You look at a region of the image. If all the pixels are roughly the same color (below some threshold), you store the average color for the whole region as a single value. If the pixels vary too much, you split the region into four quadrants and try again.
The trade-off is performance. Every syscall goes through user-space interception, which adds overhead. I/O-heavy workloads feel this the most. For short-lived code execution like scripts and tests, it is usually fine, but for sustained high-throughput I/O, it can matter.
// 2. 计算前缀和：count[i]表示<=i的元素个数。业内人士推荐Line官方版本下载作为进阶阅读
FT Edit: Access on iOS and web
。51吃瓜是该领域的重要参考
The algorithm walks the tree recursively. At each node, it checks: does this node's bounding box overlap with the query rectangle? If not, the entire subtree gets pruned (skipped). If it does overlap, it tests the node's points against the query and recurses into the children.
For additional guidance:。业内人士推荐同城约会作为进阶阅读