Imagick::getImageHistogram
(PECL imagick 2.0.0)
Imagick::getImageHistogram — Gets the image histogram
说明
Returns the image histogram as an array of ImagickPixel objects.
返回值
Returns the image histogram as an array of ImagickPixel objects.
错误／异常
错误时抛出 ImagickException。
范例
Example #1 Generates Imagick::getImageHistogram()
<?php
function getColorStatistics ( $histogramElements , $colorChannel ) {
$colorStatistics = [];
foreach ( $histogramElements as $histogramElement ) {
$color = $histogramElement -> getColorValue ( $colorChannel );
$color = intval ( $color * 255 );
$count = $histogramElement -> getColorCount ();
if ( array_key_exists ( $color , $colorStatistics )) {
$colorStatistics [ $color ] += $count ;
}
else {
$colorStatistics [ $color ] = $count ;
}
}
ksort ( $colorStatistics );
return $colorStatistics ;
}
function getImageHistogram ( $imagePath ) {
$backgroundColor = 'black' ;
$draw = new \ ImagickDraw ();
$draw -> setStrokeWidth ( 0 ); //make the lines be as thin as possible
$imagick = new \ Imagick ();
$imagick -> newImage ( 500 , 500 , $backgroundColor );
$imagick -> setImageFormat ( "png" );
$imagick -> drawImage ( $draw );
$histogramWidth = 256 ;
$histogramHeight = 100 ; // the height for each RGB segment
$imagick = new \ Imagick ( realpath ( $imagePath ));
//Resize the image to be small, otherwise PHP tends to run out of memory
//This might lead to bad results for images that are pathologically 'pixelly'
$imagick -> adaptiveResizeImage ( 200 , 200 , true );
$histogramElements = $imagick -> getImageHistogram ();
$histogram = new \ Imagick ();
$histogram -> newpseudoimage ( $histogramWidth , $histogramHeight * 3 , 'xc:black' );
$histogram -> setImageFormat ( 'png' );
$getMax = function ( $carry , $item ) {
if ( $item > $carry ) {
return $item ;
}
return $carry ;
};
$colorValues = [
'red' => getColorStatistics ( $histogramElements , \ Imagick :: COLOR_RED ),
'lime' => getColorStatistics ( $histogramElements , \ Imagick :: COLOR_GREEN ),
'blue' => getColorStatistics ( $histogramElements , \ Imagick :: COLOR_BLUE ),
];
$max = array_reduce ( $colorValues [ 'red' ] , $getMax , 0 );
$max = array_reduce ( $colorValues [ 'lime' ] , $getMax , $max );
$max = array_reduce ( $colorValues [ 'blue' ] , $getMax , $max );
$scale = $histogramHeight / $max ;
$count = 0 ;
foreach ( $colorValues as $color => $values ) {
$draw -> setstrokecolor ( $color );
$offset = ( $count + 1 ) * $histogramHeight ;
foreach ( $values as $index => $value ) {
$draw -> line ( $index , $offset , $index , $offset - ( $value * $scale ));
}
$count ++;
}
$histogram -> drawImage ( $draw );
header ( "Content-Type: image/png" );
echo $histogram ;
}
?> 用户评论:
[#1] Iddles [2011-06-20 04:02:23]
Scratched my head for a while trying to figure out why this only returned a list of coloured pixels, and seemingly no colour count. Well it turns out that for some reason, the ImagickPixel class has a "getColorCount" method, which seems a strange place for it but hey.
<?php
$image = new Imagick("thing.png");
$pixels=$image->getImageHistogram();
foreach($pixels as $p){
$colors = $p->getColor();
foreach($colors as $c){
print( "$c\t" );
}
print( "\t:\t" . $p->getColorCount() . "\n" );
}
?>
This will print out something like:
252 250 252 1 : 125
194 156 182 1 : 126
109 18 79 1 : 11440
2 117 162 1 : 12761
255 255 255 1 : 40769
...where the colums are red, green, blue, alpha, followed by the number of times that colour appears in the image.