在 HTML 画布中创建链接
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原文地址: http://stackoverflow.com/questions/6215841/
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Create links in HTML canvas
提问by Chris
Is it possible to create html links out of text that is rendered in a canvas element?
是否可以从画布元素中呈现的文本中创建 html 链接？
回答by dogbane
There is no easy way. You will have to draw the link text onto the canvas and then check for mouseclicks. Here is a demo html page:
没有简单的方法。您必须将链接文本绘制到画布上，然后检查鼠标点击。这是一个演示 html 页面：
<html>
<head>
<script type="text/javascript">
var canvas = document.getElementById("myCanvas");
var ctx;
var linkText="http://stackoverflow.com";
var linkX=5;
var linkY=15;
var linkHeight=10;
var linkWidth;
var inLink = false;
// draw the balls on the canvas
function draw(){
canvas = document.getElementById("myCanvas");
// check if supported
if(canvas.getContext){
ctx=canvas.getContext("2d");
//clear canvas
ctx.clearRect(0, 0, canvas.width, canvas.height);
//draw the link
ctx.font='10px sans-serif';
ctx.fillStyle = "#0000ff";
ctx.fillText(linkText,linkX,linkY);
linkWidth=ctx.measureText(linkText).width;
//add mouse listeners
canvas.addEventListener("mousemove", on_mousemove, false);
canvas.addEventListener("click", on_click, false);
}
}
//check if the mouse is over the link and change cursor style
function on_mousemove (ev) {
var x, y;
// Get the mouse position relative to the canvas element.
if (ev.layerX || ev.layerX == 0) { //for firefox
x = ev.layerX;
y = ev.layerY;
}
x-=canvas.offsetLeft;
y-=canvas.offsetTop;
//is the mouse over the link?
if(x>=linkX && x <= (linkX + linkWidth) && y<=linkY && y>= (linkY-linkHeight)){
document.body.style.cursor = "pointer";
inLink=true;
}
else{
document.body.style.cursor = "";
inLink=false;
}
}
//if the link has been clicked, go to link
function on_click(e) {
if (inLink) {
window.location = linkText;
}
}
</script>
</head>
<body onload="draw()">
<center>
<canvas id="myCanvas" width="200" height="200" style="border-style:solid;border-width:1px">Canvas not supported.</canvas>
</center>
</body>
</html>
回答by Yakovenko Max
This example shows how you can add multiple links to your HTML canvas:
此示例显示如何向 HTML 画布添加多个链接：
<!DOCTYPE html>
<!-- This page shows how to add multiple links to <canvas> (by Yakovenko Max) -->
<html>
<head>
<title>Canvas Links Example</title>
<script>
function OnLoad(){
// Get canvas
var canvas = document.getElementById("myCanvas");
// 2d context
var ctx = canvas.getContext("2d");
ctx.translate(0.5, 0.5); // * Move the canvas by 0.5px to fix blurring
// Block border
ctx.strokeStyle = "#5F7FA2";
ctx.strokeRect(50, 50, 185, 90);
// Photo
var img = new Image();
img.src = "http://www.cs.washington.edu/education/courses/csep576/05wi/projects/project4/web/artifact/liebling/average_face.gif";
img.onload = function(){
ctx.drawImage(img, 59.5, 59.5); // Use -0.5px on photos to prevent blurring caused by * fix
}
// Text
ctx.fillStyle = "#000000";
ctx.font = "15px Tahoma";
ctx.textBaseline = "top";
ctx.fillText("Username", 95, 65);
// ***** Magic starts here *****
// Links
var Links = new Array(); // Links information
var hoverLink = ""; // Href of the link which cursor points at
ctx.fillStyle = "#0000ff"; // Default blue link color
ctx.font = "15px Courier New"; // Monospace font for links
ctx.textBaseline = "top"; // Makes left top point a start point for rendering text
// Draw the link
function drawLink(x,y,href,title){
var linkTitle = title,
linkX = x,
linkY = y,
linkWidth = ctx.measureText(linkTitle).width,
linkHeight = parseInt(ctx.font); // Get lineheight out of fontsize
// Draw the link
ctx.fillText(linkTitle, linkX, linkY);
// Underline the link (you can delete this block)
ctx.beginPath();
ctx.moveTo(linkX, linkY + linkHeight);
ctx.lineTo(linkX + linkWidth, linkY + linkHeight);
ctx.lineWidth = 1;
ctx.strokeStyle = "#0000ff";
ctx.stroke();
// Add mouse listeners
canvas.addEventListener("mousemove", on_mousemove, false);
canvas.addEventListener("click", on_click, false);
// Add link params to array
Links.push(x + ";" + y + ";" + linkWidth + ";" + linkHeight + ";" + href);
}
// Link hover
function on_mousemove (ev) {
var x, y;
// Get the mouse position relative to the canvas element
if (ev.layerX || ev.layerX == 0) { // For Firefox
x = ev.layerX;
y = ev.layerY;
}
// Link hover
for (var i = Links.length - 1; i >= 0; i--) {
var params = new Array();
// Get link params back from array
params = Links[i].split(";");
var linkX = parseInt(params[0]),
linkY = parseInt(params[1]),
linkWidth = parseInt(params[2]),
linkHeight = parseInt(params[3]),
linkHref = params[4];
// Check if cursor is in the link area
if (x >= linkX && x <= (linkX + linkWidth) && y >= linkY && y <= (linkY + linkHeight)){
document.body.style.cursor = "pointer";
hoverLink = linkHref;
break;
}
else {
document.body.style.cursor = "";
hoverLink = "";
}
};
}
// Link click
function on_click(e) {
if (hoverLink){
window.open(hoverLink); // Use this to open in new tab
//window.location = hoverLink; // Use this to open in current window
}
}
// Ready for use ! You are welcome !
drawLink(95,93,"http://www.facebook.com/","Me at facebook");
drawLink(95,110,"http://plus.google.com/","Me at G+");
}
</script>
</head>
<body onload="OnLoad();">
<canvas id="myCanvas" width="450" height="250" style="border:1px solid #eee;">
Canvas is not supported in your browser ! :(
</canvas>
</body>
</html>
回答by Simon Sarris
There is nothing built into do it, but you can emulate the function of links if you wanted to. You can remember where the text is, color it differently, give it a different cursor when the user mouses-over that area, and redirect the user to another page when he or she clicks on it.
没有任何内置功能可以做到这一点，但是如果您愿意，您可以模拟链接的功能。您可以记住文本的位置、不同的颜色、在用户将鼠标悬停在该区域上时为其指定不同的光标，并在用户单击时将其重定向到另一个页面。
回答by Shamaila Tahir
I think another easy idea is to put a div at the position where you want the link to appear on the canvas and put your link at the div. All you will have to do is to position and style the div correctly.
我认为另一个简单的想法是在您希望链接出现在画布上的位置放置一个 div，并将您的链接放在 div 上。您所要做的就是正确定位和设置 div 的样式。
回答by John Hood
"I think another easy idea is to put a div at the position where you want the link to appear on the canvas and put your link at the div. All you will have to do is to position and style the div correctly." -Shamaila Tahir
“我认为另一个简单的想法是将 div 放在您希望链接出现在画布上的位置，并将您的链接放在 div 上。您所要做的就是正确定位 div 并为其设置样式。” -沙迈拉·塔希尔
I personally like the idea of using links on top of the canvas and here is a full page sized canvas example. You could use this example for many things, and not just the canvas, so why not get comfortable with it. `
我个人喜欢在画布顶部使用链接的想法，这里有一个整页大小的画布示例。您可以将此示例用于许多用途，而不仅仅是画布，那么为什么不适应它呢。`
<!DOCTYPE html>
<HEAD>
<style type="text/css">
html { height: 100%; width: 100%; overflow: hidden; }
body {
position: absolute;
height: 100%;
width: 100%;
overflow:hidden;
}
#contactBackground{
position: absolute;
height:100%;
width: 100%;
border: 2px solid green;
}
#contactBackground:hover{
border: 2px solid red;}
#contact{
position: absolute;
height:15%;
top: 52%;
left:70%;
width: 10%;
background-size:20%,20%;
}
#onOff{
position: absolute;
height:15%;
top: 52%;
left:20%;
width: 10%;
background-size:20%,20%;
}
#onOff:hover{border: 2px solid red;}
</style><TITLE>Kewl!! Buttons and Links with Canvas</TITLE></HEAD>
<script type="text/javascript">
window.addEventListener('load', canvas, false);
function canvas(){
var link="contact";
var canvas = document.getElementById("canvas");
var context = canvas.getContext('2d');
canvas.width = document.body.clientWidth;
canvas.height = document.body.clientHeight;
contact = document.getElementById("contact");
onOff = document.getElementById("onOff");
document.getElementById("onOff").style.visibility="visible";
switchLinks(link);
function switchLinks(isLink){
if(isLink!="contact"){
document.getElementById("contact").style.visibility="hidden";
}
if(isLink=="contact"){
document.getElementById("contact").style.visibility="visible";
}
}
onOff.addEventListener("mousedown",contactFunction, false);
function contactFunction(){
if(link=="contact"){link="";}else{link="contact";}
switchLinks(link);
}
}
</script><body>
<canvas id="canvas" width="0" height="0">Your browser does not support the HTML 5 Canvas.
</canvas>
<span id="contact" style="display:hidden">
<a href="mailto:Dude your Awesome!"><img id="contactBackground" src="https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQP5qi1TPhjAPOfbogNgppFdc4r1LoNmr5D1n-NBfr7ll3x9VlY9w" alt="Send a message" title="Email" /></a>
</span>
<img id="onOff" src="https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRXvh9Fej5ZhBQstjlSpQbRLx46h47KS2IO_WIfoyyrHk_essLU" style="display:hidden" />
</body></HTML>``
