Imagick::getImageHistogram

(PECL imagick 2, PECL imagick 3)

Imagick::getImageHistogram — Gets the image histogram

说明

public Imagick::getImageHistogram(): array

Returns the image histogram as an array of ImagickPixel objects.

参数

此函数没有参数。

返回值

Returns the image histogram as an array of ImagickPixel objects.

错误／异常

错误时抛出 ImagickException。

示例

示例 #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;
}

?>

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Iddles
13 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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备份地址：http://www.lvesu.com/blog/php/imagick.getimagehistogram.php