如何裁剪canvas.toDataURL

您好,
我想canvas.toDataURL()在将其发送到服务器之前裁剪我,但我没有找到如何:(
这是我的代码:

TakePhoto: function() {
        var myCanvas = document.getElementById('game');
        var dataURL = myCanvas.toDataURL();
        // crop the dataURL
    }

那么,如何裁剪dataURL？
谁能帮我 ？
提前致谢

该toDataURL方法将始终捕获整个画布.

因此,要捕获裁剪部分,您必须创建一个临时画布并将其大小调整为与裁剪相同的大小.

然后使用扩展形式drawImage来裁剪原始图像并将其绘制到临时画布上.

示例代码和演示:

var img=new Image();
img.crossOrigin='anonymous';
img.onload=start;
img.src="https://img.devbox.cn/3cccf/16086/243/3acb21bfbb644443.png";
function start(){
  var croppedURL=cropPlusExport(img,190,127,93,125);
  var cropImg=new Image();
  cropImg.src=croppedURL;
  document.body.appendChild(cropImg);
}

function cropPlusExport(img,cropX,cropY,cropWidth,cropHeight){
  // create a temporary canvas sized to the cropped size
  var canvas1=document.createElement('canvas');
  var ctx1=canvas1.getContext('2d');
  canvas1.width=cropWidth;
  canvas1.height=cropHeight;
  // use the extended from of drawImage to draw the
  // cropped area to the temp canvas
  ctx1.drawImage(img,cropX,cropY,cropWidth,cropHeight,0,0,cropWidth,cropHeight);
  // return the .toDataURL of the temp canvas
  return(canvas1.toDataURL());
}

body{ background-color: ivory; }
img{border:1px solid red; margin:0 auto; }

Original image

Cropped image create from cropping .toDataURL