imagecolorclosesthwb()

(PHP 4 >= 4.0.1, PHP 5, PHP 7)

取得与给定颜色最接近的色度的黑白色的索引

说明

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

取得与给定颜色最接近的色度的黑白色的索引。

参数

$image

由图象创建函数(例如imagecreatetruecolor())返回的图象资源。

$red

红色成分的值。

$green

绿色成分的值。

$blue

蓝色成分的值。

返回值

返回一个整数，是给定颜色最接近的色度的黑白色的索引。

范例

使用imagecolorclosesthwb()的例子

<?php
$im = imagecreatefromgif('php.gif');
echo 'HWB: ' . imagecolorclosesthwb($im, 116, 115, 152);
imagedestroy($im);
?>

以上例程的输出类似于：

HWB: 33

更新日志

参见

• imagecolorclosest()取得与指定的颜色最接近的颜色的索引值

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;
}
?>