rect-contain (demo)
Computes a transform between two rectangles the same way as
background-size: contain.
Intro
Simulating background-size: contain is very useful for canvas animations, drawing sprites in games, and rendering videos. This module is used as part of our video rendering pipeline at Automagical.
Install
Usage
Check out the demo to understand what this module does.
const {
scale,
translate
} = rectContain({ width: 500, height: 500 }, { width: 1280, height: 720 })
// CSS transforms apply the rightmost operation first.
// Note that this assumes a transform-origin of `top left`.
const transform = `translate(${translate.x}px, ${translate.y}px) scale(${scale})`
API
rectContain(viewport, image)
Returns a 2D affine transform defined by { scale: Number, translate: { x: Number, y: Number } } such that the given image will be fully contained within the viewport and also maintain its original aspect ratio.
Note that you'll want to apply the scale transform first followed by the translate.
viewport
Type: { width: Number, height: Number }
The viewport you want to draw the image into.
image
Type: { width: Number, height: Number }
The dimensions of the image to be drawn.
Related
- rect-cover is this module's sister, implementing
background-size: cover. - rect-crop if you need to mimic rect-cover with a
zoomratio andcenterpoint (eg, for kenburns effects) - css background-size
License
MIT (c) Travis Fischer
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