Expected Behavior

Running validator https://validator.w3.org on basic <picture> elements as per setup config should not result in errors.

Current Behavior

Currently when running validator on:

<picture class="lozad" style="display: block; min-height: 1rem" data-iesrc="images/thumbs/04.jpg" data-alt="">
    <source srcset="images/thumbs/04.jpg" media="(min-width: 1280px)">
   

SVG will very likely take a little longer to render than a base64-encoded raster image. And the Gaussian Blur applied to the simple SVG shapes created by Primitive is probably quite CPU intensive.

Let's run a series of performance tests, ideally on WPT, to compare LQIP raster image rendering performance vs. SQIP rendering performance and also compare CPU utilization.

Docker部署Lsky-Pro的方法

直接使用Docker Hub拉取使用

该镜像为自己维护的镜像，会每周拉取一次最新的代码进行构建，有问题可以在该仓库下发起issues

参考了之前 #256 里面的方法，对2.0正式版本也自己写了个Dockfile。在Dockerfile里面直接修改了PHP上传图片100M的限制，现在应该是可以开箱即用的。

示例：

docker run -it --name=lskypro -p 9080:80 -d halcyonazure/lsky-pro-docker:latest

通过Dockerfile自己编译镜像

该方法是参考了 #256 里面同样需要感谢的大哥的D

The value of allowed undershoot in the resize mode ExactOrSmaller is currently a compile time constant. It would be great to make this configurable for the developer using the library:

https://github.com/facebookincubator/spectrum/blob/fa9e917f5b062797d51c3e013aaa7d61926c72a5/cpp/spectrum/core/ResizeUtil.h#L22-L27