This looks great! Just a suggestion, but I think you could boost the performance of simple JPEG transformations (crop, rotate by multiples of 90 degrees, trans

This looks great! Just a suggestion, but I think you could boost the performance of simple JPEG transformations (crop, rotate by multiples of 90 degrees, transpose/transverse) by using the transformation facilities of libjpeg or libturbojpeg (which has a far nicer API). For scaling there is also epeg which works directly with the DCT coefficients. I created a Python library that uses these APIs and it beats all ImageMagick-based solutions by an order of magnitude: https://github.com/jbaiter/jpegtran-cffi https://github.com/jbaiter/jpegtran-cffi