Add flag to Image Properties page to indicate if an image file has an embedded thumbnail.

Submitted by Jason

Assigned to Jannis Pohlmann

Link to original bug (#10333)

Description

I have a ridiculous digital picture frame that stupidly shows embedded thumbnails rather than the actual image if they exist. So I have to open each file in turn in GIMP and re-save them without thumbnails, assuming that this removes all of the thumbnails from the image file. If I could see in the file properties if the file contained an embedded thumbnail, then I could determine which files need to have the thumbnail removed rather than guess.

Apparently a JPEG can have various sources of thumbnails (from https://en.wikipedia.org/wiki/JPEG_File_Interchange_Format#Exif.2FPhotoshop_compatibility)

1. Indicated within the JFIF segment.
2. Indicated within the JFIF extension (JFXX) segment.
3. Indicated within the EXIF segment.