canvas-animation-loader
v0.0.5
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webpack loader for canvas animations
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canvas-animation-loader lets you hardware accelerate your canvas animations.
It converts a javascript file that exports an icon class into a static SVG,
with one panel for each frame of the animation. This lets you run the animation
on the GPU using CSS's translateX()
transform with a step()
parameter.
Installation
npm install --save-dev canvas-animation-loader
Usage
First create a javascript file that exports an animated icon class:
export default class SearchIcon {
constructor(duration, width, height) {
// configure your renderer to produce an animation of the given size
// when render is called.
// in the default configuration animations last for 166 milliseconds and
// are 32x32pixels.
}
render(context, time) {
// context is obtained from a canvas element's .getContext('2d'),
// time is the point in time that the animation should render at.
// In the default configuration this method will be called 11 times
// at 16.6ms intervals (60 frames per second), e.g. with values:
// [0, 16.6, 33.2, 49.8, 66.4, 83, 99.6, 116.2, 132.8, 149.4, 166]
}
}
module.exports = class SearchIcon
constructor: (@duration, @width, @height) ->
render: (context, time) ->
# draw your animation to the canas as it should appear at time T.
Then use it as a background image on some HTML in this configuration:
<div class="animation-viewPort">
<div class="animation-slider"/>
</div>
And load the image into CSS thusly:
.animation-viewPort {
width: 32px;
height: 32px;
overflow: hidden;
}
.animation-slider {
width: calc(32px * 11);
height: 32px;
background-image: url(~!url-loader?mimeType=image/svg+xml!val-loader!canvas-animation-loader!./search_icon.js);
// transform one less than the number of frames so that the last
// frame is visible in the viewport.
transform: translateX(calc(-32px * 10));
// show ten frames, each one lasts for 16.6ms (which is a rounded approximation of 1/60, so 60 frames per second)
transition: transform 166ms step(10);
}
.animation-slider:hover {
// cause the animation to move to the other end.
transform: translateX(0);
}
Options
There are four configurable parameters to the loader, each of which is determined by the values in your CSS (or vice-versa).
url(~!url-loader?mimeType=image/svg+xml!val-loader!canvas-animation-loader?width=X&height=X&duration=X&interval=X);
- width (32) — the number of pixels wide your icon expects to be (passed into the constructor)
- height (32) — the number of pixels tall your icon expects to be (passed into the constructor)
- duration (166) — the number of milliseconds your animation will run for (passed into the constructor)
- interval (16.6) — the number of milliseconds between each frame (render will be called duration/interval + 1 times)
To make all this work in the CSS:
- The width and height of the viewport should be set to the width and height of each frame.
- The height of the slider should be the same as the height of the viewport.
- The width of the slider should be the width of each frame * (duration/interval + 1).
- The initial transform should be
translateX(-(duration/interval) * frame width)
. - The final transform should be
translateX(0px)
.