Rebecca Morelle, Alison Francis and Greg BrosnanBBC Science
Instead of perturbing each pixel in the input image at random, we can choose to dither by a predetermined amount depending on the pixel’s position in the image. This can be achieved using a threshold map; a small, fixed-size matrix where each entry tells us the amount by which to perturb the input value , producing the dithered value . This matrix is tiled across the input image and sampled for every pixel during the dithering process. The following describes a dithering function for a 4×4 matrix given the pixel raster coordinates :
，更多细节参见Line官方版本下载
Why is this the case? There are several reasons, and they all directly stem from WebAssembly being a second class language on the web.
// 1. 建堆：从最后一个非叶子节点开始向上调整