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What does the Canvas tag mean?

云罗郡主
云罗郡主Original
2019-01-26 10:55:299052browse

Canvas is an HTML element into which images can be drawn using scripts (usually JavaScript). It can be used to create photo albums or create simple (and not so simple) animations, or even for real-time video processing and rendering.

What does the Canvas tag mean?

In HTML, the canvas tag is used to define graphics, such as charts and other images. Scripts must be used to draw graphics, such as drawing a red rectangle, gradient rectangle on the canvas. , a colored rectangle, and some colored text.

1. What is canvas?

The HTML5 canvas element is used for drawing graphics, which is done through scripts (usually JavaScript).

The canvas tag is just a graphics container, you must Use scripts to draw graphics.

You can use canvas to draw paths, boxes, circles, characters and add images in a variety of ways.

2.Basic use of Canvas

style="border:1px solid #000000 ;">

2.1 The element

looks the same as the What does the Canvas tag mean? tag, except has only two optional attributes, width and height, but no src and alt attributes.

If the widht and height attributes are not set for , the default width is 300, height is 150, and the units are px. You can also use css attributes to set the width and height, but if the width and height attributes are inconsistent with the initial ratio, it will be distorted. Therefore, it is recommended that you never use css properties to set the width and height of .

2.2 Case

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
<style type="text/css">
canvas {
    border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="tutorial" width="300" height="300"></canvas>
<script type="text/javascript">
function draw(){
    var canvas = document.getElementById(&#39;tutorial&#39;);
    if(!canvas.getContext) return;
    var ctx = canvas.getContext("2d");
    ctx.fillStyle = "rgb(200,0,0)";
      //绘制矩形
    ctx.fillRect (10, 10, 55, 50);
 
    ctx.fillStyle = "rgba(0, 0, 200, 0.5)";
    ctx.fillRect (30, 30, 55, 50);
}
draw();
</script>
</body>
</html>

The effect is as follows:

What does the Canvas tag mean?


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