未在web-worker中加载SVG图像

Question

我正在尝试在web-worker中运行此typescript代码：

   async BuildImage(): Promise<void> {

    let data1 = `<svg xmlns='http://www.w3.org/2000/svg' width='50' height='50'>
                    <foreignObject width='100%' height='100%' style="background:blue">
                      <div xmlns='http://www.w3.org/1999/xhtml' style='font-size:12px'>                        
                        <ellipse cx="23" cy="23" rx="25" ry="25" style="fill:yellow;stroke:purple;stroke-width:2" />
                      </div>
                    </foreignObject>
                  </svg>`;

    let svg = new Blob([data1], { type: "image/svg+xml;charset=utf-8" });
    var image = await createImageBitmap(svg);

}

但是抛出了带有"InvalidStateError"的"The source image could not be decoded."

​

我也尝试过这个代码：

   async BuildImage(): Promise<void> {

    let data1 = `<svg xmlns='http://www.w3.org/2000/svg' width='50' height='50'>
                    <foreignObject width='100%' height='100%' style="background:blue">
                      <div xmlns='http://www.w3.org/1999/xhtml' style='font-size:12px'>                        
                        <ellipse cx="23" cy="23" rx="25" ry="25" style="fill:yellow;stroke:purple;stroke-width:2" />
                      </div>
                    </foreignObject>
                  </svg>`;

    let svg = new Blob([data1], { type: "image/svg+xml;charset=utf-8" });
    let url = URL.createObjectURL(svg);

    var loadImageAsync = new Promise<HTMLImageElement>(resolve => {

        let img = new Image();
        img.onload = () => resolve(img);
        img.onerror = () => resolve(img);

        img.src = url;
    });

    this.image = await loadImageAsync;}

但现在的问题是，new Image()对象没有在web-worker中定义，因为它不能访问DOM。然而，最后一种方法在非web-worker场景中有效，但createImageBitmap在任何地方都不起作用。

有谁知道如何在web-worker或任何解决方案中从SVG构建和镜像这种情况？

谢谢

Answer 1

由于他们还没有实现该规范，

目前可能的解决方法是在主线程中从svg字符串生成一个图像，然后将生成的图像位图发送回您的worker。

所以在你的主线程代码中

// Loads the SVG image asynchronously
function loadSVGAsync(svgString) 
 return new Promise(resolve => {
  const img = new Image();
  img.onload = function () {
    resolve(this);
  };
  img.src = 'data:image/svg+xml;charset=utf8,' + encodeURIComponent(svgString);
 });
}

const worker = new Worker('...');

worker.addEventListener('message', async ev => {
 const YourSvgString = '...';

 const img = await loadSVGAsync(YourSvgString);

 // Pass over the image Bit map to your worker
 worker.postMessage({svg: await createImageBitMap(img)});
});

在您的worker中

self.addEventListener('message', (ev) => {
  // Do whatever you need with the image
  const svgImage = ev.data.svg;
});