Photo resize question

[floridaflatlander]

I'm saving two photos from an upload. One is a larger photo and the other is a thumb.

 

I was wondering if i used less resources to create the thumb copy of a photo from the reduced larger photo say 450*400 or create the thumb from the original that can be say 3mb and say 2500px * whatever or is it 6 one way or a half dozen another?

 

   imagecopyresampled($photo, $source, 0, 0, 0, 0, $photo_width, $photo_height, $width, $height);
//   imagecopyresampled($thumb_photo, $source, 0, 0, 0, 0, $thumb_width, $thumb_height, $width, $height); // OLD WAY
   imagecopyresampled($thumb_photo, $photo, 0, 0, 0, 0, $thumb_width, $thumb_height, $photo_width, $photo_height);

 

[requinix]

It will take much more memory to load a 2500x2500 image into memory than a 450x400. Like, >30 times more.

[floridaflatlander]

Thanks for the reply requinix, I really don't know how it works but I'm assuming that the image is already loaded to make the larger 450*400 picture so it wouldn't be loading twice(I think)

[requinix]

If you're already loading it then you can reuse it with no additional memory usage (besides what's required to make the third image).

[Barand]

There are still 30x more pixels to process. On the other hand the quality from a larger image will probably be better than from one that has already been resized. That's the trade-off

[floridaflatlander]

Thanks Barand & Requinix, this is I was looking for. I'm saving a little processing taking the thumb from the resized photo and because it's a thumb quality doesn't have to be perfect.

Thanks again