Halide image_io JPEG saver

jpeg_io.h

#include "jo_jpeg.cpp" // http://www.jonolick.com/uploads/7/9/2/1/7921194/jo_jpeg.cpp

template<typename T>
void save_jpeg(Image<T> im, std::string filename, int quality = 90) {
    _assert(im.channels() > 0 && im.channels() < 5,
           "Can't write JPEG files that have other than 1, 2, 3, or 4 channels\n");
    
    im.copy_to_host();
    
    // convert to 8-bit and interleave
    uint8_t* buf = new uint8_t[im.width()*im.height()*im.channels()];
    int y_stride = im.width()*im.channels(),
        x_stride = im.channels();
    for (int y = 0; y < im.height(); ++y) {
        for (int x = 0; x < im.width(); ++x) {
            for (int c = 0; c < im.channels(); ++c) {
                convert(im(x, y, c), buf[y*y_stride + x*x_stride + c]);
            }
        }
    }
    
    bool success = jo_write_jpg(filename.c_str(),
                                (void*)buf,
                                im.width(),
                                im.height(),
                                im.channels(),
                                quality);

    _assert(success, "Failed to write JPEG\n");
    
    delete buf;
}