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@tjlytle
Created November 17, 2009 19:19
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Class to find 'average' image color.
<?php
/**
* imageColor
*
* Shows three methods to find the 'average' image color.
*
* Each function expects a gd image object.
*
* imageColor::averageResize($image) resizing to 1px, and checking the color.
* imageColor::averageBorder($image) find the average color of all border pixels.
* imageColor::averageImage($image) find the average color of all pixels.
*
*/
class imageColor
{
function scanLine($image, $height, $width, $axis, $line)
{
$i = 0;
if("x" == $axis){
$limit = $width;
$y = $line;
$x =& $i;
if(-1 == $line){
$y = 0;
$y2 = $width -1;
$x2 =& $i;
}
} else {
$limit = $height;
$x = $line;
$y =& $i;
if(-1 == $line){
$x = 0;
$x2 = $width -1;
$y2 =& $i;
}
}
$colors = array();
if(-1 == $line){
for($i = 0; $i < $limit; $i++){
self::addPixel($colors, $image, $x, $y);
self::addPixel($colors, $image, $x2, $y2);
}
} else {
for($i = 0; $i < $limit; $i++){
self::addPixel($colors, $image, $x, $y);
}
}
return $colors;
}
function addPixel(&$colors, $image, $x, $y)
{
$rgb = imagecolorat($image, $x, $y);
$color = imagecolorsforindex($image, $rgb);
$colors['red'][] = $color['red'];
$colors['green'][] = $color['green'];
$colors['blue'][] = $color['blue'];
}
function totalColors($color, $colors)
{
$color['red'] += array_sum($colors['red']);
$color['green'] += array_sum($colors['green']);
$color['blue'] += array_sum($colors['blue']);
return $colors;
}
function averageTotal($color, $count)
{
$color['red'] = intval($color['red']/$count);
$color['green'] = intval($color['green']/$count);
$color['blue'] = intval($color['blue']/$count);
return $color;
}
function averageResize($image)
{
$width = imagesx($image);
$height = imagesy($image);
$pixel = imagecreatetruecolor(1, 1);
imagecopyresampled($pixel, $image, 0, 0, 0, 0, 1, 1, $width, $height);
$rgb = imagecolorat($pixel, 0, 0);
$color = imagecolorsforindex($pixel, $rgb);
return $color;
}
function averageBorder($image)
{
$width = imagesx($image);
$height = imagesy($image);
$colors = self::scanLine($image, $height, $width, 'x', -1);
self::totalColors(&$color, $colors);
$colors = self::scanLine($image, $height, $width, 'y', -1);
self::totalColors(&$color, $colors);
$borderSize = ($height=$width)*2;
self::averageTotal(&$color, $borderSize);
return $color;
}
function averageImage($image)
{
$width = imagesx($image);
$height = imagesy($image);
$colors = array();
for($line = 0; $line < $height; $line++){
$colors = self::scanLine($image, $height, $width, 'x', $line);
self::totalColors(&$color, $colors);
}
$count = $width*$height;
self::averageTotal(&$color, $count);
return $color;
}
}
?>
@tjlytle
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Author

tjlytle commented Aug 29, 2010

The result of the lengthy StackOverflow answer.

@jorgebraz
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Thank you for the nice work, it has been very helpful.
I think you have a little mistake in line 109 "$borderSize = ($height=$width)_2;" should be "$borderSize = ($height+$width)_2;"

;)

@ve3
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ve3 commented Sep 21, 2022

Updated for work with PHP 8.1

<?php
/**
 * imageColor 
 * 
 * @link https://gist.github.com/tjlytle/237185 Original source code.
 * 
 * Shows three methods to find the 'average' image color.
 * 
 * Each function expects a gd image object.
 * 
 * imageColor::averageResize($image) resizing to 1px, and checking the color.
 * imageColor::averageBorder($image) find the average color of all border pixels.
 * imageColor::averageImage($image)  find the average color of all pixels.
 * 
 */
class ImageColor
{
	protected static function scanLine($image, $height, $width, $axis, $line)
	{
		$i = 0;
		
		if("x" == $axis){
			$limit = $width;
			$y = $line;
			$x =& $i;
			
			if(-1 == $line){
				$y = 0;
				$y2 = $width -1;
				$x2 =& $i;	
			}
		} else {
			$limit = $height;
			$x = $line;
			$y =& $i;
			
			if(-1 == $line){
				$x = 0;
				$x2 = $width -1;
				$y2 =& $i;	
			}
		}
		
		$colors = array();
		
		if(-1 == $line){
			for($i = 0; $i < $limit; $i++){
				static::addPixel($colors, $image, $x, $y);
				static::addPixel($colors, $image, $x2, $y2);
			}
		} else {
			for($i = 0; $i < $limit; $i++){
				static::addPixel($colors, $image, $x, $y);
			}
		}
		
		return $colors;
	}
	
	protected static function addPixel(&$colors, $image, $x, $y)
	{
		$rgb = imagecolorat($image, $x, $y);
		$color = imagecolorsforindex($image, $rgb);
		$colors['red'][] = $color['red'];
		$colors['green'][] = $color['green'];
		$colors['blue'][] = $color['blue'];
	}
	
	protected static function totalColors(&$color, $colors)
	{
		$color['red'] += array_sum($colors['red']);
		$color['green'] += array_sum($colors['green']);
		$color['blue'] += array_sum($colors['blue']);

		return $colors;
	}
	
	protected static function averageTotal(&$color, $count)
	{
		$color['red'] = intval($color['red']/$count);
		$color['green'] = intval($color['green']/$count);
		$color['blue'] = intval($color['blue']/$count);
		
		return $color;
	}
	
	public static function averageResize($image)
	{
		$width = imagesx($image);
		$height = imagesy($image);
		
		$pixel = imagecreatetruecolor(1, 1);
		imagecopyresampled($pixel, $image, 0, 0, 0, 0, 1, 1, $width, $height);
		$rgb = imagecolorat($pixel, 0, 0);
		$color = imagecolorsforindex($pixel, $rgb);
		
		return $color;
	}
	
	public static function averageBorder($image)
	{
		$width = imagesx($image);
		$height = imagesy($image);

		$pixel = imagecreatetruecolor(1, 1);
		$rgb = imagecolorat($pixel, 0, 0);
		$color = imagecolorsforindex($pixel, $rgb);
		
		$colors = static::scanLine($image, $height, $width, 'x', 0);
		static::totalColors($color, $colors);
		
		$colors = static::scanLine($image, $height, $width, 'y', -1);
		static::totalColors($color, $colors);

		$borderSize = ($height+$width)*2;
		static::averageTotal($color, $borderSize);
		
		return $color;
	}
	
	public static function averageImage($image)
	{
		$width = imagesx($image);
		$height = imagesy($image);
		
		$colors = [];

		$pixel = imagecreatetruecolor(1, 1);
		$rgb = imagecolorat($pixel, 0, 0);
		$color = imagecolorsforindex($pixel, $rgb);
		
		for($line = 0; $line < $height; $line++){
			$colors = static::scanLine($image, $height, $width, 'x', $line);
			static::totalColors($color, $colors);
		}
		
		$count = $width*$height;
		static::averageTotal($color, $count);
		
		return $color;
	}
}

Fixed a lot of errors. I'm not sure is it work correctly compared to original code.

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