php中使用Imagick实现图像直方图的实现代码

<?php
$file = 'butterfly.jpg';
$size = array(
'width' => 256,
'height' => 100,
);
$image = new Imagick($file);
$histogram = array_fill_keys(range(0, 255), 0);
foreach ($image->getImageHistogram() as $pixel) {
$rgb = $pixel->getColor();
$histogram[$rgb['r']] += $pixel->getColorCount();
$histogram[$rgb['g']] += $pixel->getColorCount();
$histogram[$rgb['b']] += $pixel->getColorCount();
}
$max = max($histogram);
$threshold = ($image->getImageWidth() * $image->getImageHeight()) / 256 * 12;
if ($max > $threshold) {
$max = $threshold;
}
$image = new Imagick();
$draw = new ImagickDraw();
$image->newImage($size['width'], $size['height'], 'white');
foreach ($histogram as $x => $count) {
if ($count == 0) {
continue;
}
$draw->setStrokeColor('black');
$height = min($count, $max) / $max * $size['height'];
$draw->line($x, $size['height'], $x, $size['height'] - $height);
$image->drawImage($draw);
$draw->clear();
}
$image->setImageFormat('png');
$image->writeImage('histogram.png');
?>