stackblur-iter

A fast, iterative, correct approach to Stackblur, resulting in a very smooth and high-quality output, with no edge bleeding.

This crate implements a tweaked version of the Stackblur algorithm requiring radius * 2 + 2 elements of space rather than radius * 2 + 1, which is a small tradeoff for much-increased visual quality.

The algorithm is exposed as an iterator (StackBlur) that can wrap any other iterator that yields elements of StackBlurrable. The StackBlur will then yield elements blurred by the specified radius.

Benefits of this crate

Stackblur is essentially constant-time. Regardless of the radius, it always performs only 1 scan over the input iterator and outputs exactly the same amount of elements.

Additionally, it produces results that are comparable to slow and expensive Gaussian blurs. As opposed to box blur which uses a basic rolling average, Stackblur uses a weighted average where each output pixel is affected more strongly by the inputs that were closest to it.

Despite that, Stackblur does not perform much worse compared to naive box blurs, and is quite cheap compared to full Gaussian blurs, at least for the CPU. The implementation in this crate will most likely beat most unoptimized blurs you can find on crates.io, as well as some optimized ones, and it is extremely flexible and generic.

For a full explanation of the improvements made to the Stackblur algorithm, see the iter module.

https://user-images.githubusercontent.com/4723091/173788732-2e3e125e-f7b3-4e0f-8582-cc2c148ba437.mp4

(In the above video, stackblur-iter is the centered blur, whereas the full-width one is another stackblur crate.)

Comparison to the stackblur crate

stackblur suffers from edge bleeding and flexibility problems. For example, it can only operate on buffers of 32-bit integers, and expects them to be packed linear ARGB pixels. Additionally, it cannot operate on a 2D subslice of a buffer (like imgref allows for this crate), and it does not offer any streaming iterators or documentation. And it also only supports a blur radius of up to 255.

Usage

Aside from StackBlurrable and StackBlur which host their own documentation, there are helper functions like blur and blur_argb that can be used to interact with 2D image buffers, due to the fact that doing so manually involves unsafe code (if you want no-copy).

See the full documentation for more.