imagecolorresolve()

(PHP 4, PHP 5, PHP 7)

取得指定颜色的索引值或有可能得到的最接近的替代值

说明

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

本函数可以保证对所请求的颜色返回一个颜色索引，要么是确切值要么是所能得到最接近的替代值。

如果从文件创建了图像，只有图像中使用了的颜色会被辨析。仅出现在调色板中的颜色不会被辨析。

参见imagecolorclosest()。

Okay, so sometimes it's really IMPORTANT to get the exact color you want, only it's not *IN* the Image, and ImageColorResolve just isn't "close enough".
The following code is a disgustingly gross hack, rather slow, but it does that.
$colorcount = array();
for ($x = 0; $x < $width; $x++){
  for ($y = 0; $y < $height; $y++){
    $colorindex = imagecolorat($jpg, $x, $y);
    if (!isset($colorcount[$colorindex])){
      $colorcount[$colorindex] = 1;
    }
    else{
      $colorcount[$colorindex]++;
    }
  }
}
asort($colorcount);
reset($colorcount);
$black = imagecolorexact($jpg, 0, 0, 0);
if ($black == -1){
  $goner = key($colorcount);
  $rgb = imagecolorsforindex($jpg, $goner);
  #error_log("Need black: About to kill $goner ($rgb[red], $rgb[green], $rgb[blue]) which was only used in $colorcount[$goner] pixels", 0);
  unset($colorcount[$goner]);
  imagecolordeallocate($jpg, $goner);
  $black = imagecolorallocate($jpg, 0, 0, 0);
}
if ($black == -1){
  $black = imagecolorresolve($jpg, 0, 0, 0);
  #error_log("Damn! STILL couldn't allocate the color!", 0);
}