At quality 80-85 the difference is invisible at normal viewing distance and the file typically drops by 60-80%. The catch is that it is one-way: re-saving the JPG repeatedly compounds the artefacts each time. Keep the ICO as the master and regenerate the JPG from it whenever you need a new size. ICO 允许一个文件服务于任务栏、文件列表、桌面快捷键和浏览器标签, 而不让其中任何一个看到重新复制的标签 。 JPG 丢失: 图像转换为 DCT, 量化和加密, 质量控制了丢弃多少 。