Finally finished an algo to check an image for grouping of pixels that will form a rectangular area. I got the grouping to work on one image, but found it was utterly failing on another. I went through every step of the algo and still could not find the solution. The 128x128 image was working, but the 128x16 image was not. I knew it had something to do with the dimensions. Started thinking it was overflowing a buffer somewhere. So I started putting asserts in the functions that abstracted the buffer access. None of the numbers exceeded the proper bounds. It was close to bedtime so I finally gave up. I was tired. Then I realized it wouldn't be until the next evening when I could look at this again. So I got up again and started looking at the code again. I had a loop to check the output of my algo that I did the memory access of the buffer. It too was not fully filling my temp image to show how the algo was working. WTF!

Then I finally realized the flaw:

And my test loop to test the algo:

I kept overlooking the error because I was sure it was right. Also my asserts for the functions to access the buffers? They only checked the inputs x and y. So it didn't help that the math was wrong for reading and writing the buffers. It also worked fine on 128x128 images because the width and height were the same.

It is funny that I struggled with this part. The algo was actually surprisingly easy to formulate. I just looked through every point and checked a buffer to see if that point was used. If not then I would attempt to grow in the x and y direction the shaped of that point based upon pixel color. This was saved in a structure while growing that point. Then when that rectangle could not be grown further the inner loop would continue checking used points again.

I still have work to do to use the data this algo produces. I need to now figure out how to parent the rectangular areas to each other. I will probably use my check buffer to keep track of these rects by an index. Then do adjacent checks to determine parenting. Eventually I will have to extend this algo to 3 dimensions, but that should not be difficult.

Add Comment