Image Processing

Derotation

The first stage of the image processing pipeline is to align the x and y axis of the image frame with the rows and columns of the captured pattern. This requires estimation of the degree of rotation offset, then an inverse rotation transform back on the image. Derotation is done before any other steps because image rotation requires resampling and interpolation, which has the effect of blurring the image and is useful as initial noise reduction but opposes the eventual output of sharp binary segmentation. A side note is that in implementation, rescaling of the raw input image can be done in the same transform step to avoid additional interpolation overhead and degradation.

Keep in mind that rotation estimation based on aligning rows and columns can only snap to the nearest 90 degrees so absolute cardinal directions remain ambiguous and are left to be uncovered from the bit pattern itself once decoded.

Work in progress