The following information is extracted from the JPEG JFIF header. See https://www.w3.org/Graphics/JPEG/jfif3.pdf for the JFIF 1.02 specification.
Index1 Tag Name Writable Values / Notes 0 JFIFVersion no: 2 ResolutionUnit int8u: 0 = None
1 = inches
2 = cm3 XResolution int16u: 5 YResolution int16u: 7 ThumbnailWidth no 8 ThumbnailHeight no 9 ThumbnailTIFF no (raw RGB thumbnail data, extracted as a TIFF image)
Thumbnail images extracted from the JFXX segment.
Tag ID Tag Name Writable Values / Notes 0x0010 ThumbnailImage no (JPEG-format thumbnail image) 0x0011 ThumbnailTIFF no (raw palette-color thumbnail data, extracted as a TIFF image) 0x0013 ThumbnailTIFF no (raw RGB thumbnail data, extracted as a TIFF image)