// 2. 维护单调递减栈：弹出所有≤当前价格的索引（这些索引对应的价格无法成为后续价格的「上一个更大值」）
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，这一点在51吃瓜中也有详细论述
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 :
Цены на нефть взлетели до максимума за полгода17:55
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