epeg is a convenient, fast library that uses libjpeg to: load JPEG
images destined to be turned into thumbnails; save and retrieve
thumbnail information; and manage loading of the image, ready for
scaling, with the minimum of overhead.

epeg loads and scales large JPEG images very quickly, with a speed-up
proportional to the difference in the number of pixels in the source
image and the thumbnail. This is accomplished by decoding only the DCT
coefficients needed to reconstruct an image.  If the YUV (or GRAY8, if
the source is grayscale) format is used, then colorspace conversions
are also avoided.

WWW: http://docs.enlightenment.org/api/epeg/