This reminds me of the time I implemented a semantic segmentation network using deconvolution and forgot to add an output layer for "this pixel is part of the b

This reminds me of the time I implemented a semantic segmentation network using deconvolution and forgot to add an output layer for "this pixel is part of the background and not part of any of the classes". Until it was fixed, background pixels got lit up in different places in output layers and drove me nuts.