Question

I have a PHP script where a user can upload an image. This image is stored in the temporary directory and is returned to the user. The user can then use a javascript interface to crop the image. (x1,y2)(x2,y2) is sent to the script which is used to crop the image. It is then returned to the user for another preview and\or crop. Once the user is sufficiently satisfied he will click “save”. The temp file is copied over to the original and the temp deleted. These are not per-user images, but rather images of equipment. Any user in the organization can replace any image of equipment. This approach is good but there are a few issues:

1) Let’s say the user uploads an image for preview but then closes the browser window. I will be left with a temporary file. This can become an issue. Sure I can have a CRON clean them up but in theory I can have a ton of temporary files (this is ugly). The cron can also delete the user’s temp file during an edit.

2) To deal with number 1 I can always have a temporary file per piece of equipment, such as equip1.temp and equip1.jpg. All uploads are stored in equip1.temp, all commits are transfered to equip1.jpg. If two users are trying to upload pictures of the same piece of equipment at the same time this could mess them up (highly unlikely + not an issue, but still ugly)

3) I can always pass the image back and forth (user “uploads” image and it get’s echoed back as an <img src="base64....." />. The resulting edits + original base64 string are sent back to PHP for processing). This solution relieves the temp file issue but I noticed it takes several seconds to send high res images back and forth.

How would you deal with this situation?

Answer 1

I wouldn’t recommend #3 due to the reasons you mentioned.

I suggest you do this instead:

1. User uploads file to a random temporary name. equip1.jpg gets stored as equip1_fc8293ae82f72cf7.jpg. Be sure you script will juggle both file names around. It will allow two users to upload the same equipment, with the last one to upload being the winner, but no conflict along the way.
2. Everytime your cropper works with the temp image, you should “touch” it to update the modified time.
3. Let the user finish their edits, move the temp file in place of the final image name.
4. Have a cron, or a section of your uploader script, that deletes abandoned temp files that have a mtime older than an hour or so. You suggest this is messy, because of the potential of lots of temp files, but do you expect a lot of images to be abandoned? Garbage collection is a very standard method for this problem.