Question

What’s the most efficient way to resize large images in PHP?

I’m currently using the GD function imagecopyresampled to take high resolution images, and cleanly resize them down to a size for web viewing (roughly 700 pixels wide by 700 pixels tall).

This works great on small (under 2 MB) photos and the entire resize operation takes less than a second on the server. However, the site will eventually service photographers who may be uploading images up to 10 MB in size (or images up to 5000×4000 pixels in size).

Doing this kind of resize operation with large images tends to increase the memory usage by a very large margin (larger images can spike the memory usage for the script past 80 MB). Is there any way to make this resize operation more efficient? Should I be using an alternate image library such as ImageMagick?

Right now, the resize code looks something like this

function makeThumbnail($sourcefile, $endfile, $thumbwidth, $thumbheight, $quality) {     // Takes the sourcefile (path/to/image.jpg) and makes a thumbnail from it     // and places it at endfile (path/to/thumb.jpg).      // Load image and get image size.     $img = imagecreatefromjpeg($sourcefile);     $width = imagesx( $img );     $height = imagesy( $img );      if ($width > $height) {         $newwidth = $thumbwidth;         $divisor = $width / $thumbwidth;         $newheight = floor( $height / $divisor);     } else {         $newheight = $thumbheight;         $divisor = $height / $thumbheight;         $newwidth = floor( $width / $divisor );     }      // Create a new temporary image.     $tmpimg = imagecreatetruecolor( $newwidth, $newheight );      // Copy and resize old image into new image.     imagecopyresampled( $tmpimg, $img, 0, 0, 0, 0, $newwidth, $newheight, $width, $height );      // Save thumbnail into a file.     imagejpeg( $tmpimg, $endfile, $quality);      // release the memory     imagedestroy($tmpimg);     imagedestroy($img); 

Answer 1

People say that ImageMagick is much faster. At best just compare both libraries and measure that.

1. Prepare 1000 typical images.
2. Write two scripts — one for GD, one for ImageMagick.
3. Run both of them a few times.
4. Compare results (total execution time, CPU and I/O usage, result image quality).

Something which the best everyone else, could not be the best for you.

Also, in my opinion, ImageMagick has much better API interface.