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2016-01-31 00:12:03 -0600 | asked a question | What is the HOG descriptor's shape? I'm dipping my toe in pedestrian detection with OpenCV using Histogram of Oriented Gradients. I'd like to understand the descriptor better (I banged out a quick visualizer in pyplot), but I'm having trouble figuring out the output data structure. It's a very long 1D array... great for machine learning, not so easy for a human to understand. Here is my configuration, in OpenCV in Python. "img" is 64x128 and greyscale. And I get a vector of len 3780 - 7x15 blocks (not 8x16 because of the overlap), 2x2 cells per block, 9 angle bins. Is the shape (7, 15, 2, 2, 9)? Or (2, 2, 7, 15, 9)? Or (14, 30, 9)? Do the angle bins go from 0 to 180 or 180 to 0? Or is a 360 HOG? Does width come first or height? What is the OpenCV convention? |