Javascript 在画布上随机显示图像
我需要帮助来使用Javascript和HTML5编写代码。请告知Javascript 在画布上随机显示图像,javascript,image,canvas,Javascript,Image,Canvas,我需要帮助来使用Javascript和HTML5编写代码。请告知 <HTML> <HEAD> <SCRIPT language="javascript"> function Add() { if (document.getElementById('amount').value < 100){ document.getElementById('amount').value++; new
<HTML>
<HEAD>
<SCRIPT language="javascript">
function Add() {
if (document.getElementById('amount').value < 100){
document.getElementById('amount').value++;
newIMG = document.createElement("IMG");
newIMG.src = 'jef-frog.gif';
newIMG.width = 50;
newIMG.height = 50;
document.getElementById("imagedest").appendChild(newIMG);
}
}
function Remove() {
if(document.getElementById('amount').value > 0)
document.getElementById('amount').value--;
imagedest.removeChild(imagedest.lastChild);
}
function numeralsOnly(evt) {
evt = (evt) ? evt : event;
var charCode = (evt.charCode) ? evt.charCode : ((evt.keyCode) ? evt.keyCode :
((evt.which) ? evt.which : 0));
if (charCode > 31 && (charCode < 48 || charCode > 57)) {
return false;
}
return true;
}
</SCRIPT>
</HEAD>
<BODY>
<H2>TESTING</H2>
PREY
<BR/>
<img src="jef-frog.gif" alt="frogsonice.com" width="100" height="100"/>
<BR/>
<FORM>
<INPUT type="button" value="+" onClick="Add()">
<input type="text" id="amount" value=0 maxlength="3" size="1" onkeypress="return numeralsOnly(event)">
<INPUT type="button" value="-" onClick="Remove()">
<div id='imagedest'>
</div>
</FORM>
</BODY>
</HTML>
函数Add(){
if(document.getElementById('amount')。值<100){
document.getElementById('amount')。value++;
newIMG=document.createElement(“IMG”);
newIMG.src='jef frog.gif';
newIMG.width=50;
新高度=50;
document.getElementById(“imagedest”).appendChild(newIMG);
}
}
函数删除(){
if(document.getElementById('amount')。值>0)
document.getElementById('amount')。值--;
imagedest.removeChild(imagedest.lastChild);
}
数字功能(evt){
evt=(evt)?evt:事件;
var charCode=(evt.charCode)?evt.charCode:((evt.keyCode)?evt.keyCode:
((evt.which)?evt.which:0));
如果(字符码>31&(字符码<48 | |字符码>57)){
返回false;
}
返回true;
}
测试
猎物
我已经测试了代码,它将显示在
标记中,但我想让它显示在上面创建的画布中。我不知道如何在画布上捕捉这个东西。有人能帮忙吗?您需要使用画布api在上面绘制一些东西
- 获取画布(var canvas=document.getElementById(“画布”);)
- 获取2D上下文(var ctx=canvas.getContext(“2D”);)
- 绘制图像()
<html>
<head>
<script type="application/javascript">
function draw() {
var canvas = document.getElementById("canvas");
if (canvas.getContext) {
var ctx = canvas.getContext("2d");
ctx.fillStyle = "rgb(200,0,0)";
ctx.fillRect (10, 10, 55, 50);
ctx.fillStyle = "rgba(0, 0, 200, 0.5)";
ctx.fillRect (30, 30, 55, 50);
}
}
</script>
</head>
<body onload="draw();">
<canvas id="canvas" width="150" height="150"></canvas>
</body>
</html>
函数draw(){
var canvas=document.getElementById(“canvas”);
if(canvas.getContext){
var ctx=canvas.getContext(“2d”);
ctx.fillStyle=“rgb(200,0,0)”;
ctx.fillRect(10,10,55,50);
ctx.fillStyle=“rgba(0,02000,0.5)”;
ctx.fillRect(30,30,55,50);
}
}
'code'函数Remove(){if(document.getElementById('amount').value>0)document.getElementById('amount').value--;imagedest.removeChild(imagedest.lastChild);c5_context.drawImage(bgima,destX,destY,600300)//c5_context.drawImage(frog,x,y,58100)。value--}函数数值(evt){evt=(evt)evt:event;var charCode=(evt.charCode)?evt.charCode:((evt.keyCode)?evt.keyCode:((evt.which)?evt.which:0));if(charCode>31&(charCode<48 | | charCode>57)){return false;}return true;}'code'我想,我不明白你的问题:-(