img srcset 和尺寸无法正常工作

问题描述

我目前正在尝试在我的网站上制作更好的响应式图片.经过一番研究，我发现了 srcset 和 sizes 属性.

I am currently trying to make better responsive images on my site. After some research I found the the srcset and sizes attributes.

我的目标如下:

• 当屏幕尺寸大于 600 像素或小于 300 像素时，我想提供 250x250 的图片
• 当它介于这两个值之间时，我想提供 350x350 的图像
• 此外，我希望为具有更高像素比的屏幕提供更高分辨率的图像

这是我想出来的.但它不像我想的那样工作.始终提供 250x250 的小型广告.

This is what I came up with. But it is not working as I though it would. The small 250x250 is always being served.

<img src="https://placehold.it/250"
  srcset="https://placehold.it/700 700w, https://placehold.it/500 500w, https://placehold.it/350 350w, https://placehold.it/250 250w"
   sizes="((max-width: 600px) and (min-width: 300px) and (min-resolution: 2)) 350px, (min-resolution: 2) 250px, ((max-width: 600px) and (min-width: 300px)) 350px, 250px" />

我还有一个问题:
在我的测试中，我发现当调整窗口大小时浏览器不会加载新图像，因此应该提供不同的图像.可以这样做吗?

And I have one additional question:
In my tests I found out that the browser won't load new images when the window is resized so that a different image should be served. Is it possible to do that?

推荐答案

好的.经过一番细致的研究，我发现我没有正确理解 sizes 属性.

Ok. After some tidious research I found out that I did not understand the sizes-attribute correctly.

以下是我如何实现我想要的:

The following is how I can achieve what I want:

<img src="https://placehold.it/250"
  srcset="https://placehold.it/700 700w, https://placehold.it/500 500w, https://placehold.it/350 350w, https://placehold.it/250 250w"
   sizes="(max-width: 600px) calc(100vw - 50px), 250px" />

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