在微信上给用户修改头像的时候，用canvas来截图。结果报错：Owechat_login.js:226 Uncaught TypeError: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The provided double value is non-finite.
代码：
function cropImage(targetCanvas, x, y, width, height) {

        var targetctx = targetCanvas.getContext('2d');
        var targetctxImageData = targetctx.getImageData(x, y, width, height); // sx, sy, sWidth, sHeight
    
        var c = document.createElement('canvas');
        var ctx = c.getContext('2d');
    
        c.width = width;
        c.height = height;
    
        ctx.rect(0, 0, width, height);
        ctx.fillStyle = 'white';
        ctx.fill();
        ctx.putImageData(targetctxImageData, 0, 0); // imageData, dx, dy
    
        document.getElementById('image').src = c.toDataURL('image/jpeg', 0.92);
        document.getElementById('image').style.display = 'initial';
    }