Indeed there is, this answer is from this jpeg faq

Subject: 22 How can my program extract image dimensions from a JPEG file?

The header of a JPEG file consists of a series of blocks, called "markers". The image height and width are stored in a marker of type SOFn (Start Of Frame, type N). To find the SOFn you must skip over the preceding markers; you don't have to know what's in the other types of markers, just use their length words to skip over them. The minimum logic needed is perhaps a page of C code. (Some people have recommended just searching for the byte pair representing SOFn, without paying attention to the marker block structure. This is unsafe because a prior marker might contain the SOFn pattern, either by chance or because it contains a JPEG-compressed thumbnail image. If you don't follow the marker structure you will retrieve the thumbnail's size instead of the main image size.) A profusely commented example in C can be found in rdjpgcom.c in the IJG distribution (see part 2, item 15). Perl code can be found in wwwis, from http://www.tardis.ed.ac.uk/~ark/wwwis/.

That link (the tardis one) is dead, or at least it is for me but what looks like the same code is also to be found here

Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

In reply to Re: getting the dimensions of a picture (jpeg) by Random_Walk
in thread getting the dimensions of a picture (jpeg) by Anonymous Monk

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