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Best way to open photo image to edit in Photo Eraser for Mac® is to have it on computer’s local hard disk.
If you’d like to open photo image showed in Apple Photos organiser, please find where this image is located on computer’s hard disk, then open Photo Eraser for Mac® app press on Open, navigate to photo’s location, select it and open it. Do the necessary changes and save new image file without affecting the original. Change the name of the new file so it matches the name of the existent one and overwrite it to keep only the new edited image.