Issue Converting JPG to PNG and Compressing | PHP - php

Question

Essentially I would like to upload an image to a web server and also convert it from JPG to PNG with as much compression as possible.
The following is what I currently have to upload a JPG image from a mobile device:
<?PHP
if(!empty($_FILES['uploaded_file']))
{
$path = "uploads/";
$path = $path . basename( $_FILES['uploaded_file']['name']);
if(move_uploaded_file($_FILES['uploaded_file']['tmp_name'], $path)) {
echo "The file ". basename( $_FILES['uploaded_file']['name']).
" has been uploaded";
} else{
echo "There was an error uploading the file, please try again!";
}
}
?>
This works well but I must now convert the file to a PNG and compress - for this I have tried working with code like this, but I do not understand how to implement it and also add compression.
$image = imagecreatefromjpeg( "image.jpg" );
imagealphablending($image, true);
imagepng($image, "image.png");
Is something converting and compressing possible?

Answer 1

In official php documentation: https://www.php.net/imagepng
It is stated that the function signature for imagepng is:
imagepng ( resource $image , mixed $to = null , int $quality = -1 , int $filters = -1 ) : bool
Parameter quality:
- quality
Compression level: from 0 (no compression) to 9.
The default (-1) uses the zlib compression default.
For more information see the » zlib manual.
Therefore when you save the image as PNG in below code, it's already compressed:
$image = imagecreatefromjpeg( "image.jpg" );
imagealphablending($image, true);
imagepng($image, "image.png");
If you want higher compression (i.e.: smaller size, worse image quality), then you just need to put higher number in quality parameter (closer to 9 = heavier compression)
$image = imagecreatefromjpeg( "image.jpg" );
imagealphablending($image, true);
imagepng($image, "image.png", 9); // heavily compressed
You need to be careful though that imagejpeg https://www.php.net/imagejpeg also have quality parameter, but that one ranges from 0 (worst quality, smaller file) to 100 (best quality, biggest file).