[英]DrawImage on Canvas HTML5 Error
因此,当我尝试像这样在画布上绘制图像时(工作正常):
<html>
<head>
<title>HTML5 canvas</title>
<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
<script>
$(document).ready(start);
var image1;
function start() {
var ctx = $('#canvas').get(0).getContext('2d');
image1 = new Image;
image1.src = "/arenag/arenagimg/BeastBear.jpg";
image1.onload = function () {
ctx.drawImage(image1.src,200, 200, 100, 100);
};
}
</script>
<style type="text/css">
#framework {
border: 2px solid #000;
width: 100%;
text-align: center;
}
#canvas {
background-color: #00FFE2;
margin-right: auto;
margin-left: auto;
}
</style>
</head>
<body>
<div id="framework">
<canvas id="canvas" width="1024" height="768"></canvas>
</div>
</body>
</html>
然后我添加一个名为imagefactory.js的文件夹并创建一个ImageFactory类,并在该类中创建一个名为drawImage的函数:
var ImageFactory = function (ctx) {
this.ctx = ctx;
this.drawImage = function (image_arg, image_x, image_y, image_w, image_h) {
var _this = this;
var image = new Image;
image.src = image_arg;
image.onload = function () {
_this.ctx.drawImage(image.src, image_x, image_y, image_w, image_h);
};
};
};
然后,我只是尝试在主文件中调用该函数:
<html>
<head>
<title>HTML5 canvas</title>
<script src="//code.jquery.com/jquery-1.11.0.min.js"></script>
<script>
$(document).ready(start);
var image;
function start() {
image = '/arenag/arenagimg/BeastBear.jpg';
var ctx = $('#canvas').get(0).getContext('2d');
var imageFactory=new ImageFactory(ctx);
imageFactory.drawImage(image,200, 200, 100, 100);
}
</script>
<style type="text/css">
#framework {
border: 2px solid #000;
width: 100%;
text-align: center;
}
#canvas {
background-color: #00FFE2;
margin-right: auto;
margin-left: auto;
}
</style>
</head>
<body>
<div id="framework">
<canvas id="canvas" width="1024" height="768"></canvas>
</div>
</body>
</html>
我收到此错误(在画布所在的主(HTML)文件的36行中):
Uncaught TypeError: Failed to execute 'drawImage' on 'CanvasRenderingContext2D': The provided value is not of type '(HTMLImageElement or HTMLVideoElement or HTMLCanvasElement or ImageBitmap)'
还有与另一个错误相关的错误(我的意思是,如果没有此错误,那么也就没有第一个错误):
[object%20HTMLImageElement]:1 GET http://phpcasovi.dev/arenag/klase/[object%20HTMLImageElement] 404 (Not Found)
我想为您提供解决的方法:当我更改var image = new Image;
改为var image = {};
然后没有错误,但是因为var image
不等于new Image
那么就根本没有图像。所以我认为bug就是我说var image = new Image;
那一行var image = new Image;
但我不知道为什么会有错误(为什么要这样)?
context.drawImage
第一个参数应该是Image-Object
而不是image.src
从docs ,
ctx.drawImage(image, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight);
,image
, 绘制context
的元素。 该规范允许使用任何canvas image source
(CanvasImageSource
),例如HTMLImageElement
,HTMLVideoElement
,HTMLCanvasElement
或ImageBitmap
。
var ImageFactory = function(ctx) { this.ctx = ctx; this.drawImage = function(image_arg, image_x, image_y, image_w, image_h) { var _this = this; var image = new Image(); image.src = image_arg; image.onload = function() { _this.ctx.drawImage(image, image_x, image_y, image_w, image_h); }; }; }; $(document).ready(start); function start() { var image = 'https://www.google.com/images/branding/googlelogo/1x/googlelogo_white_background_color_272x92dp.png'; var ctx = $('#canvas').get(0).getContext('2d'); var imageFactory = new ImageFactory(ctx); imageFactory.drawImage(image, 200, 200, 100, 100); }
#framework { border: 2px solid #000; width: 100%; text-align: center; } #canvas { background-color: #00FFE2; margin-right: auto; margin-left: auto; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script> <div id="framework"> <canvas id="canvas" width="1024" height="768"></canvas> </div>
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