[js高手之路] html5 canvas教程 - 绘制七巧板

2022-02-25 01:00:30

七巧板长什么样？

用canvas把他画出来，其实就是把这7个区域的图形，每个点的坐标找出来，再用moveTo, lineTo连线，设置不同的颜色即可。

 <head>

     <meta charset='utf-8' />

     <style>

         #canvas {

             border: 1px dashed #aaa;

         }

     </style>

     <script>

         window.onload = function () {

             var oCanvas = document.querySelector("#canvas"),

                 oGc = oCanvas.getContext('2d'),

                 width = oCanvas.width, height = oCanvas.height,

                 tangram = [

                 { p: [{ x: 0, y: 0 }, { x: 800, y: 0 }, { x: 400, y: 400 }], color: "#caff67" }, //正上方绿色三角形区域

                 { p: [{ x: 0, y: 0 }, { x: 400, y: 400 }, { x: 0, y: 800 }], color: "#67becf" }, //左方蓝色三角形区域

                 { p: [{ x: 800, y: 0 }, { x: 800, y: 400 }, { x: 600, y: 600 }, { x: 600, y: 200 }], color: "#ef3d61" },

                 { p: [{ x: 600, y: 200 }, { x: 600, y: 600 }, { x: 400, y: 400 }], color: "#f9f51a" },

                 { p: [{ x: 400, y: 400 }, { x: 600, y: 600 }, { x: 400, y: 800 }, { x: 200, y: 600 }], color: "#a54c09" },

                 { p: [{ x: 200, y: 600 }, { x: 400, y: 800 }, { x: 0, y: 800 }], color: "#fa8ccc" },

                 { p: [{ x: 800, y: 400 }, { x: 800, y: 800 }, { x: 400, y: 800 }], color: "#f6ca29" }

             ];

             for (var i = 0; i < tangram.length; i++) {

                 draw( oGc, tangram[i]);

             };

             function draw( cxt, piece ) {

                 cxt.beginPath();

                 cxt.moveTo(piece.p[0].x, piece.p[0].y);

                 for (var i = 1; i < piece.p.length; i++) {

                     cxt.lineTo(piece.p[i].x, piece.p[i].y);

                 }

                 cxt.closePath();

                 cxt.fillStyle = piece.color;

                 cxt.fill();

             }

         }

     </script>

 </head>

 <body>

     <canvas id="canvas" width="800" height="800"></canvas>

 </body>

tangram存储了每个形状的顶点坐标与填充颜色，p就是每个区域的顶点组成的数组，数组中每个点用一个json对象存储.，一个有7个形状，tangram就是7项，然后用循环，把每个区域的顶点和其他的点用线连起来。注意每个区域的点一定要用路径，至于为什么？可以参考我的这篇文章：[js高手之路] html5 canvas系列教程 - 开始路径beginPath与关闭路径closePath详解

<head>
<meta charset='utf-8' />
<style>
#canvas {
border: 1px dashed #aaa;
}
</style>
<script>
window.onload = function () {
var oCanvas = document.querySelector("#canvas"),
oGc = oCanvas.getContext('2d'),
width = oCanvas.width, height = oCanvas.height,
tangram = [
{ p: [{ x: 0, y: 0 }, { x: 800, y: 0 }, { x: 400, y: 400 }], color: "#caff67" }, //正上方绿色三角形区域
{ p: [{ x: 0, y: 0 }, { x: 400, y: 400 }, { x: 0, y: 800 }], color: "#67becf" }, //左方蓝色三角形区域
{ p: [{ x: 800, y: 0 }, { x: 800, y: 400 }, { x: 600, y: 600 }, { x: 600, y: 200 }], color: "#ef3d61" },
{ p: [{ x: 600, y: 200 }, { x: 600, y: 600 }, { x: 400, y: 400 }], color: "#f9f51a" },
{ p: [{ x: 400, y: 400 }, { x: 600, y: 600 }, { x: 400, y: 800 }, { x: 200, y: 600 }], color: "#a54c09" },
{ p: [{ x: 200, y: 600 }, { x: 400, y: 800 }, { x: 0, y: 800 }], color: "#fa8ccc" },
{ p: [{ x: 800, y: 400 }, { x: 800, y: 800 }, { x: 400, y: 800 }], color: "#f6ca29" }
];
for (var i = 0; i < tangram.length; i++) {
draw( oGc, tangram[i]);
};
function draw( cxt, piece ) {
cxt.beginPath();
cxt.moveTo(piece.p[0].x, piece.p[0].y);
for (var i = 1; i < piece.p.length; i++) {
cxt.lineTo(piece.p[i].x, piece.p[i].y);
}
cxt.closePath();

cxt.fillStyle = piece.color;
cxt.fill();
}
}
</script>
</head>
<body>
<canvas id="canvas" width="800" height="800"></canvas>
</body>

run code

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