与给定颜色最接近的色度的黑白色的索引

用户评论:

Xong (22-Jun-2009 11:56)

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;
}
?>