Hi snibgo,
you have been very helpful in this topic and i appreciate you very much. I see what you mean and so xdensity / ydensity is the answer. I just have to add the code and i am finished with app0. I am kind of working backward with parsing as i have tackled more complex segments such as exif and icc profile headers. I have allready extracted frame headers and added 100% validation. I figure it is time to deal with app0 and also to validate da headers against the frame header. I did not expect a value of 100 (0x64) so i thought that it will be better if i ask some jpeg professionals. I appreciate all of the help. 