<canvas id="myCanvas" width="300" height="150" style="border:1px solid #d3d3d3;">

您的浏览器不支持 HTML5 canvas 标签。

</canvas>

<script>

var c=document.getElementById("myCanvas");

var ctx=c.getContext("2d");

ctx.fillStyle="red";

ctx.fillRect(10,10,50,50);

var imgData=ctx.getImageData(30,30,50,50);

red=imgData.data[0];

green=imgData.data[1];

blue=imgData.data[2];

alpha=imgData.data[3];

alert(red + " " + green + " " + blue + " " + alpha);

</script>

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