Gets the image histogram

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- PHP Manual
- Imagick
- Gets the image histogram

# Imagick::getImageHistogram

(PECL imagick 2, PECL imagick 3)

Imagick::getImageHistogram — Gets the image histogram

### Description

public Imagick::getImageHistogram(): array

Returns the image histogram as an array of ImagickPixel objects.

### Parameters

This function has no parameters.

### Return Values

Returns the image histogram as an array of ImagickPixel objects.

### Errors/Exceptions

Throws ImagickException on error.

### Examples

Example #1 Generates Imagick::getImageHistogram()

    <?phpfunction 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;}?>