Quality issues for animated images

Description

My code includes the setting of this limitation:

/// Limits scale down to 24MB.
SDImageCoderHelper.defaultScaleDownLimitBytes = 24 * 1_024 * 1_024

When I get an animated image data that weighs 1.8 MB, the quality is severely degraded, and if I saw correctly my final image was 0.5 MB. I tried to play around with setting the value and in the end I got an image of 7200 bytes with the 1 MB limit set.

This was strange to me, so I tried exploring the codebase and seemed to find the problem in this line: https://github.com/SDWebImage/SDWebImageWebPCoder/pull/75/files#diff-e9c046b25a4d1b5fd2e490c2ebc802f1a63ef0459e0ad74dd3647f72d9c68323R94

Am I misunderstanding the expected behavior? Because it looks like a bug to me. Since it is strange that by setting the limit to 24 MB I get image quality degradation and image size reduction when its image data size is only 1.77 MB.

Also maybe you can tell me why when I try to download a heavy image and several small images, if the heavy image was added earlier, I don't get a response for the small images until the large one is downloaded? (It is important to note that I am considering the case of downloading an image from disk or over the network, only in these cases this happens).

从 SDImageCoderHelper.defaultScaleDownLimitBytes 开始，并检查引用行中链接的 SDWebImageWebPCoder pull request。使用指定的限制重现动画图像的质量和大小行为，然后分别调查磁盘或网络下载的顺序。当观察到的行为得到解释，并且所有已确认的回归都有针对性的测试时，即表示完成。