问题描述
将颜色值从浮点数转换为字节的正确方法是什么?起初我认为 b=f*255.0 应该这样做，但现在我在想，在这种情况下，只有确切的 1.0 会被转换为 255，但 0.9999 已经是 254 这可能不是我想要的...
What would be the correct way of converting color value from float to byte? At first I thought b=f*255.0 should do it, but now I'm thinking, that in this case only the exact 1.0 will be converted to 255, but 0.9999 will already be 254 which is probably not what I want...
看起来 b=f*256.0 会更好，除了在精确的 1.0 的情况下它会产生 256代码>.
It seems that b=f*256.0 would be better except that it would have an unwanted case of making 256 in the case of exact 1.0.
最后我使用了这个:
#define F2B(f) ((f) >= 1.0 ? 255 : (int)((f)*256.0))
推荐答案
1.0 是唯一可能出错的情况，所以单独处理:
1.0 is the only case that can go wrong, so handle that case separately:
b = floor(f >= 1.0 ? 255 : f * 256.0)
此外，为了避免由于舍入误差(例如 f=1.0000001)导致的错误行为，强制 f 确实是 0
Also, it might be worth forcing that f really is 0<=f<=1 to avoid incorrect behaviour due to rounding errors (eg. f=1.0000001).
f2 = max(0.0, min(1.0, f))
b = floor(f2 == 1.0 ? 255 : f2 * 256.0)
替代安全解决方案:
b = (f >= 1.0 ? 255 : (f <= 0.0 ? 0 : (int)floor(f * 256.0)))
或
b = max(0, min(255, (int)floor(f * 256.0)))
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