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 :
紫苏是我国传统的药食同源植物，具有悠久的历史文化价值。在《诗经》《尔雅》等古代典籍中，紫苏被称为“荏”“桂荏”“荏苒”等，后来被收录于《名医别录》《本草纲目》等药学著作。
。业内人士推荐雷电模拟器官方版本下载作为进阶阅读
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