I am working on a highly performance-critical image processing pipeline on a Jetson TX2 (with an ARM processor), which involves reading a set of images and then performing deep learning based object detection through Darknet. Darknet, written in C, has its own representation of how images are stored, which is different from how OpenCV's IplImage or a Python numpy array would store the images. Because of the requirements of my project, I am currently interfacing with this C code by first reading the images through Python (cv2.imread()) and then passing them to Darknet. But I can also call cvLoadImage() from C.
The default way OpenCV is storing the data is as one contiguous block arranged column-wise, then row-wise, then channel-wise. On the other hand, the Darknet format needs to be arranged by channel first, then by column, then by row. The following picture illustrates the difference:
This means I need to reorder the pixels from the OpenCV format to Darknet format, which is some additional overhead I would like to avoid. Is there a way to make OpenCV read the image differently, either through cv2.imread() or the IplImage format in cvLoadImage, so as to directly get the format Darknet is expecting?