Fast image loading primitives

[mratsim]

On small netowrk (ResNet 18) data augmentation on CPU will be the bottleneck and the GPU will not be used fully leading to funky solutions like: https://www.sagivtech.com/2017/09/19/optimizing-pytorch-training-code/ (which uses multiprocessing to bypass Python GIL and resort to killing spawned thread)

Image loading need to be fast. Benchmarks like https://t0rakka.silvrback.com/jpeg-decoding-benchmark shows that libjpeg-turbo can be a bottleneck. See repo https://github.com/t0rakka/mango/tree/master/source/mango/jpeg and Nvidia nvJPEG https://developer.nvidia.com/nvjpeg and Nvidia DALI (Data Augmentation Library) https://github.com/NVIDIA/DALI.

Alternative libraries to look at:

• VTK: https://github.com/Kitware/VTK
• OpenCV: https://github.com/opencv/opencv
• Pillow SIMD: https://github.com/uploadcare/pillow-simd
• stb-image (Arraymancer current backend): https://github.com/nothings/stb/blob/master/stb_image.h
• Imageflow: https://github.com/imazen/imageflow
• Simd: https://github.com/ermig1979/Simd