This is the (possibly) final hot pixel mask that we can use to remove hot pixels from images.
It is the result of extracting the HSV-V channel from the thresholded dark frame.

Removing hot pixels needs to be the first step of any workflow, since the mask dimensions
must match those of the image being processed.

The mask is saved as a png file to avoid any jpeg artifacts that are generated
by compressing it that way. Actually, the png file is smaller than a jpeg file.

Once the mask is complete, save it and re-use it until your camera starts to develop
new hot pixels (as it gets older). I also save a second version of this mask
after rotating it to portrait mode, so that it can be applied to images captured that way.

I also save a feathered version of the mask to use when I want
a more aggressive removal of hot pixels.