php jepg quality 변환 http://sitehis.com/db_talk_623

http://stackoverflow.com/questions/25866819/php-image-processing-gd-jpeg-quality

exiftool로 quality 가져올 수 있음

# yum install perl-Image-ExifTool

[root@sitehis del1]# exiftool 60.jpg | grep Quality
Quality                         : 95%

$arrOutput = array();
$return_var = "";
$directOutput = exec($exiftoolCommand, $arrOutput, $return_var);

imageMagick convert command

convert original_100.jpg -quality 80 imagemagick_80.jpg

함수로 만들어본다면

$image = imagecreatefromjpeg("image.jpg"); // 파일 읽고
unlink("image.jpg"); // 해당 파일 지우고, 혹은 어디에 백업하고
imagejpeg($image,"image.jpg",50); // 50%로 저장

function compress_image($source_url, $destination_url, $quality) {
 $info = getimagesize($source_url);

 if ($info['mime'] == 'image/jpeg') $image = imagecreatefromjpeg($source_url);
 elseif ($info['mime'] == 'image/gif') $image = imagecreatefromgif($source_url);
 elseif ($info['mime'] == 'image/png') $image = imagecreatefrompng($source_url);
 
 imagejpeg($image, $destination_url, $quality); //  //save file
 return $destination_url;
}
$compressed = compress_image('source.png', 'destination.jpg', 90);

detect jpeg quality
http://stackoverflow.com/questions/17738276/detect-jpeg-image-quality

http://www.php.net/manual/en/imagick.getcompression.php

$img = new Imagick($filename);
$quality = $img->getImageCompressionQuality();

//Quality answer for your image
$quality = (101-(($width*$height)*3)/$filesize); // 직접 계산하는 법

# yum install php-pecl-imagick

$img = new Imagick($filename);

$quality = $img->getImageCompressionQuality();

<> 참고

https://cloudinary.com/blog/image_optimization_in_php