Learn Canvas in 10 Minutes

By Xah Lee. Date: . Last updated: .

Here's a simple canvas.

We paint a line, arc, text and rectangle.

Here's the HTML:

<canvas id="c89344" width="100" height="100"></canvas>

Here's the CSS, we just added a border:

canvas#c89344 {border:solid thin gray}

Here's the JavaScript:

{

const ff = (() => {

    const yy = document .getElementById("canvas47541");

    // create drawing area
    const xx = yy.getContext("2d");

    // paint a line
    xx.beginPath();
    xx.strokeStyle = "red"; // specify color
    xx.moveTo(0,0); // move pen to
    xx.lineTo(50,50); // draw line to here
    xx.stroke(); // actually draw it

    // paint a arc
    xx.beginPath();
    xx.strokeStyle = "blue";
    xx.arc(50,50, 30, 0, 2 * Math.PI, true); // x, y, radius, angle 1, angle 2, counter-clockwise
    xx.stroke();

    // paint a text
    xx.fillText("canvas", 0, 90,);

    // paint a rectangle
    xx.fillStyle = "cyan"; // specify color
    xx.fillRect(50, 25, 15, 10); // x, y, width, height

});

ff();

}

How to Script Canvas

To script HTML canvas, you create a canvas element, set a context (getContext("2d")), then use various drawing or style commands to paint the canvas area. That's about it.

Note that all canvas technology provides is a pixel painting area with JavaScript commands to paint it. It is not aware of what you drew. You can think of it as painting on a wall. For example, if you draw a circle, and you want to delete it, you have to draw on top to “cover” it. If you want to move the circle, you have to draw something to “cover” it, then draw another one at the place you want. If you want to detect clicks on the circle, you have to find the click's coordinate, then manually compute whether that coordinate is within the circle.

Canvas is in contrast with SVG. With SVG, every element you create is a object, and can be manipulated, move to front/back, change parameters, or be animated, put “onclick” event on it, and any changes are rendered in real-time. [see Canvas vs SVG]

Now, all you need to know about scripting canvas is the list of drawing commands.

You should know the basics of JavaScript.

[see JavaScript Basics]

HTML Canvas Reference

HTML Canvas Reference

HTML Canvas

  1. Canvas vs SVG
  2. Learn Canvas in 10 Minutes
  3. Canvas Tutorial: Halma Board Game
  4. HTML Canvas Demo: Raycaster
  5. HTML Canvas Reference

HTML Basics

  1. HTML Basics
  2. HTML5 Tags
  3. Case Sensitivity
  4. Allowed Characters
  5. Charset and Encoding
  6. Self-Closing Tags
  7. Multiple Class Value
  8. HTML Entity List

HTML Table

  1. HTML Table Examples
  2. HTML Table, thead, tbody, tfoot
  3. HTML Table, colgroup, col
  4. Styling HTML Table with CSS
  5. CSS: 3 Columns Page Layout
  6. Pure CSS Table

Misc

  1. Viewport Meta
  2. the Root Element
  3. iframe
  4. video
  5. audio
  6. figure
  7. dl, dt, dd
  8. s strike del
  9. time
  10. meter
  11. progress
  12. q
  13. address
  14. canvas
  15. ruby
  16. HTML5 Custom Data Attribute
  17. Big Tag
  18. Image Maps
  19. Marquee, Scrolling Text
  20. How to Markup Subtitle
  21. Meta Language Tag Obsolete
  22. Browser Auto Refresh

HTML4 Frameset

  1. HTML: Split Windows; Frameset
  2. HTML Nested Frameset
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