Javascript利用canvas绘制两点间曲线和箭头
作者：相信神话2021
这篇文章主要为大家详细介绍了Javascript如何利用canvas实现在两点间绘制曲线和矩形,并且在矩形中绘制文字,感兴趣的小伙伴可以跟随小编一起学习一下
Javascript利用canvas，在两点间绘制曲线，矩形，并且在矩形中绘制文字，实现居中对齐，同时实现了箭头绘制，效果如图:
一、html代码
代码如下
<canvas id="canvas" width="1000" height="600"></canvas>
二、css代码
canvas {
display: block;
width: 1000px;
height: 600px;
background: conic-gradient(#eee 25%, white 0deg 50%, #eee 0deg 75%, white 0deg) 0 / 20px 20px;
margin-inline: auto;
}
@media (max-width: 640px) {
canvas {
width: 100vw;
height: 60vw;
}
}
三、Javascript代码
代码如下
var context = document.getElementById("canvas").getContext("2d"); ;
// 绘制尺寸
var width = canvas.width;
var height = canvas.height;
// 两个方块的坐标、尺寸，颜色等数据
var data = [{
x: 800,
y: 180,
width: 200,
height: 50,
color: 'deepskyblue',
text:"+u+ate"
}, {
x: 600,
y: 680,
width: 200,
height: 50,
color: 'deeppink',
text:"gress 迈步"
}];
// 绘制矩形方法
var drawRect = function () {
data.forEach(function (obj) {
context.beginPath();
context.fillStyle = obj.color;
context.fillRect(obj.x, obj.y, obj.width, obj.height);
context.closePath();
context.font="30px Verdana";
context.fillStyle="#fff";
console.log(context.measureText(obj.text))
const textMetrics = context.measureText(obj.text);
// 所有字在这个字体下的高度
let fontHeight = textMetrics.fontBoundingBoxAscent + textMetrics.fontBoundingBoxDescent;
console.log(fontHeight)
context.fillText(obj.text,0,0)
context.fillText(obj.text,obj.x+(obj.width-context.measureText(obj.text).width)/2,obj.y+fontHeight);
});
};
// 绘制连接曲线方法
var drawCurve = function () {
// 按照坐标位置排序
var dataSort = data.sort(function (objA, objB) {
return (objA.y + objA.height) - (objB.y + objB.height);
});
// 知道上下数据
var from = dataSort[0];
var to = dataSort[1];
// 曲线的起点终点
var fromX = from.x + from.width / 2;
var fromY = from.y + from.height;
var toX = to.x + to.width / 2;
var toY = to.y;
// 曲线控制点坐标
var cp1x = fromX;
var cp1y = fromY + (toY - fromY) / 2;
var cp2x = toX;
var cp2y = toY - (toY - fromY) / 2;
// 开始绘制曲线
context.beginPath();
context.lineWidth = 1
context.strokeStyle = '#000';
context.moveTo(fromX, fromY);
// 绘制曲线点
context.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, toX, toY);
context.stroke();
};
// 绘制方法
var draw = function () {
context.clearRect(0, 0, width, height);
drawRect();
drawCurve();
};
draw();
canvas_arrow(ctx, 10, 30, 200, 150);
canvas_arrow(ctx, 100, 200, 400, 50);
canvas_arrow(ctx, 200, 30, 10, 150);
canvas_arrow(ctx, 400, 200, 100, 50);
ctx.stroke();
function canvas_arrow(context, fromx, fromy, tox, toy) {
var headlen = 10; // length of head in pixels
var dx = tox - fromx;
var dy = toy - fromy;
var angle = Math.atan2(dy, dx);
context.moveTo(fromx, fromy);
context.lineTo(tox, toy);
context.lineTo(tox - headlen * Math.cos(angle - Math.PI / 6), toy - headlen * Math.sin(angle - Math.PI / 6));
context.moveTo(tox, toy);
context.lineTo(tox - headlen * Math.cos(angle + Math.PI / 6), toy - headlen * Math.sin(angle + Math.PI / 6));
}
ok，代码就是如此
完整代码
<!DOCTYPE HTML>
<html>
<head>
<style>
canvas {
display: block;
width: 1000px;
height: 600px;
background: conic-gradient(#eee 25%, white 0deg 50%, #eee 0deg 75%, white 0deg) 0 / 20px 20px;
margin-inline: auto;
}
@media (max-width: 640px) {
canvas {
width: 100vw;
height: 60vw;
}
}
</style>
</head>
<body>
<canvas id="canvas" width="2000" height="1200"></canvas>
<script>
var context = document.getElementById("canvas").getContext("2d"); ;
// 绘制尺寸
var width = canvas.width;
var height = canvas.height;
// 两个方块的坐标、尺寸，颜色等数据
var data = [{
x: 800,
y: 180,
width: 200,
height: 50,
color: 'deepskyblue',
text:"+u+ate"
}, {
x: 600,
y: 680,
width: 200,
height: 50,
color: 'deeppink',
text:"gress 迈步"
}];
// 绘制矩形方法
var drawRect = function () {
data.forEach(function (obj) {
context.beginPath();
context.fillStyle = obj.color;
context.fillRect(obj.x, obj.y, obj.width, obj.height);
context.closePath();
context.font="30px Verdana";
context.fillStyle="#fff";
console.log(context.measureText(obj.text))
const textMetrics = context.measureText(obj.text);
// 所有字在这个字体下的高度
let fontHeight = textMetrics.fontBoundingBoxAscent + textMetrics.fontBoundingBoxDescent;
console.log(fontHeight)
context.fillText(obj.text,0,0)
context.fillText(obj.text,obj.x+(obj.width-context.measureText(obj.text).width)/2,obj.y+fontHeight);
});
};
// 绘制连接曲线方法
var drawCurve = function () {
// 按照坐标位置排序
var dataSort = data.sort(function (objA, objB) {
return (objA.y + objA.height) - (objB.y + objB.height);
});
// 知道上下数据
var from = dataSort[0];
var to = dataSort[1];
// 曲线的起点终点
var fromX = from.x + from.width / 2;
var fromY = from.y + from.height;
var toX = to.x + to.width / 2;
var toY = to.y;
// 曲线控制点坐标
var cp1x = fromX;
var cp1y = fromY + (toY - fromY) / 2;
var cp2x = toX;
var cp2y = toY - (toY - fromY) / 2;
// 开始绘制曲线
context.beginPath();
context.lineWidth = 1
context.strokeStyle = '#000';
context.moveTo(fromX, fromY);
// 绘制曲线点
context.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, toX, toY);
context.stroke();
};
// 绘制方法
var draw = function () {
context.clearRect(0, 0, width, height);
drawRect();
drawCurve();
};
draw();
canvas_arrow(ctx, 10, 30, 200, 150);
canvas_arrow(ctx, 100, 200, 400, 50);
canvas_arrow(ctx, 200, 30, 10, 150);
canvas_arrow(ctx, 400, 200, 100, 50);
ctx.stroke();
function canvas_arrow(context, fromx, fromy, tox, toy) {
var headlen = 10; // length of head in pixels
var dx = tox - fromx;
var dy = toy - fromy;
var angle = Math.atan2(dy, dx);
context.moveTo(fromx, fromy);
context.lineTo(tox, toy);
context.lineTo(tox - headlen * Math.cos(angle - Math.PI / 6), toy - headlen * Math.sin(angle - Math.PI / 6));
context.moveTo(tox, toy);
context.lineTo(tox - headlen * Math.cos(angle + Math.PI / 6), toy - headlen * Math.sin(angle + Math.PI / 6));
}
</script>
</body>
</html>
到此这篇关于Javascript利用canvas绘制两点间曲线和箭头的文章就介绍到这了,更多相关Javascript canvas内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！