HTML5 Canvas自定義圓角矩形與虛線示例代碼

2020-03-24 16:40:18

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HTML5 Canvas自定義圓角矩形與虛線(RoundedRectangle and Dash Line)

實(shí)現(xiàn)向HTML Canvas 2d context繪制對(duì)象中添加自定義的函數(shù)功能演示，如何繪制虛線以及控制虛線間隔大小，學(xué)會(huì)繪制圓角矩形的技巧。

HTML5 Canvas繪制對(duì)象中提供的原生功能沒(méi)有實(shí)現(xiàn)繪制圓角矩形與虛線的功能，但是通過(guò)JavaScript語(yǔ)言的Object.prototype可以實(shí)現(xiàn)對(duì)對(duì)象CanvasRenderingContext2D添加這兩個(gè)函數(shù)功能。代碼的演示效果如下：

組件fishcomponent.js的代碼如下：

復(fù)制代碼代碼如下:
CanvasRenderingContext2D.prototype.roundRect =
function(x, y, width, height, radius, fill, stroke) {
if (typeof stroke == "undefined") {
stroke = true;
}
if (typeof radius === "undefined") {
radius = 5;
}
this.beginPath();
this.moveTo(x + radius, y);
this.lineTo(x + width - radius, y);
this.quadraticCurveTo(x + width, y, x + width, y + radius);
this.lineTo(x + width, y + height - radius);
this.quadraticCurveTo(x + width, y + height, x + width - radius, y+ height);
this.lineTo(x + radius, y + height);
this.quadraticCurveTo(x, y + height, x, y + height - radius);
this.lineTo(x, y + radius);
this.quadraticCurveTo(x, y, x + radius, y);
this.closePath();
if (stroke) {
this.stroke();
}
if (fill) {
this.fill();
}
};
CanvasRenderingContext2D.prototype.dashedLineTo = function (fromX, fromY, toX, toY, pattern) {
// default interval distance - 5px
if (typeof pattern === "undefined") {
pattern = 5;
}
// calculate the delta x and delta y
var dx = (toX - fromX);
var dy = (toY - fromY);
var distance = Math.floor(Math.sqrt(dx*dx + dy*dy));
var dashlineInteveral = (pattern = 0) ? distance : (distance/pattern);
var deltay = (dy/distance) * pattern;
var deltax = (dx/distance) * pattern;
// draw dash line
this.beginPath();
for(var dl=0; dl dashlineInteveral; dl++) {
if(dl%2) {
this.lineTo(fromX + dl*deltax, fromY + dl*deltay);
} else {
this.moveTo(fromX + dl*deltax, fromY + dl*deltay);
}
}
this.stroke();
};

HTML中調(diào)用演示：

復(fù)制代碼代碼如下:
!DOCTYPE html
html
head
meta http-equiv="X-UA-Compatible" content="chrome=IE8"
meta http-equiv="Content-type" content="text/html;charset=UTF-8"
title Canvas Rounded Rectangle Demo /title
script src="fishcomponent.js" /script
link href="default.css" rel="stylesheet" /
script
var ctx = null; // global variable 2d context
var imageTexture = null;
window.onload = function() {
var canvas = document.getElementById("text_canvas");
console.log(canvas.parentNode.clientWidth);
canvas.width = canvas.parentNode.clientWidth;
canvas.height = canvas.parentNode.clientHeight;
if (!canvas.getContext) {
console.log("Canvas not supported. Please install a HTML5 compatible browser.");
return;
}
var context = canvas.getContext('2d');
context.stroke ;
context.fill ;
context.roundRect(50, 50, 150, 150, 5, true);
context.stroke ;
for(var i=0; i i++) {
var delta = i*20;
var pattern = i*2+1;
context.dashedLineTo(250, 50+delta, 550, 50+delta, pattern);
}
}
/script
/head
body
h1 HTML5 Canvas Dash-line Demo - By Gloomy Fish /h1
pre Dash line and Rounded Rectangle /pre
div id="box_plot"
canvas id="text_canvas" /canvas
/div
/body
/html
html教程

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