将图像绘制到html5画布

我想绘制一个图像到html5画布，但不能完全记住它是如何完成的。将图像绘制到html5画布

我有以下的html文件：

<html> 
<head> 
<title>Understanding Business</title> 

<section hidden> 
<img id = "startButton" src = "startButton.png" alt = "Start Button" height = "40" width = "50" href = "javascript:drawFirstGameElements();"> 
</section> 
</head> 

<body onLoad = "drawStartButton()"> 
<h1>Understanding Business</h1> 
<canvas id ="gameCanvas" width = "1000" height= "500" style = "border:1px solid #000000;">Your browser does not support the HTML5 canvas.</canvas> 

<script type = "text/javascript"> 
window.onload = function(){ 
var gameCanvas = document.getElementById("gameCanvas"); 
var context = gameCanvas.getContext("2d"); 
//gameCanvas.addEventListener('onclick', clickReporter, false); 
gameCanvas.addEventListener('mouseMove', function(event){ 
    var mousePosition = getMouseCoords(gameCanvas, event); 

}); 
/* Add some global variables */ 
var image = new Image(); 
var imageSource; 
var imageX; 
var imageY; 


function drawStartButton(){ 
/*image.onload = function(){ 
    context.drawImage(image, 500, 250); 
}; 
image.src = "startButton.png"; */ 
var startButtonImg = document.getElementById("startButton"); 
context.drawImage(startButtonImg, 500, 250); 
} 

function drawFirstGameElements(){ 
drawDescriptionBox1; 
} 
function drawDescriptionBox1(){ 
context.moveTo(100, 400); 
context.lineTo(150, 400); 
context.lineTo(150, 450); 
context.lineTo(100, 450); 
context.lineTo(100, 400); 
context.moveTo(110, 425); 
context.strokeText("Asset"); 
} 

//Function to get mouse coordinates on canvas 
function getMouseCoords(gameCanvas, event){ 
var rect = gameCanvas.getBoundingClientRect(), root = document.documentElement; 

//return mouse position 
var mouseX = event.clientX - rect.top - root.scrollTop; 
var mouseY = event.clientY - rect.left - root.scrollLeft; 
return{ 
    x: mouseX, 
    y: mouseY 
}; 
} 
}

出于某种原因，当我查看该页面在浏览器中，虽然显示在画布上，“开始按钮图像“不显示在画布上。自从我上次使用HTML5画布以来，已经有一段时间了，我无法弄清楚自己做错了什么......有人能指出我的方向吗？

干杯，

编辑

代码更新建议，以反映变化，但我仍然有同样的问题。还有其他建议吗？

来源

2012-11-12 someone2088

建议密切的“太本地化”，因为错误是一个单纯的错字和无关的问题的内容。 – Alnitak

错字在你的代码：

var gameCanvas = document.getElementById("gameCanvas"); 
var context = gameCanvas.getContext("2d"); 
//gameCanvas.addEventListener('onclick', clickReporter, false); 
gameCanvas.addEventListener('mouseMove', function(event){ 
    var mousePosition = getMouseCoords(gameCanvas, event); 

}); // HERE ADD); 

/* Add some global variables */ 
var image = new Image(); 
var imageSource; 
var imageX; 
var imageY; 
//HERE DELETE THE }

的jsfiddle：http://jsfiddle.net/RqbPn/

来源

2012-11-12 13:06:13 jazzytomato

感谢您的回复。我做了建议的更改并保存了该文件，但是当我在浏览器中重新加载页面时，我仍然只是看到空白画布... – someone2088

其他建议？ – someone2088

删除和drawStartButton函数也是如我在小提琴中所做的那样。它可能会在window.onload函数之前调用，所以当您尝试绘制它时画布不存在 – jazzytomato

将图像绘制到html5画布

回答

相关问题