Image size. Pixel size of the full-resolution image referenced by catalog::Path.
If this value is provided, Image Serving uses it to avoid having to open the image to obtain the actual image size.
If catalog::Size is provided and is not the same as the actual full-resolution image size, undefined behavior may result.
Two integer numbers, each greater than 0, separated by a comma. Optional.
If the field is not present, or if the field is empty, the actual size of the image is used.