[Image-SIG] Determine byte offset of JPEG SOI marker

[Franz Buchinger]

Hi,

I want to implement some sort of "post header checksum" for JPEG
images, i.e. the checksum should only change if the actual image data
was altered, EXIF/IPTC metadata modifications should have no effect.
My plan to do this is to scan for the JPEG SOI marker, read n bytes
after this marker and calcultate an MD5/SHA checksum for this.

Can PIL tell me the byte offset of this marker?

Greetings,

Franz