


html5 Canvas drawing tutorial (5)—arc method of drawing curves in canvas_html5 tutorial skills
In this article Drawing Lines on Canvas, I talked about how to draw straight lines. Logically, this article on drawing curves should have been published long ago, but since drawing curves on canvas is quite special, I haven’t figured it out yet, so Try it step by step.
One of the difficulties in drawing curves in canvas is that there are only 4 functions for curves! They are arc, arcTo, quadraticCurveTo, and bezierCurveTo. Let me start with the simplest arc method.
The function of arc is to draw a regular arc, which can be a complete circle or a certain arc of a circle. The syntax for arc is as follows: 🎜>
context.arc(x, y, radius, startAngle, endAngle, anticlockwise)
I will explain its parameters, that is,
arc(center of circle x, center of circle y, radius, starting angle, ending angle, counterclockwise or not)
The code is as follows:
ctx.arc(400,400,20,0,Math.PI*2); ctx.fill(); ctx.stroke();
Copy code
The code is as follows:
ctx.arc(400,400,20,0 ,Math.PI*2/4);

ctx.arc(400,400,20,0 ,Math.PI*2/4,true);

The code is as follows:
ctx.arc(400,400,20,Math .PI*2/4,Math.PI*2 Math.PI);
If our starting point is 90 degrees and the end point is also 90 degrees, the result is that nothing can be drawn, so I put the end point The angle was changed to 180 degrees, and finally the graph below was obtained.
Copy code
Code As follows:
However, this approach is just looking for trouble, and normal people would not use it.
Summary: The arc method of Canvas is a way to draw a positive arc. It can only draw positive arcs and cannot draw other strange arcs, such as S-shape - although I like it best S-shaped.

H5 improves web user experience with multimedia support, offline storage and performance optimization. 1) Multimedia support: H5 and elements simplify development and improve user experience. 2) Offline storage: WebStorage and IndexedDB allow offline use to improve the experience. 3) Performance optimization: WebWorkers and elements optimize performance to reduce bandwidth consumption.

HTML5 code consists of tags, elements and attributes: 1. The tag defines the content type and is surrounded by angle brackets, such as. 2. Elements are composed of start tags, contents and end tags, such as contents. 3. Attributes define key-value pairs in the start tag, enhance functions, such as. These are the basic units for building web structure.

HTML5 is a key technology for building modern web pages, providing many new elements and features. 1. HTML5 introduces semantic elements such as, , etc., which enhances web page structure and SEO. 2. Support multimedia elements and embed media without plug-ins. 3. Forms enhance new input types and verification properties, simplifying the verification process. 4. Offer offline and local storage functions to improve web page performance and user experience.

Best practices for H5 code include: 1. Use correct DOCTYPE declarations and character encoding; 2. Use semantic tags; 3. Reduce HTTP requests; 4. Use asynchronous loading; 5. Optimize images. These practices can improve the efficiency, maintainability and user experience of web pages.

Web standards and technologies have evolved from HTML4, CSS2 and simple JavaScript to date and have undergone significant developments. 1) HTML5 introduces APIs such as Canvas and WebStorage, which enhances the complexity and interactivity of web applications. 2) CSS3 adds animation and transition functions to make the page more effective. 3) JavaScript improves development efficiency and code readability through modern syntax of Node.js and ES6, such as arrow functions and classes. These changes have promoted the development of performance optimization and best practices of web applications.

H5 is not just the abbreviation of HTML5, it represents a wider modern web development technology ecosystem: 1. H5 includes HTML5, CSS3, JavaScript and related APIs and technologies; 2. It provides a richer, interactive and smooth user experience, and can run seamlessly on multiple devices; 3. Using the H5 technology stack, you can create responsive web pages and complex interactive functions.

H5 and HTML5 refer to the same thing, namely HTML5. HTML5 is the fifth version of HTML, bringing new features such as semantic tags, multimedia support, canvas and graphics, offline storage and local storage, improving the expressiveness and interactivity of web pages.

H5referstoHTML5,apivotaltechnologyinwebdevelopment.1)HTML5introducesnewelementsandAPIsforrich,dynamicwebapplications.2)Itsupportsmultimediawithoutplugins,enhancinguserexperienceacrossdevices.3)SemanticelementsimprovecontentstructureandSEO.4)H5'srespo


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