[GitHub] hcgit9527 commented on issue #9417: 请问echarts滚轮缩放时，如何同时缩放背景图片呢？求解答

[GitBox <gi...@apache.org>]

hcgit9527 commented on issue #9417: 请问echarts滚轮缩放时，如何同时缩放背景图片呢？求解答
URL: https://github.com/apache/incubator-echarts/issues/9417#issuecomment-439309479
 
 
   > ```
   >     //添加背景
   >     var img = new Image();
   >     var canvas = document.createElement('canvas');
   >     var ctx = canvas.getContext('2d');
   >     canvas.width = myChart.getWidth() * window.devicePixelRatio;
   >     canvas.height = myChart.getHeight() * window.devicePixelRatio;
   > 
   >     //背景
   >     var fullImage = new Image();
   >     var scale = 4.8;//初始缩放比例
   > 
   >     img.onload = function () {
   >         ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
   >         
   >         /////网格背景
   >         ctx.clearRect(0, 0, canvas.width, canvas.height);
   >         ctx.scale(scale, scale);
   >         ctx.strokeStyle = "#333";
   >         ctx.lineWidth = 0.1;
   >         ctx.translate(17, 25);
   >         var startx = -2 * scale;
   >         var starty = -2 * scale;
   >         var endcanvas = canvas.width + startx;
   >         var endheight = canvas.height + starty;
   >         for (var x = startx; x < endcanvas; x += 2 * scale) {
   >             for (var y = starty; y < endheight; y += 2 * scale) {
   >                 ctx.beginPath();
   >                 ctx.moveTo(x - 0.15 * scale, y);
   >                 ctx.lineTo(x + 0.15 * scale, y);
   >                 ctx.moveTo(x, y - 0.15 * scale);
   >                 ctx.lineTo(x, y + 0.15 * scale);
   >                 ctx.closePath();
   >                 ctx.stroke();
   >             }
   >         }
   > 
   >         fullImage.src = canvas.toDataURL();
   >         setTimeout(function () {
   >             myChart.resize();
   >         }, 100)
   >     };
   >     img.src = "jz.svg";
   > ```
   > 为图表画了网格背景 ，如何滚轮缩放数据层的时候 背景也缩放
   
   

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