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Learning <canvas>

Just one of the things I'm learning. https://github.com/hchiam/learning

Canvas vs SVG

https://www.sitepoint.com/canvas-vs-svg-choosing-the-right-tool-for-the-job/

SVG = visual scalability but more DOM memory.

Canvas = "paint-and-forget" less DOM memory but raster instead of ability to do vector scaling.

You can even combine SVG and canvas.

Canvas vs WebGL

WebGL uses <canvas>. WebGL tutorial: https://developer.mozilla.org/en-US/docs/Web/API/WebGL_API/Tutorial

Tutorial

https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial

Rectangles

var canvas = document.getElementById('tutorial');
var context = canvas.getContext('2d');
context.strokeStyle = 'rgba(...)';
context.fillRect(x, y, w, h);
context.clearRect(x, y, w, h);
context.strokeRect(x, y, w, h);

Paths

var canvas = document.getElementById('tutorial');
var context = canvas.getContext('2d');
context.stroke() // to draw line shape
context.fill(...) // to draw filled shape
context.beginPath(...) // !
context.closePath()
context.moveTo(...)
context.lineTo(...)
context.bezierCurveTo(...)
context.quadraticCurveTo(...)
context.arc(...)
context.arcTo(...)
context.ellipse(...)
context.rect(...)
...

Note: Path2D object is like a "macro" that "records" paths that you can play back quickly. It is NOT currently available in IE.

Transformations

Clipping paths

Everything after it will only show up inside the clipping path.

Animation

https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Basic_animations

  1. clear canvas context.clearRect(x, y, w, h);
  2. (save state of canvas (if you want to reuse it each frame) context.save();)
  3. draw
  4. (restore state of canvas (before the next frame, if you already want to save state) context.restore();)

https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Advanced_animations

Pixel manipulation

https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas

Examples:

Hit regions (currently experimental)

https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Hit_regions_and_accessibility

Perf tips

https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Optimizing_canvas