GPU 实时像素排序

For each row of the image, mark span boundaries wherever luminance crosses a lower or upper threshold, so only mid-brightness runs get sorted. Load each row into workgroup shared memory in a compute shader and run a bitonic sorting network over it, comparing keys only within the same span (using span id as the high bits of the sort key). Write the sorted pixels back and repeat per frame for video input. Expose threshold and sort direction (rotate the image before and after) as controls.