So with a little hand waving to center the letter and assuming an image of the letter with 1 bit per pixel. Simply moving down the image center vertically, counting the number of white to black and black to white transitions and the row of the lowest black to white transition is easier and more reliable.

But for fans of symmetry read on. H is symmetric (flip 180 degrees) in the x and y axes, U is symmetric in the y axis but not x axis, and S is not symmetric in x and y axes.

For x sym test, XOR the top half of the image with the bottom half. Think of this as folding the image in half along the x axis. XOR the pixels that overlay each other. If the result has mostly zeroes, the image is sym about the x axis. Repeat for y sym test but XOR left and right halves. Based on the x sym and y sym tests, guess the letter.

This might fail because of noisy images, poor lighting, choosing fonts where the letters are not symmetric about x and y axes, etc.