php man page for imagecolorclosestalpha

IMAGECOLORCLOSESTALPHA(3)						 1						 IMAGECOLORCLOSESTALPHA(3)

imagecolorclosestalpha - Get the index of the closest color to the specified color + alpha

SYNOPSIS
       int imagecolorclosestalpha (resource  $image, int  $red, int  $green, int  $blue, int  $alpha)

DESCRIPTION
	Returns the index of the color in the palette of the image which is "closest" to the specified RGB value and $alpha level.

PARAMETERS
	      o $
		image -An image resource, returned by one of the image creation functions, such as imagecreatetruecolor(3).

	      o $red
		-Value of red component.

	      o $green
		-Value of green component.

	      o $blue
		-Value of blue component.

	      o $alpha
		- A value between 0 and 127.  0 indicates completely opaque while 127 indicates completely transparent.

	The colors parameters are integers between 0 and 255 or hexadecimals between 0x00 and 0xFF.

RETURN VALUES
	Returns the index of the closest color in the palette.

EXAMPLES
       Example #1

	      Search for a set of colors in an image

	      <?php
	      // Start with an image and convert it to a palette-based image
	      $im = imagecreatefrompng('figures/imagecolorclosest.png');
	      imagetruecolortopalette($im, false, 255);

	      // Search colors (RGB)
	      $colors = array(
		  array(254, 145, 154, 50),
		  array(153, 145, 188, 127),
		  array(153, 90, 145, 0),
		  array(255, 137, 92, 84)
	      );

	      // Loop through each search and find the closest color in the palette.
	      // Return the search number, the search RGB and the converted RGB match
	      foreach($colors as $id => $rgb)
	      {
		  $result = imagecolorclosestalpha($im, $rgb[0], $rgb[1], $rgb[2], $rgb[3]);
		  $result = imagecolorsforindex($im, $result);
		  $result = "({$result['red']}, {$result['green']}, {$result['blue']}, {$result['alpha']})";

		  echo "#$id: Search ($rgb[0], $rgb[1], $rgb[2], $rgb[3]); Closest match: $result.
";
	      }

	      imagedestroy($im);
	      ?>

	      The above example will output something similar to:

	      #0: Search (254, 145, 154, 50); Closest match: (252, 150, 148, 0).
	      #1: Search (153, 145, 188, 127); Closest match: (148, 150, 196, 0).
	      #2: Search (153, 90, 145, 0); Closest match: (148, 90, 156, 0).
	      #3: Search (255, 137, 92, 84); Closest match: (252, 150, 92, 0).

NOTES
       Note

	      This function requires GD 2.0.1 or later (2.0.28 or later is recommended).

SEE ALSO
       imagecolorexactalpha(3), imagecolorclosest(3), imagecolorclosesthwb(3).

PHP Documentation Group 												 IMAGECOLORCLOSESTALPHA(3)