PHP 5.6.22 is available

Imagick::getImageHistogram

(PECL imagick 2.0.0)

Imagick::getImageHistogramGets the image histogram

Descrição

array Imagick::getImageHistogram ( void )

Returns the image histogram as an array of ImagickPixel objects.

Valor Retornado

Returns the image histogram as an array of ImagickPixel objects.

Erros

Lança ImagickException em caso de erro.

Exemplos

Exemplo #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();
    
$imagick->newImage(500500$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(200200true);
    
$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'] , $getMax0);
    
$max array_reduce($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;
}

?>

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User Contributed Notes 1 note

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4
Iddles
4 years ago
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.
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