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canvas learning 3---drawing coordinate system
- 坏嘻嘻Original
- 2018-09-14 09:49:251786browse
Whether you are a newbie or an experienced user, this tutorial is worth reading.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>网格</title>
<style>
#c1{
border:1px solid black;
}
</style>
<script>
window.onload = function(){
var oCanvas = document.getElementById('c1')
var gd = oCanvas.getContext('2d')
// 你要画一个表格：
// 你得思考，每个格子多大！
var space = 20
// 1, 得到 画布的宽和高
var cWidth = gd.canvas.width;
var cHeight = gd.canvas.height;
// 当你记不住api 的时候，就打印出来看看！
var lines = Math.floor(cHeight/space)
var cols = Math.floor(cWidth/space)
for(let i = 0;i<lines;i++){
gd.beginPath()
gd.moveTo(0,space*i-0.5)
gd.lineTo(cWidth,space*i-0.5)
gd.strokeStyle='#aaa'
gd.stroke();
}
// 画第二个竖着的格子！
for(let j = 0; j<cols;j++){
gd.beginPath();
gd.moveTo(space*j-0.5,0)
gd.lineTo(space*j-0.5,cHeight)
gd.strokeStyle="#aaa"
gd.stroke()
}
// 下面是画那个坐标！
// 1, everPadding（坐标离 网格边界的上下左右的距离！）
var everPadding = 40
// 起点(坐标原点)
var x0 = everPadding;
var yo = cHeight -everPadding
// x 轴，终点：
var x1 = cWidth-everPadding;
// 竖着方向：
// 画着再说：
gd.beginPath();
gd.moveTo(x0,yo)
gd.lineTo(x1,yo)
gd.lineTo(x1-space,yo-space)
gd.lineTo(x1-space,yo+space)
gd.lineTo(x1,yo)
gd.strokeStyle="red"
gd.fillStyle="red"
gd.stroke()
gd.fill()
gd.beginPath()
gd.moveTo(x0,yo)
gd.lineTo(x0,everPadding)
gd.lineTo(x0-space,everPadding+space)
gd.lineTo(x0+space,everPadding+space)
gd.lineTo(x0,everPadding)
gd.strokeStyle="red"
gd.fillStyle="red"
gd.stroke()
gd.fill()
}
</script>
</head>
<body>
<canvas id="c1" width="500" height="500"></canvas>
</body>
</html>Display:
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