A couple of months ago I was working on a Trac ticket dealing with images and ran into the IMAGE_EDIT_OVERWRITE constant. I had always assumed it did as it said: when set to true and you edit an image, overwrite the original image instead of creating a new one. But a quick test revealed this was not the case. I took a quick run over to the Editing wp-config.php page on the WordPress Codex. But IMAGE_EDIT_OVERWRITE was nowhere to be found. In fact, a search of the Codex only uncovered one result: the WordPress 2.9 release notes, when the constant was first introduced. And unfortunately it said very little: Add ‘IMAGE_EDIT_OVERWRITE’ constant to control edited image save or replace, most useful for setups that have dynamic image resizing Dang. That’s not very helpful at all. So I dove head first into the rabbit hole, reviewing the code and testing behaviour in the dashboard. Default Behaviour When you edit an image, WordPress’ default behaviour (i.e. IMAGE_EDIT_OVERWRITE is false) is to create a new image and leave the original image alone. Actually it creates a new set of images as it needs to generate all the smaller size images as well. Let’s say you have the following photo… photo-1024x683.jpg
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