Resizing images not worth it?

[galvin]

I am using Amazon's S3 service to allow users to upload images.  Since you have to pay for this service, my plan was to resize all uploaded images (maybe to a max of 200 pixels wide or something) immediately before sending them to Amazon.

 

I googled this and only thing I found said that "resizing on the fly is slow and expensive because disk space is cheaper than CPU."  Is this accurate?

 

Anyone have any thoughts on this?  I feel like I have to restrict the size of images some way because I don't wan't people uploading huge 2000x2000 images.

 

In case it matters, below is some code I have used below for resizing (albeit on my own server), so I imagine I'll use something similar for this new project which ultimately sends the image to Amazon.

 

	// This is the temporary file created by PHP 
							$uploadedfile = $_FILES['userfile']['tmp_name'];

							// Create an Image from it so we can do the resize
							$src = imagecreatefromjpeg($uploadedfile);

							// Capture the original size of the uploaded image
							list($width,$height) = getimagesize($uploadedfile);

							$newheight=70;
							$newwidth= 70;

							$tmp=imagecreatetruecolor($newwidth,$newheight);

							// this line actually does the image resizing, copying from the original
							// image into the $tmp image

							imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height); 

							// now write the resized image to disk. I have assumed that you want the
							// resized, uploaded image file to reside in the ./images subdirectory.

							$imagefolder = 'images/userimages/user' . $_SESSION['userid'] . '.jpg';
							$filename = $imagefolder;
							$_SESSION['filename'] = $filename;
							if (imagejpeg($tmp,$imagefolder,100)) {
								$imagemessage = "File is valid, and was successfully uploaded into FOLDER.\n";
								$success="yes";
								} else {
								$imagemessage = "Possible file upload attack!\n";
								$success="no";
								}
							imagedestroy($src);
							imagedestroy($tmp); // NOTE: PHP will clean up the temp file it created when the request
							// has completed.

			}

[Psycho]

If you have a need to re-size the images, then by all means re-size them. It is up to you to decide what is worth your time, effort and cost. Not some blowhard that has a blog on the internet. But, that' snot to mean you don't get the proper information before your decision and reassess your decisions thereafter.

 

Go ahead and implement a resizing script then do some tests of images with sizes you think would represent what users may upload. Is the performance acceptable? Also, be sure to try very large images - ones that you think would be much, much bigger than would be submitted. At some point the process will probably fail. You should then set a maximum size that you will accept where performance is still acceptable and the process does not fail - and reject ones that are larger.