View file File name : JpegQualityDetector.php Content :<?php namespace WebPConvert\Convert\Helpers; use ExecWithFallback\ExecWithFallback; /** * Try to detect quality of a jpeg image using various tools. * * @package WebPConvert * @author Bjørn Rosell <it@rosell.dk> * @since Class available since Release 2.0.0 */ class JpegQualityDetector { /** * Try to detect quality of jpeg using imagick extension. * * Note that the detection might fail for two different reasons: * 1) Imagick is not installed * 2) Imagick for some reason fails to detect quality for some images * * In both cases, null is returned. * * @param string $filename A complete file path to file to be examined * @return int|null Quality, or null if it was not possible to detect quality */ private static function detectQualityOfJpgUsingImagick($filename) { if (extension_loaded('imagick') && class_exists('\\Imagick')) { try { $img = new \Imagick($filename); // The required function is available as from PECL imagick v2.2.2 if (method_exists($img, 'getImageCompressionQuality')) { $quality = $img->getImageCompressionQuality(); if ($quality === 0) { // We have experienced that this Imagick method returns 0 for some images, // (even though the imagemagick binary is able to detect the quality) // ie "/test/images/quality-undetectable-with-imagick.jpg". See #208 $quality = null; } return $quality; } } catch (\Exception $e) { // Well well, it just didn't work out. // - But perhaps next method will work... } catch (\Throwable $e) { } } return null; } /** * Try to detect quality of jpeg using imagick binary. * * Note that the detection might fail for three different reasons: * 1) exec function is not available * 2) the 'identify' command is not available on the system * 3) imagemagick for some reason fails to detect quality for some images * * In the first two cases, null is returned. * In the third case, 92 is returned. This is what imagemagick returns when it cannot detect the quality. * and unfortunately we cannot distinguish between the situation where the quality is undetectable * and the situation where the quality is actually 92 (at least, I have not found a way to do so) * * @param string $filename A complete file path to file to be examined * @return int|null Quality, or null if it was not possible to detect quality */ private static function detectQualityOfJpgUsingImageMagick($filename) { if (ExecWithFallback::anyAvailable()) { // Try Imagick using exec, and routing stderr to stdout (the "2>$1" magic) try { ExecWithFallback::exec( "identify -format '%Q' " . escapeshellarg($filename) . " 2>&1", $output, $returnCode ); //echo 'out:' . print_r($output, true); if ((intval($returnCode) == 0) && (is_array($output)) && (count($output) == 1)) { return intval($output[0]); } } catch (\Exception $e) { // its ok, there are other fish in the sea } catch (\Throwable $e) { } } return null; } /** * Try to detect quality of jpeg using graphicsmagick binary. * * It seems that graphicsmagick is never able to detect the quality! - and always returns * the default quality, which is 75. * However, as this might be solved in future versions, the method might be useful one day. * But we treat "75" as a failure to detect and shall return null in that case. * * @param string $filename A complete file path to file to be examined * @return int|null Quality, or null if it was not possible to detect quality */ private static function detectQualityOfJpgUsingGraphicsMagick($filename) { if (ExecWithFallback::anyAvailable()) { // Try GraphicsMagick try { ExecWithFallback::exec( "gm identify -format '%Q' " . escapeshellarg($filename) . " 2>&1", $output, $returnCode ); if ((intval($returnCode) == 0) && (is_array($output)) && (count($output) == 1)) { $quality = intval($output[0]); // It seems that graphicsmagick is (currently) never able to detect the quality! // - and always returns 75 as a fallback // We shall therefore treat 75 as a failure to detect. (#209) if ($quality == 75) { return null; } return $quality; } } catch (\Exception $e) { } catch (\Throwable $e) { } } return null; } /** * Try to detect quality of jpeg. * * Note: This method does not throw errors, but might dispatch warnings. * You can use the WarningsIntoExceptions class if it is critical to you that nothing gets "printed" * * @param string $filename A complete file path to file to be examined * @return int|null Quality, or null if it was not possible to detect quality */ public static function detectQualityOfJpg($filename) { //trigger_error('warning test', E_USER_WARNING); // Test that file exists in order not to break things. if (!file_exists($filename)) { // One could argue that it would be better to throw an Exception...? return null; } // Try Imagick extension, if available $quality = self::detectQualityOfJpgUsingImagick($filename); if (is_null($quality)) { $quality = self::detectQualityOfJpgUsingImageMagick($filename); } if (is_null($quality)) { $quality = self::detectQualityOfJpgUsingGraphicsMagick($filename); } return $quality; } }