If you want to draw pictures, make animations or even develop mini-games on web pages, you can use the
If you want to draw pictures, make animations or even develop mini-games on web pages, the HTML5 <canvas></canvas> tag is a very practical tool. It itself is just a blank canvas, and the real magic lies in using JavaScript to control how and what it draws.
Create Canvas elements
First, add a <canvas></canvas> tag to HTML:
<canvas id="myCanvas" width="500" height="300"></canvas>
This tag is transparent by default, has no content, and does not come with any drawing capabilities. You can define its dimensions by setting width and height properties. If not set, the default size (usually 300x150) is used.
Then get the element in JavaScript and get the drawing context:
const canvas = document.getElementById('myCanvas'); const ctx = canvas.getContext('2d');
ctx is the object you use to "draw", and almost all operations revolve around it.
Draw basic graphics
Once you have the context, you can start drawing things. For example, drawing a simple rectangle:
ctx.fillStyle = 'blue'; ctx.fillRect(50, 50, 100, 100);
This code sets the fill color to blue, and then starts from coordinates (50, 50), and draws a rectangle of 100 pixels in width and height.
You can also draw borders, circles, lines, etc. For example, draw a red circle:
ctx.beginPath(); ctx.arc(200, 150, 40, 0, Math.PI * 2); ctx.fillStyle = 'red'; ctx.fill(); ctx.closePath();
-
beginPath()means starting a new path; -
arc(x, y, radius, startAngle, endAngle)is the method of drawing circles; -
fill()fills the path; -
closePath()closes the path.
How to do animation and interaction?
Canvas can not only draw statically, but also create animation effects. A common practice is to constantly clear the canvas and repaint the contents of the painting. For example, do an animation of a small ball moving:
let x = 0;
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear canvas ctx.beginPath();
ctx.arc(x, 150, 20, 0, Math.PI * 2);
ctx.fillStyle = 'green';
ctx.fill();
x = 2;
if (x > canvas.width) x = 0; // loop requestAnimationFrame(draw); // continuously draw}
draw();This will enable the effect of a small ball moving back and forth on the screen. You can also interact with mouse events or touch events, such as clicking on the canvas to change the color, dragging animals, etc.
Notes and FAQs
- Resolution problem : If the image is blurred after the page is scaled, it may be because the CSS sets the canvas size but does not adjust it to the actual pixels. It is recommended to keep
canvas.widthandcanvas.heightmatching the display size. - Performance optimization : Try to update only the changing part when repainting frequently, not the entire canvas.
- Browser compatibility : Modern browsers basically support Canvas, but there may be problems on older versions of IE.
- Export picture : You can use
canvas.toDataURL()method to save the current picture as a picture.
Basically that's it. Canvas doesn't seem complicated, but there are many details, especially when it comes to animation, interaction or a lot of graphics processing, you need to practice more.
The above is the detailed content of How to use HTML5 canvas?. For more information, please follow other related articles on the PHP Chinese website!
Hot AI Tools
Undress AI Tool
Undress images for free
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
Audio and Video: HTML5 VS Youtube Embedding
Jun 19, 2025 am 12:51 AM
HTML5isbetterforcontrolandcustomization,whileYouTubeisbetterforeaseandperformance.1)HTML5allowsfortailoreduserexperiencesbutrequiresmanagingcodecsandcompatibility.2)YouTubeofferssimpleembeddingwithoptimizedperformancebutlimitscontroloverappearanceand
What is the purpose of the input type='range'?
Jun 23, 2025 am 12:17 AM
inputtype="range" is used to create a slider control, allowing the user to select a value from a predefined range. 1. It is mainly suitable for scenes where values ??need to be selected intuitively, such as adjusting volume, brightness or scoring systems; 2. The basic structure includes min, max and step attributes, which set the minimum value, maximum value and step size respectively; 3. This value can be obtained and used in real time through JavaScript to improve the interactive experience; 4. It is recommended to display the current value and pay attention to accessibility and browser compatibility issues when using it.
Adding drag and drop functionality using the HTML5 Drag and Drop API.
Jul 05, 2025 am 02:43 AM
The way to add drag and drop functionality to a web page is to use HTML5's DragandDrop API, which is natively supported without additional libraries. The specific steps are as follows: 1. Set the element draggable="true" to enable drag; 2. Listen to dragstart, dragover, drop and dragend events; 3. Set data in dragstart, block default behavior in dragover, and handle logic in drop. In addition, element movement can be achieved through appendChild and file upload can be achieved through e.dataTransfer.files. Note: preventDefault must be called
How can you animate an SVG with CSS?
Jun 30, 2025 am 02:06 AM
AnimatingSVGwithCSSispossibleusingkeyframesforbasicanimationsandtransitionsforinteractiveeffects.1.Use@keyframestodefineanimationstagesforpropertieslikescale,opacity,andcolor.2.ApplytheanimationtoSVGelementssuchas,,orviaCSSclasses.3.Forhoverorstate-b
HTML audio and video: Examples
Jun 19, 2025 am 12:54 AM
Audio and video elements in HTML can improve the dynamics and user experience of web pages. 1. Embed audio files using elements and realize automatic and loop playback of background music through autoplay and loop properties. 2. Use elements to embed video files, set width and height and controls properties, and provide multiple formats to ensure browser compatibility.
What is WebRTC and what are its main use cases?
Jun 24, 2025 am 12:47 AM
WebRTC is a free, open source technology that supports real-time communication between browsers and devices. It realizes audio and video capture, encoding and point-to-point transmission through built-in API, without plug-ins. Its working principle includes: 1. The browser captures audio and video input; 2. The data is encoded and transmitted directly to another browser through a security protocol; 3. The signaling server assists in the initial connection but does not participate in media transmission; 4. The connection is established to achieve low-latency direct communication. The main application scenarios are: 1. Video conferencing (such as GoogleMeet, Jitsi); 2. Customer service voice/video chat; 3. Online games and collaborative applications; 4. IoT and real-time monitoring. Its advantages are cross-platform compatibility, no download required, default encryption and low latency, suitable for point-to-point communication
How to create animations on a canvas using requestAnimationFrame()?
Jun 22, 2025 am 12:52 AM
The key to using requestAnimationFrame() to achieve smooth animation on HTMLCanvas is to understand its operating mechanism and cooperate with Canvas' drawing process. 1. requestAnimationFrame() is an API designed for animation by the browser. It can be synchronized with the screen refresh rate, avoid lag or tear, and is more efficient than setTimeout or setInterval; 2. The animation infrastructure includes preparing canvas elements, obtaining context, and defining the main loop function animate(), where the canvas is cleared and the next frame is requested for continuous redrawing; 3. To achieve dynamic effects, state variables, such as the coordinates of small balls, are updated in each frame, thereby forming
How to check if a browser can play a specific video format?
Jun 28, 2025 am 02:06 AM
To confirm whether the browser can play a specific video format, you can follow the following steps: 1. Check the browser's official documents or CanIuse website to understand the supported formats, such as Chrome supports MP4, WebM, etc., Safari mainly supports MP4; 2. Use HTML5 tag local test to load the video file to see if it can play normally; 3. Upload files with online tools such as VideoJSTechInsights or BrowserStackLive for cross-platform detection. When testing, you need to pay attention to the impact of the encoded version, and you cannot rely solely on the file suffix name to judge compatibility.
