Php/docs/imagick.getimagehistogram
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.
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;}?>
