Regarding the C-files: There is not much we actually can do about this, as Theano is creating these files. Maybe you can uninstall theano?
Regarding the other temporary files: In the current implementation of KNIME Image Processing, if you read or process an image, the data is duplicated for each image. The duplicated images are only written to disk in the temp folder if the used main memory exceeds a certain percentage of the heap space available to the JVM. That’s why you experience the temporary files only after a certain amount of images have been read. However, 200mb of data (even uncompressed) shouldn’t result in > 10GB of temporary data. This is something we will investigate.
Having all of that said, we’re working on a new version of KNIME Image Processing which actually doesn’t duplicate all the data all the time. Especially for very large images this is a problem which we will address. I can’t give you an estimate when it will happen, though.