Javascript drawing

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Computer programming. Intro to programming. Animation basics. Interactive programs. Becoming a community coder. Bonus: Resizing with variables. Logic and if Statements. Debugging programs. Writing clean code. Object-Oriented Design.

Becoming a better programmer. Learn how to use the JavaScript language and the ProcessingJS library to create fun drawings and animations.

javascript drawing

If you're new here, watch our intro video and get a brief tour of our programming course. Then get coding! What is Programming? Learning programming on Khan Academy. Drawing basics. Making drawings with code. Quick tip: number scrubbing. Challenge: Simple snowman. Drawing more shapes with code.Images can be displayed inside a canvas, where they can be integrated with the vector-drawing techniques of the canvas API. You can also select a portion of an image to display and apply the various transformations to your image to create interesting compositions and animations.

An alternate approach is to create an Image object in JavaScript and apply the src attribute to connect that image to a specific image file. For examples of both techniques, consider the following HTML code:. The easiest way to access an image is to use ordinary HTML to embed the image in the main page.

How to Draw Shapes on JavaScript’s Canvas for HTML5 and CSS3 Programming

Use the ordinary document. The drawImage function takes five parameters. The first is the name of an image object It must be the name of a JavaScript image object, not just the filename of an image. The next two parameters are the X and Y values of the top-left corner of the image, and the last two parameters are the size of the image width and height.

Use the new Image constructor to build a new image. If you create a JavaScript image, you must specify the src attribute to indicate the file associated with the image. It might take some time for the image to load. The image object has an onload property that accepts a callback function. Use this technique to wait until your drawing finishes. This program focuses in on the center of the goofy face:. Use the same drawImage command, but this time use a version with nine parameters:.

Image name: The first parameter is the name of the image not the filename, but the name of the JavaScript Image object.

javascript drawing

Top left corner of source: The first job is to choose the part of the original picture that will be displayed.

The next two parameters indicate the top left corner of a selection on the original picture. You might use an image editor like Gimp or IrfanView to determine the selection position and size.

Height and width of source: The next two parameters indicate the height and width of the source selection. Size of destination: The last two parameters describe the size of the destination image on the canvas.Now that we have set up our canvas environmentwe can get into the details of how to draw on the canvas. By the end of this article, you will have learned how to draw rectangles, triangles, lines, arcs and curves, providing familiarity with some of the basic shapes.

Working with paths is essential when drawing objects onto the canvas and we will see how that can be done. Before we can start drawing, we need to talk about the canvas grid or coordinate space. Our HTML skeleton from the previous page had a canvas element pixels wide and pixels high.

To the right, you see this canvas with the default grid overlayed. Normally 1 unit in the grid corresponds to 1 pixel on the canvas. The origin of this grid is positioned in the top left corner at coordinate 0,0. All elements are placed relative to this origin.

So the position of the top left corner of the blue square becomes x pixels from the left and y pixels from the top, at coordinate x,y. Later in this tutorial we'll see how we can translate the origin to a different position, rotate the grid and even scale it, but for now we'll stick to the default.

All other shapes must be created by combining one or more paths. Luckily, we have an assortment of path drawing functions which make it possible to compose very complex shapes. Each of these three functions takes the same parameters. Below is the draw function from the previous page, but now it is making use of these three functions.

The fillRect function draws a large black square pixels on each side. The clearRect function then erases a 60x60 pixel square from the center, and then strokeRect is called to create a rectangular outline 50x50 pixels within the cleared square. In upcoming pages we'll see two alternative methods for clearRectand we'll also see how to change the color and stroke style of the rendered shapes.

javascript drawing

Unlike the path functions we'll see in the next section, all three rectangle functions draw immediately to the canvas. Now let's look at paths. A path is a list of points, connected by segments of lines that can be of different shapes, curved or not, of different width and of different color. A path, or even a subpath, can be closed. The first step to create a path is to call the beginPath.

Internally, paths are stored as a list of sub-paths lines, arcs, etc which together form a shape. Every time this method is called, the list is reset and we can start drawing new shapes.

The second step is calling the methods that actually specify the paths to be drawn. We'll see these shortly. The third, and an optional step, is to call closePath. This method tries to close the shape by drawing a straight line from the current point to the start.

If the shape has already been closed or there's only one point in the list, this function does nothing. One very useful function, which doesn't actually draw anything but becomes part of the path list described above, is the moveTo function. You can probably best think of this as lifting a pen or pencil from one spot on a piece of paper and placing it on the next. When the canvas is initialized or beginPath is called, you typically will want to use the moveTo function to place the starting point somewhere else.

We could also use moveTo to draw unconnected paths. Take a look at the smiley face below. To try this for yourself, you can use the code snippet below.This article provides an introduction to canvas, and further resources to allow you to learn more. As we talked about in our HTML Multimedia and embedding module, the Web was originally just text, which was very boring, so images were introduced — first via the element embeds an image into the document. This however was still not enough.

While you could use CSS and JavaScript to animate and otherwise manipulate SVG vector images — as they are represented by markup — there was still no way to do the same for bitmap images, and the tools available were rather limited. As you'll see below, canvas provides many useful tools for creating 2D animations, games, data visualizations, and other types of app, especially when combined with some of the other APIs the web platform provides.

1.3: Basics of drawing - kdi.tauliasexstorey.pw Tutorial

The below example shows a simple 2D canvas-based bouncing balls animation that we originally met in our Introducing JavaScript objects module:. Around —, Mozilla started work on an experimental 3D canvas implementation.

How to Draw Shapes on JavaScript’s Canvas for HTML5 and CSS3 Programming

This became WebGLwhich gained traction among browser vendors, and was standardized around — WebGL allows you to create real 3D graphics inside your web browser; the below example shows a simple rotating WebGL cube:. This article will focus mainly on 2D canvas, as raw WebGL code is very complex. This element is used to define the area on the page into which the image will be drawn.

This is as simple as including the element on the page:. Inside the canvas tags, you can put some fallback content, which is shown if the user's browser doesn't support canvas.

Of course, the above message is really unhelpful! In a real example you'd want to relate the fallback content to the canvas content. For example, if you were rendering a constantly updating graph of stock prices, the fallback content could be a static image of the latest stock graph, with alt text saying what the prices are in text. Canvases with no explicit width and height default to pixels wide by pixels high.

Now add the following lines of JavaScript inside the element is used to embed or reference executable code; this is typically used to embed or refer to JavaScript code. Here we have stored a reference to the canvas in the canvas constant. In the second line we set both a new constant width and the canvas' width property equal to Window.

In the third line we set both a new constant height and the canvas' height property equal to Window. So now we have a canvas that fills the entire width and height of the browser window! You'll also see that we are chaining assignments together with multiple equals signs — this is allowed in JavaScript, and it is a good technique if you want to make multiple variables all equal to the same value. To get rid of the scrollbars, we need to remove the margin and also set overflow to hidden. Add the following into the element contains machine-readable information metadata about the document, like its title, scripts, and style sheets.

We need to do one final thing before we can consider our canvas template finished. To draw onto the canvas we need to get a special reference to the drawing area called a context. So that's it — our canvas is now primed and ready for drawing on! The ctx variable now contains a CanvasRenderingContext2D object, and all drawing operations on the canvas will involve manipulating this object. Let's do one last thing before we move on.

We'll color the canvas background black to give you a first taste of the canvas API.Have fun! Instead of working with pixels, you work with objects. Source Demo. HTML itself is not able to describe lines. Therefore, there is no built-in feature in the above-mentioned browsers for drawing lines. By implementing the Bresenham algorithm with JavaScript while applying some tricks, we will be able to draw lines in a good manner in respect to the browser runtime and memory footprints.

Using Canviz has advantages for your web application over generating and sending bitmapped images and image maps to the browser as the server only needs to have Graphviz generate xdot text; this is faster than generating bitmapped images.

Flotr enables you to draw appealing graphs in most modern browsers with an easy to learn syntax. It comes with great features like legend support, negative value support, mouse tracking, selection support, zoom support, event hooks, CSS styling support and much more.

This means every graphical object you create is also a DOM object, so you can attach JavaScript event handlers or modify them later. PlotKit is fully documented and there is a quick tutorial to get you started.

PlotKit is a complete rewrite of CanvasGraph. It is better structured and supported. The motivation for this work is to allow simple graph plotting in JavaScript without resorting to anything but your web browser. With jsDraw2D, you can draw advance drawings like cubic Bezier curve, general Bezier curve. The general Bezier curve can be of any degrees including linear, quadratic and cubic, open curve passing through given points and closed curve passing through given points. The library is cross-browser and fast.

However, due to the limitations of HTML, drawing on your web pages using JavaScript is slower compared to drawing in stand-alone applications.

Create drawings and diagrams with the free JavaScript library. The User interface allows interactive drawing by using your standard browser. No additional software and no third party plug ins.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information.

From there, you can add all kinds of other features like giving the user the ability to choose a line thickness, color, brush strokes, and even layers.

This should direct you on the right direction. I've added the below code to a jsfiddle. Let me know if you have trouble implementing this. It uses processing. A super short version, herewithout position:absolute in vanilla JavaScript. The main idea is to move the canvas' context to the right coordinates and draw a line. Learn more. Asked 10 years, 1 month ago.

Active 3 months ago. Viewed k times. Please help me how can I do? Please give some source code. Thank you. Han 5 5 silver badges 18 18 bronze badges. MartinJoo MartinJoo 2, 7 7 gold badges 26 26 silver badges 36 36 bronze badges. See also: How do I hand draw on canvas? Active Oldest Votes. Here is a working sample. Why do you do switch?

Drawing graphics

I'm trying to use this code, but have issues with the drawing being off vertically when I'm not scrolled all the way down on the page.

What should I change in this code? I know its a bit late, but I've tried this in Safari for the iPad and it does not work. Any fix for this?You can render anything you want in your browser with JavaScript. Most of these tools use JavaScript to render graphical shapes and interact with them.

But what if you want to create your own kind of diagrams or build your own editor? We split the set of JavaScript drawing libraries into two main categories: 1 — libraries with explicit support for software models e. JavaScripts libraries with predefined flowcharts or UML shapes and 2 — libraries with core support for drawing graphs and that could then be adapted to cover graphical modeling languages.

JointJS can be used to create either static diagrams or fully interactive diagramming tools and application builders. It has also a commercial version Rappid, see below. Rappid is the commercial extension of JointJS. Here are some of its features:. This library is used, for instance, in Draw. The library is developed since The mxGraph package contains a client software, written in JavaScript, and a series of backends for various languages.

The client software is a graph component with an optional application wrapper that is integrated into an existing web interface. The client requires a web server to deliver the required files to the client or can be run from the local filesystem without a web server. The backends may be used as is, or they may be embedded into an existing server application in one of the supported languages.

GoJS is a feature-rich JavaScript library for implementing interactive diagrams across modern browsers and platforms. GoJS makes constructing diagrams of complex Nodes, Links, and Groups easy with customizable templates and layouts. GoJS offers many advanced features for user interactivity such as drag-and-drop, copy-and-paste, transactional state and undo management, palettes, overviews, data-bound models, event handlers, and an extensible tool system for custom operations.

The API is very well documented to make sure you can start using in no time. We covered extensively GoJS in this post.