Canvas案例-实现ECG心电图
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描绘一个ECG心电图
上代码:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>canvas绘制心电图</title>
</head>
<body>
<canvas id="ecg" width="751" height="201" ></canvas>
</body>
</html>
<script>
var ecgDom = document.getElementById('ecg');
var ecgDomWidth = ecgDom.width - 1,
ecgDomHeight = ecgDom.height - 21;
var addX = ecgDomWidth / 50, // 这个50是横坐标总的中格子数
addY = ecgDomHeight / 12, // 这个12是纵坐标总的中格子数
marginL = 0.5;
/*
1、context.strokeRect(x,y,width,height); strokeRect() 方法绘制矩形（不填色）。笔触的默认颜色是黑色。
*/
// canvas 的左上角坐标为 (0,0)
// 绘制表格的函数，此表格包含大中小三种格子，分别对应三种函数：
function drawSmallGrid(c_canvas){ // 绘制小格子
var context = c_canvas.getContext("2d");
context.fillStyle = '#ff6b64';
var dotMarginX = addX / 5,
dotMarginY = addY / 5;
var i = dotMarginX;
// let num = 0;
for (i; i < ecgDomWidth; i += dotMarginX) {
// console.log(i);
// if ((i % addX) === 0) { console.log(i); }
if ((i % addX) !== 0) { // 列分隔线处不打点
for (var j = dotMarginY; j < ecgDomHeight; j += dotMarginY) {
if ((j % addY) !== 0) { // 行分割线处不打点
console.log('行分割线处不打点', j);
// num++;
// context.rect(x,y,width,height); 矩形左上角的 x 坐标, 矩形左上角的 y 坐标, 矩形的宽度，以像素计, 矩形的高度，以像素计
context.rect(i, j, 1, 0.5);
}
}
}
}
context.fill();
}
function drawMediumGrid(c_canvas){ // 绘制中格子
var context = c_canvas.getContext("2d");
context.strokeStyle = "#ff6b64";
context.strokeWidth=1.5;
context.setLineDash([3, 3]);
context.beginPath();
let num = 0;
for (var x = marginL; x < ecgDomWidth; x += addX) {
context.moveTo(x, 0); // moveTo(x,y) 定义线条开始坐标, Y轴的话从0开始描绘
context.lineTo(x, ecgDomHeight); // lineTo(x,y) 定义线条结束坐标, X轴可以描绘到1000
context.stroke();
num++;
};
console.log('X轴网格数:', num);
for (var y = marginL; y < ecgDomHeight; y += addY) {
context.moveTo(0, y);
context.lineTo(ecgDomWidth, y);
context.stroke();
};
context.closePath();
return;
}
function drawBigGrid(c_canvas){ // 绘制大格子
var context = c_canvas.getContext("2d");
context.strokeStyle = "#ff6b64"; // 设置或返回用于笔触的颜色、渐变或模式。
context.strokeWidth=1.5;
context.setLineDash([3, 3]); // 设置线条虚线样式的间距和长度。[3, 0]: 虚线长度为0则绘制成实线
context.beginPath(); // 起始一条路径，或重置当前路径.
var bigAddX = ecgDomWidth / 10, // 10表示10s
bigAddY = ecgDomHeight / 2; // 2表示把Y轴分成2份，分别为正负
for (var x = marginL; x < ecgDomWidth; x += bigAddX) {
context.moveTo(x, 0); // moveTo(x,y) 定义线条开始坐标
context.lineTo(x, ecgDomHeight); // lineTo(x,y) 定义线条结束坐标
context.stroke(); // stroke() 方法来绘制线条
};
for (var y = marginL; y < ecgDomHeight; y += bigAddY) {
context.moveTo(0, y); // moveTo(x,y) 定义线条开始坐标
context.lineTo(ecgDomWidth, y); // lineTo(x,y) 定义线条结束坐标
context.stroke(); // stroke() 方法来绘制线条
};
context.closePath(); // 关闭一条打开的子路径
return;
}
function drawBigBorder(c_canvas){ // 绘制边框
var context = c_canvas.getContext("2d");
/* context.strokeStyle = "#ff6b64"; // 设置或返回用于笔触的颜色、渐变或模式。
context.strokeWidth=1.5;
context.setLineDash([3, 3]); // 设置线条虚线样式的间距和长度。[3, 0]: 虚线长度为0则绘制成实线
context.beginPath(); // 起始一条路径，或重置当前路径.
context.moveTo(ecgDomWidth,0);
context.lineTo(ecgDomWidth,ecgDomHeight);
context.moveTo(0,ecgDomHeight);
context.lineTo(ecgDomWidth,ecgDomHeight);
context.closePath(); // 关闭一条打开的子路径 */
context.strokeStyle = "#ff6b64";
context.strokeWidth=1.5;
context.setLineDash([3, 3]);
context.beginPath();
context.moveTo(ecgDomWidth + marginL,0);
context.lineTo(ecgDomWidth + marginL,ecgDomHeight + 1);
context.moveTo(0,ecgDomHeight+marginL);
context.lineTo(ecgDomWidth,ecgDomHeight+marginL);
console.log('宽高:', ecgDomWidth, ecgDomHeight);
context.stroke();
return;
}
function drawBigBG(c_canvas){ // 绘制背景
var context = c_canvas.getContext("2d");
context.fillStyle = '#FFE9E9';
context.fillRect(0, 0, ecgDomWidth + 21, ecgDomHeight + 21);
}
function drawLabelX(c_canvas){ // 绘制横坐标的label
var secondLabel = ecgDomWidth / 10;
var context = c_canvas.getContext("2d");
context.strokeStyle = '#000';
context.setLineDash([3, 0]); // 设置线条虚线样式的间距和长度。[3, 0]: 虚线长度为0则绘制成实线
context.beginPath(); // 起始一条路径，或重置当前路径
context.strokeWidth=1.5;
for (var x = marginL; x <= ecgDomWidth + secondLabel; x += secondLabel) {
context.moveTo(x, ecgDomHeight); // moveTo(x,y) 定义线条开始坐标
context.lineTo(x, ecgDomHeight + secondLabel + 20); // lineTo(x,y) 定义线条结束坐标
context.stroke(); // stroke() 方法来绘制线条
};
// 绘制底部长线
context.moveTo(0, ecgDomHeight+marginL+20); // moveTo(x,y) 定义线条开始坐标
context.lineTo(ecgDomWidth,ecgDomHeight+marginL+20); // lineTo(x,y) 定义线条结束坐标
context.stroke(); // stroke() 方法来绘制线条
var textNum = 0;
for (var x = marginL; x <= ecgDomWidth + secondLabel; x += secondLabel) {
context.font="12px Arial";
context.fillStyle = "#000";
context.fillText(textNum+"s",x+2, ecgDomHeight + 15);
textNum++;
console.log('textNum:', textNum);
};
context.closePath(); // 关闭一条打开的子路径
}
// 然后是绘制心电图的函数:
function drawLine(c_canvas) {
var ctx = c_canvas.getContext('2d');
ctx.strokeStyle = "#000"; // 设置或返回用于笔触的颜色、渐变或模式。
ctx.strokeWidth = 1;
ctx.setLineDash([3, 0]); // 设置线条虚线样式的间距和长度。[3, 0]: 虚线长度为0则绘制成实线
ctx.beginPath(); // 起始一条路径，或重置当前路径。
ctx.moveTo(0.5, 90); // moveTo(x,y) 定义线条开始坐标
ctx.lineTo(10, 90); // lineTo(x,y) 定义线条结束坐标
for(var x = 9; x < 90; x++) {
ctx.lineTo(x * 6, (Math.random() * 10 -5) * 10 + 90)
}
ctx.lineTo(650, 90)
ctx.lineTo(750, 90)
ctx.stroke(); // stroke() 方法来绘制线条
ctx.closePath(); // 关闭一条打开的子路径
}
// 最后一起调用这些函数：
(function draw(){
var c_canvas = document.getElementById("ecg");
var canvas = c_canvas.getContext("2d");
// c_canvas.fillStyle = "#ffe9e9";
// canvas.fillRect(0, 0, c_canvas.width, c_canvas.height)
drawBigBG(c_canvas);
drawSmallGrid(c_canvas);
drawMediumGrid(c_canvas)
drawBigGrid(c_canvas);
drawLine(c_canvas);
drawBigBorder(c_canvas);
drawLabelX(c_canvas);
return;
})();
</script>
效果图:
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