Fabric Js Image blend过滤并更改Image src问题

Question

当我在FabricJS中尝试更改图像时，src工作正常，但在向该图像添加过滤器（混合图像）后，更改src无法正常工作：

更改图片src代码：

function replaceImage(imgLink) {  
  fabric.Image.fromURL(imgLink, function(img) {
    var object = canvas.getActiveObject();
    object._element.src = imgLink;
    canvas.renderAll();
  });
}

添加过滤器代码：

   filter2 = new fabric.Image.filters.BlendImage({
      image: mainObject,
      mode: 'mask',
      alpha: 0.5
   });

  let object = canvas.getActiveObject(); 
  object.filters.push(filter2);
  object.applyFilters();
  canvas.renderAll();

Answer 1

使用imageObj#setSrc更改图像对象的来源。和BlendImage模式可用的选项是multiply, add, diff, screen, subtract, darken, lighten, overlay, exclusion, tint其中之一。

DEMO

var canvas = new fabric.Canvas('editorCanvas', {
  backgroundColor: 'white',
  width: 300,
  height: 300
});
var imageObject;
fabric.Image.fromURL('https://picsum.photos/200/200', function(img) {
  img.set({width:200,height:200,scaleX:1,scaleY:1})
  imageObject = img;
  canvas.add(img);
},{crossOrigin:'annonymous'});
var i=0;
function addFilter(){
   filter2 = new fabric.Image.filters.BlendImage({
      image: imageObject,
      mode: 'multiply',
      alpha: 0.5
   });
   
  imageObject.filters.push(filter2);
  imageObject.applyFilters();
  canvas.requestRenderAll();
}

function changeSrc(){
  var url = 'https://picsum.photos/200/200?random='+ ++i;
  imageObject.setSrc(url,function(){
    canvas.requestRenderAll();
  },{crossOrigin:'annonymous'})
}

canvas{
  border:1px solid;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/2.7.0/fabric.js"></script>
<button onclick='changeSrc()'>changeSrc</button>
<button onclick='addFilter()'>addFilter</button><br>
<canvas id="editorCanvas"></canvas>