I have a single image field, how do I set that only images of size 300x250 px can be uploaded to that field? In case any other size, the field should throw a validation error message.
There is no option/setting to limit the resolution of the uploaded images. You can limit the uploaded file size by using the setting max_file_size of the field image_upload
Hello, and how about a way to use validation callback function to do so? I did not figure out a simple way to implement any kind of validation for images (mostyl sizes of course...). Do I havee to wait the ile is loaded and use validation when the whole metabox is saved to database? Not really nice for user to wait final saving to say "hey sorry your image is not right! But I could not tell you before you saved your whole page..."
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