I've known some unhappy people in my life, been one at times.

我这辈子认识很多不幸福的人，我一度也不幸福。

An algorithm like this might start in the upper right corner, and check each pixel, one at time, calculating the difference from our target color.

像这样的算法可能从右上角开始，检查每个像素，一次一个，计算与目标颜色的差异。