What are some cross platform and high performance image libraries for image processing (resizing and finding the color/hue histograms). No gui needed. This is for C/C++.
You might want to look at IM. It builds on several platforms, and has support for (modular) image file formats, a variety of image representations, and a wide array of transformations and operators. A GUI tool, IMLab, for demonstrating image processing operators based on the IM library is also available.