Creating an HTML 5 canvas painting application - Opera Developer. By Mihai Sucan Table of contents Introduction My previous HTML5 canvas tutorial provided you with insight into the numerous use cases for canvas in web applications. In this article we will explore how you can write your own canvas-based painting application. Making a web application that allows users to draw on a canvas requires several important steps: setting up your HTML document with a canvas context (a canvas element with an id), setting up your script to target that canvas context and draw inside it and adding the required mouse event handlers for user interaction and associated logic. The final painting application example looks like this: To make it easier to follow along with the code walkthrough presented below, you can download the full code example and follow along with it as you read the article.
Getting started with the HTML We shall begin with a minimal HTML document: As you can see, we only have the bare bones of an HTML document here, with a canvas element contained inside. SVG vs. Canvas on Trivial Drawing Application. Recent popularity on Canvas development and support has made the need for SVG somewhat vague. As SVG is still not widely adopted and Canvas has recently acquired lot of support from developers and browsers, some might question the role of SVG in future web. However, this is not the case and there is a strong need for SVG. To illustrate this, we will create a small a) vector drawing application with SVG and b) pixel drawing application with Canvas.
Both are easy and straightforward to develop. The assumption is, that these are the typical applications for both techniques. What will be interesting, though, is when we swap the standard and the target application. This experiment gives insight on the limits of each standard. SVG's native "file format" is naturally SVG (XML), while Canvas' is bitmap, such as PNG. We'll then attempt to layer and combine the SVG vector drawing application with the Canvas pixel drawing application. Canvas dans <html5> par l'exemple - Démonstrations live. Zwibbler: A simple drawing program using Javascript and Canvas -
Tested under Firefox 3.5.6 and Google Chrome 3.0.195.38 This project extends the technique I created for imprecise line-drawing to create an entire vector graphics application, similar to Inkscape. It is written almost entirely in Javascript, except for a server-side program that renders text. See below if you are interested in the implementation and coding parts. Features Download and share your drawings in PNG, PDF, or SVG formats. Box, circle, lines, and curve primitive shapes Shadows when supported by browser Text in several hand-drawn fonts rendered on the server Rotate & scale shapes individually or in groups Select colours using an HSV colour wheel. List of keyboard shortcuts The keyboard is the only way to do some things. Saving and loading Drawings can be stored on the website by clicking on "Save". If you don't want to create an account, the "Save" option will also allow you to download your drawing as an image.
Drawing simple shapes No two shapes are alike. Drawing lines and curves. Let’s Call It a Draw(ing Surface) - Dive Into HTML 5. You are here: Home Dive Into HTML5 Diving In HTML 5 defines the <canvas> element as “a resolution-dependent bitmap canvas which can be used for rendering graphs, game graphics, or other visual images on the fly.” A canvas is a rectangle in your page where you can use JavaScript to draw anything you want. So what does a canvas look like? Invisible canvas The markup looks like this: Let’s add a dotted border so we can see what we’re dealing with. Canvas with border You can have more than one <canvas> element on the same page. Let’s expand that markup to include an id attribute: Now you can easily find that <canvas> element in the DOM. var a_canvas = document.getElementById("a"); Simple Shapes Every canvas starts out blank.
Click to draw on this canvas The onclick handler called this function: function draw_b() { var b_canvas = document.getElementById("b"); var b_context = b_canvas.getContext("2d"); b_context.fillRect(50, 25, 150, 100); } And then there’s this Every canvas has a drawing context Paths path . Dynamic Content Injection with HTML5 Canvas and Video. HTML 5 Canvas Example { William Malone } By William Malone With HTML5 support emerging, I have decided to investigate the drawing capabilities. In the tutorial I will focus on drawing on the new element called a "canvas". I created an example icon in Photoshop and will reproduce it by drawing on a canvas with JavaScript. Browser Capability At the time of this article HTML5 is not yet standard and not fully supported by the major browsers.
Despite my attempts to keep my example consistent between browsers, there were some aspects I was unable to overcome. Let's take a look: Browser consistency added a lot of extra complexity and code. Simple Example Implementation We shrug off the browser capability issues for now (hopefully the future will bring full support in all browsers) so we can take a much simpler look at how this example was created. Markup First let's take a look at the markup: Now we have a blank canvas. Script The canvas element will provide an area on which we will use JavaScript to place our drawing. There you have it! <! Tutoriel canvas - MDC.