Hello, a few notes below.
On Tue, Jun 17, 2008 at 10:49 AM, Nirav Patel <[EMAIL PROTECTED]> wrote: > As part of my project to add computer vision stuff to pygame, I'd like > to write a function or functions that do the following. > > For vision purposes, it would be very useful to have thresholding with > both upper and lower boundaries, returning both the number of pixels > within the threshold and the centroid of those pixels. This is a > trivial addition to the existing transform.threshold() function, but > is it acceptable to modify the input options and the output of an > existing function? Would it break compatibility with existing pygame > games? Would it make sense to have a second function so similar to an > existing one? > You could modify the existing function if the old functionality stays the same. Probably by adding another default argument. We try not to break existing functionality. I think the current one can use just one distance from the color. So it's both a lower, and upper threshold. I'm just wondering if it could be used already to do what you want? > The other function, which is also similar (and could even just be an > option in thresholding), is thresholding with connected component > detection. This would involve supplying an upper and lower threshold, > a Surface, and optionally a mask. The function would find the largest > blob of pixels in the Surface within the threshold, make a mask of > those pixels if desired, and return the centroid and number of pixels > in the blob. > Currently this can sort of be done by making a mask from the thresholded image. Mask has a get_bounding_rect() function. Doing the get_bounding_rect on a mask turns out to be fast because you process way less data -- as mask is 1 bit per pixel. Then you can sort the bounding rects on size to find the largest one. I'm not sure if that will be suitable for your task though, but I think maybe you could do things this way. > It could also be useful to have multiple connected component > detection, for "multi-touch" without having to use different colored > objects (or if you are using IR LEDs like the Wii does), but I'm not > sure how to handle that in a single pass of the array. Actually, I'm > not really sure how I'm going to handle both detection and creating a > mask in a single pass either. It may be necessary to store the > starting pixel, ending pixel, and size of each connected component on > the first pass, keeping track of which was the largest yet, and then > have a shorter second pass to create the mask that only starts at the > starting pixel and ends at the ending pixel. > Multiple areas can be found like above with Mask.get_bounding_rect(). Doing everything in one pass is hard... but if you reduce the data down -- by using a mask -- then the second pass can act on 32x less data. eg, a 1024x1024 image: >>>(1024 * 1024 * 4) / 32. 131072.0 So that is 4MB on the first pass down to 131KB of data to process on the second pass. > Any comments, reality checks, questions, or suggestions would be > greatly appreciated. > > Nirav >
