What are the common Canvas drawing techniques?

What are the common methods for canvas painting, specific code examples are required

In front-end development, we often use canvas for drawing operations. Canvas is a drawing API provided in HTML5, through which we can draw 2D graphics, perform image processing, create animations, etc. on web pages.

Let’s introduce some commonly used canvas painting methods and provide corresponding code examples.

1. Create canvas element:
   In the HTML file, use the <canvas></canvas> tag to create the canvas element and specify its width and height.

   <canvas id="myCanvas" width="300" height="150"></canvas>

2. Get the drawing context:
   Through JavaScript code, we can get the drawing context of the canvas. The drawing context is an object used for drawing operations, and it provides a wealth of methods and properties.

   var canvas = document.getElementById("myCanvas");
   var ctx = canvas.getContext("2d");

3. Draw a rectangle:
   Use the fillRect() method to draw a filled rectangle.

   ctx.fillStyle = "red"; // 设置填充颜色
   ctx.fillRect(10, 10, 100, 50); // 绘制矩形，参数分别为起始点的x、y坐标，矩形的宽度和高度

4. Draw text:
   Use the fillText() method to draw text on the canvas.

   ctx.font = "30px Arial"; // 设置字体样式
   ctx.fillStyle = "blue"; // 设置填充颜色
   ctx.fillText("Hello World", 50, 50); // 绘制文本，参数分别为文本内容，起始点的x、y坐标

5. Drawing paths:
   Use paths to create complex graphics, such as straight lines, curves, arcs, etc. The core methods are beginPath() (open a new path), moveTo() (move the drawing position to the specified point), lineTo() (draw a straight line) , arc() (draw arc), etc.

   ctx.beginPath();
   ctx.moveTo(50, 50);
   ctx.lineTo(100, 100);
   ctx.lineTo(150, 50);
   ctx.closePath(); // 闭合路径
   ctx.strokeStyle = "green"; // 设置描边颜色
   ctx.stroke(); // 绘制描边

6. Draw a picture:
   Use the drawImage() method to draw a picture on the canvas.

   var img = new Image();
   img.src = "image.jpg";
   img.onload = function() {
     ctx.drawImage(img, 10, 10); // 绘制图片，参数分别为图片对象、起始点的x、y坐标
   }

7. Clear the drawing area:
   Use the clearRect() method to clear the specified area on the canvas.

   ctx.clearRect(0, 0, canvas.width, canvas.height); // 参数分别为起始点的x、y坐标，清除区域的宽度和高度

These are some common methods in canvas painting, through which we can achieve various desired painting effects. Of course, this is just a simple code example, and more drawing combinations and drawing logic may be needed in actual applications. I hope this article can help more people understand how to use canvas and add a reference for front-end development.

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