I have several hundreds of category Images containing a .png extension. But I want to convert that images to .jpg (outside of Magento and not part of that question) and then reupload them to media/catalog/category and tell Magento to use the new .jpg extension for all .png Category Images. Including Thumbnail Image and Image field.
I found the quite similar Question Migrating All Product Images in Magento from PNGs to JPEGs but the difference is that I want to change Category Images and not Product Images.
Can someone tell me how to change that script or a different approach, please? Updating all Categories in the backend manually would take to much time.