Thumbnails

I now have code that takes the thumbnail data, converts it from YCbCr 4:2:2 to 
normal RGB, with a .ppm header, to a ppm file.

Resolution 128x96, 24bit color.

Structure is

Y1 Y2 Cr1 Cb1

Then convert Y1Cr1Cb1 to RGB, and
Y2Cr1Cr2 to RGB. (4:2:2 means every 2 Y's share the same Cr and Cb).

Basically, it can take an Exif and return a .ppm thumbnail :-)

Dennis