Document dimensions of `toPixels` and `fromPixels` (#4687)
Document dimensions of `toPixels` and `fromPixels` (#4687)

DOC
I spent a long time debugging because I assumed the images were width*height (as is conventional, including in other tfjs functions). I was highly surprised to find that the shape was actually height*width!

Co-authored-by: Ping Yu <e3982a96662cc73e971d68f6aafe25f9d2e93e85@users.noreply.github.com>
tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs,tensorflow/tfjs