Bilinear Up/Downsampling: Pixel Grid Alignment and That Infamous GPU Half-Pixel Offset
2025-01-27
This article delves into the common misconceptions and pitfalls surrounding bilinear up/downsampling techniques. The author points out that bilinear up/downsampling isn't a single concept; its definition and implementation vary, leading to long-standing bugs and confusion, even affecting top libraries like TensorFlow. The article thoroughly explains pixel grid alignment, GPU half-pixel offsets, and the role of odd/even filters. Using a signal processing perspective, it analyzes operations like zero-insertion and post-filtering, ultimately concluding that choosing the right coordinate system and filter is crucial for obtaining correct results.
Development
signal processing