I moved this to a separate page to keep this article short and so I only have to update it in one place. You can get all the code from this tutorial on the repository below.
Some quick bullet points to introduce you to the canvas. When working with a canvas there are five steps to get started.
This has several benefits such as preventing players if this were a game from accessing your variables directly and prevents your code from colliding with someone else's code such as a library or another script on the website. By default, the coordinate system starts at the top left. X: 0, Y: 0 Moving down or to the right increases X and Y positions.
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You can play with the example below on this page. Feel free to reference the documentation page at any time. There will also be a link to each method we use. To do that, we will make a function to handle the setup process we did above and listen for the DOMContentLoaded event. We will call this function init for initialize. Remember: everything stays inside the IIFE wrapper. If you ever get lost refer to the completed project here.
We want our canvas and context variables to be available to all of our functions. This requires defining them up top and then giving them a value in the init function once the DOM loads. This completes our setup. Note : A more scalable option is to accept the context variable as an argument to our drawing functions. Inside of our init function, we use context2D. On the next line, we create and draw a rectangle a square in this case.
There are two different methods we use to draw the path to the screen:. Stroke is the same thing as an outline or border. The Result:. There are a few things to note here:. But wait… we want a fill AND a stroke, does this mean we have to draw two squares? You can draw two squares but we will make use of several other methods instead. It creates a path for the square in memory, we then configure the stroke, fill, and stroke width before calling ctx. Drawing any shape always follows these steps:.Comments are for users to ask questions, collaborate or improve on existing.
HTML5 canvas draw line tutorial - Change width and color. In this tutorial we are going to review how to draw a line, change line widths, change line color, join two lines, define a line cap, etc.
If you are not familiar with the HTML5 canvas and its 2d context please review the beginners tutorial - HTML5 canvas tutorial for beginners CANVAS 2d context methods and attributes that are used in this tutorial beginPath The beginPath method clears the current path and specifies the beginning of a new path moveTo x,y The moveTo method moves the path to the specified point x,y in the canvas, without creating a line lineTo x,y The lineTo method creates a line from the path's current point to the specified point x,y in the canvas stroke The stroke method paints the current path, with the color set by the strokeStyle attribute, black is default strokeStyle color of the drawing, black is default.
Available choices are butt, round and square.
The first idea that may strike you is to generate a serie of DIV of 1px per 1px to draw the line. It works, it's dead simple and extremely short. Alas it's slow and generates a hell lot of useless tags, not to mention the difficulty to move a line. Of course it can be optimized a bit using some Bresenham line algorithms and making use of symetry, etc The key to get a fast script, is to do the minimum.
Trying to figure the common factors of the lines we saw above will lead us in that direction. Try to project mentally the lines on the small edge of their bounding box. It should ring a bell. Any line can be reproduced by stretching a diagonal. If you need more to be convinced, just look the figure below. So what we need is to figure the width and height of the bouding box, and the direction of the line and size of the small edge.
Both things can be considered if we only use some diagonnals whose size is a power of 2, that is : 1, 2, 4, 8, 16, 32, 64, Ok, it will introduce some small stretching artifacts but that's a small price to pay to move the lines in realtime. Getting the position of the bounding box and the size of its smaller edge is staight forward.
Calculating the direction of the line corresponds more or less to compute in which quadrant of a circle it is pointing. Pixel perfect precision can be achieved at the price of having all possible diagonals.
It takes a lot more time, and connections, to preload the images but the end result look nicer and is slightly faster than the quirk method above. The number of applications is endless: route annotations on maps, drawing app, measuring tool, games, Don't be shy; get in touch by mailtwittergithublinkedin or pouet if you have any questions, feedback, speaking, workshop or performance opportunity.It is renderer agnostic enabling the same api to draw in multiple contexts: svgcanvasand webgl.
Development Version Uncompressed with comments about kb. Production Version Minified using Closure Compiler about 50kb. Prior to v0. If you're already loading these files elsewhere then you can build the project yourself and get the file size even smaller. For more information on custom builds check out the source on github. As a result, two.
At its core two. This means that when you draw or create an object a Two. Path or Two. Grouptwo actually stores and remembers that. After you make the object you can apply any number of operations to it — e. It is simple in nature and can be automated or paired with another animation library. For more information check out the examples. This means developers and designers alike can create SVG elements in commercial applications like Adobe Illustrator and bring them into your two.
In order to start any of these demos you'll want to download two. When you visit the page, you should be able to open up the console and type Two. If this returns a function then you're ready to begin! Before we get into all the fancy animating it's good to get a feel for how to make shapes in two.
In order to do this we need to have an instance of two. This sets up a dom element that contains either an svg or canvas element to add to the webpage.
The two object has a scene which holds all shapes as well as methods for creating shapes. For a list of all properties and construction parameters check out the documentation. Adding shapes to groups makes managing multiple shapes easier and more sane.
Group's provide an easy way to move your content through translationrotationand scale. These operations emit from the coordinate space 0, 0. In the example below we can see that the initial orientation of the circle and rectangle changed from the first example. These shapes are oriented around 0, 0which allows us to transform the group around the centeroid of the shapes. In addition Group's styling operations trickle down and apply to each shape.
All rendered objects in two. Every two instance has a property scene. This property is a root-level Two. Group and can act as a camera through the same transformations described above. Finally, let's add some motion to our shapes. So far the examples use two. The instance of two. The first is two.How do you draw a line on a computer screen without canvas or libraries? Do you ever have a project you always lay off for later?
Well, drawing a line in HTML without canvas was something on my mind for over a year.
And I finally decided to make this tutorial on the subject! By the way you can follow me on Twitter for more freemium tutorials. Check out this line drawing demo live in action on a sample page I created. The above is the result of the algorithm explained in this tutorial. A line is drawn between two points on a typical raster display. How would something like this work?
I created this demo screenshot to show the basic idea in action. Given any two end points — we can render a line on a raster display. While the algorithm for Quadrant 1 is simple — implementation for all quadrants and octants is tricky. But only logistically. The rest of the cases are simple mirror images of the two octants in Quadrant 1.
This means that instead of reinventing the wheel all you have to do is swap some variables around or flip their sign here and there. You can spawn as many as you like. I come from a game development background. And in games you often deal with drawing lines. Of course, raw HTML rendering speed will be an issue. And yes, further optimizations will be required to achieve meaningful performance. But the focus of this line drawing tutorial is primarily set on the line drawing algorithm explanation itself.
You can always re-implement it in any other raster environment or graphics library. We take two deltas and calculate the slope of the line equation, based on two end points of the line.
To complete the algorithm, we must also adjust parameters based on what octant out of eight we are in. This is explained in detail in the following section. But we need to cover all directions.
Drawing lines examples with Java Graphics2D
But the basic idea is there. The main if-statement branches out between two potential axis-dominance cases.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.
Around —, Mozilla started work on an experimental 3D canvas implementation. 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.
Code Review Stack Exchange is a question and answer site for peer programmer code reviews. It only takes a minute to sign up. I just started trying out SVG the other day. Eventually I hope to be able to know how to do what SE does with their reputation graphs. For now, I've just been trying to set up an easier way to make lines. I think my below code is decent, but please let me know what I can improve on or what I'm doing poorly. If you are going to do animations with those lines, you will want to keep track of them.
However, in createLine you create the SVG element and just return it, you do not keep a reference to it. So it will be hard to animate those lines, you would have to query the DOM to find them back.
I suggest you have an object that creates SVG elements, a factory so to speak.
And then another object that tracks lines you have created so far, mostly to do animations and other fun stuff. Sign up to join this community. The best answers are voted up and rise to the top.
Home Questions Tags Users Unanswered. Asked 6 years, 2 months ago. Active 3 years, 5 months ago. Viewed 22k times. Would like your thoughts before I start adding like animations, creativity, data to it.
That library has a very nice way of handling 2D rendering.