Working with Floating Point images in OpenCV can be tricky, especially if you've so far only worked with 8-bit (uchar) images. In this tutorial, I'll describe how to create a floating point image, how to access and modify it, and how to save it to or load it from disk.
There are many scenarios where we might wish to work with floating point pixel values. In my case, I'm working on High Dynamic Range Imaging which inherently deals with floats rather than integer values. A more common scenario is that you want to apply a series of operations to an image in a processing pipeline, and you'd like to maintain high precision throughout, then clamp the values at the end and round to integers. In that case you could take an 8-bit image at the beginning, convert it to 32-bit floats, perform all your operations on it, then convert back to 8-bit at the end so you only have one instance of integer rounding error.