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Dokumen ini menggunakan Manual laman web PHP Cina Lepaskan
(PECL imagick 2.0.0)
Imagick::getImageHistogram — Gets the image histogram
Returns the image histogram as an array of ImagickPixel objects.
Returns the image histogram as an array of ImagickPixel objects.
错误时抛出 ImagickException。
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 ;
}
?>
[#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.