在单个HTML页面中绘制多个HTML Canvas元素

Question

我有一个html页面,我需要在其中添加多个canvas元素并在页面加载时加载它.

function draw()
{
var c=document.getElementById("myCanvas");
var padding = 20;
var ctx=c.getContext("2d");
var grd=ctx.createLinearGradient(0,0,175,50);
grd.addColorStop(0,"#E05D1B");
grd.addColorStop(1,"#00FF00");
ctx.fillStyle=grd;
ctx.fillRect(0,0,275,50);
}

<canvas id="myCanvas" width="250" height="8" style="margin-bottom:10px;margin-left:10px;">
<img src="images\gradient1.png" style="margin-bottom:10px;margin-left:10px;"/>
</canvas>

我添加像这个代码与不同的ID,但我需要重新编码的JavaScript; 我怎么能减少它？

<canvas id="myCanvas1" width="250" height="8" style="margin-bottom:10px;margin-left:10px;"> <img src="images\gradient1.png" style="margin-bottom:10px;margin-left:10px;"/> </canvas>

Answer 1

您可以将单独的canvas元素的上下文作为参数传递给draw函数(小提琴):

function draw(ctx)
{
    var grd=ctx.createLinearGradient(0,0,175,50);
    grd.addColorStop(0,"#E05D1B");
    grd.addColorStop(1,"#00FF00");
    ctx.fillStyle=grd;
    ctx.fillRect(0,0,275,50);
}

draw(document.getElementById("canvas_1").getContext("2d"));
draw(document.getElementById("canvas_2").getContext("2d"));

或者,根据您拥有的画布元素数量,在循环(小提琴)上调用绘图函数可能更有效:

function draw(ctx)
{
    var grd=ctx.createLinearGradient(0,0,175,50);
    grd.addColorStop(0,"#E05D1B");
    grd.addColorStop(1,"#00FF00");
    ctx.fillStyle=grd;
    ctx.fillRect(0,0,275,50);
}

var i = 1;
while (document.getElementById("canvas_" + i)) {
   draw(document.getElementById("canvas_" + i).getContext("2d"));
   i ++;       
}