1、jpg:有损压缩格式
靠损失图片本身的质量来减小图片的体积，
适用于颜色丰富的图像;(像素点组成的，像素点越多会越清晰 )
2、gif：无损压缩格式
靠损失图片的色彩数量来减小图片的体积，支持透明，支持动画，
适用于颜色数量较少的图像;
3、png:无损压缩格式
损失图片的色彩数量来减小图片的体积，支持透明，不支持动画，是fireworks的 源文件格式，
适用于颜色数量较少的图像;
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4、svg:可缩放矢量图形
svg 图像在放大或改变尺寸的情况下其图形质量不会有所损失，使用 XML 格式定义图形
与其他图像格式相比，使用 svg的优势在于：
- svg 可被非常多的工具读取和修改（比如记事本）
- svg 与 jpg 和 gif 图像比起来，尺寸更小，且可压缩性更强。
- svg 图像可在任何的分辨率下被高质量地打印
- svg 可在图像质量不下降的情况下被放大
- svg 图像中的文本是可选的，同时也是可搜索的（很适合制作地图）
- svg 文件是纯粹的 XML
当然我们可以将svg代码打包到 js 文件中，以减少http的请求次数
svg格式的图片可以通过阿里的 iconfont 图标库进行生成，或者使用在线工具将其他格式转svg格式。
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原文地址：https://www.cnblogs.com/wertantan/p/10134477.html