an.stage.gradients#

Gradient fills on the stage: a Gradient drawn as an inline SVG texture.

The stage draws a gradient the way it already draws a glow (an#163): as ordinary document content – a data: SVG texture under a content-addressed alias, on an svg_sprite visual – not as a runtime feature. So runtime.js does not change, staging skips the inline source, and the bytes of the texture are a pure function of the gradient and its box.

Two boxes matter:

the box the sprite covers (a plane’s declared size, or the fill span that covers the canvas at any camera position), and
the frame the gradient is laid out over (the declared size, or the canvas): a gradient without a declared size is shaped by what the camera shows, and beyond the frame its end colours hold (SVG’s spreadMethod pad, CSS’s behaviour), so a pan never runs off the edge of the paint.

The SVG is rasterised at most GRADIENT_RASTER_MAX pixels on its longer side and stretched to the box – a smooth ramp loses nothing to that, and a 4000-pixel backdrop does not cost a 64 MB texture.

>>> from an.paint import Gradient
>>> svg = gradient_svg(Gradient(stops=["#000", "#fff"]), box=(100.0, 50.0), frame=(100.0, 50.0))
>>> svg.startswith('<svg xmlns="http://www.w3.org/2000/svg" width="100" height="50"')
True
>>> 'x1="50" y1="0" x2="50" y2="50"' in svg  # CSS's default: top to bottom
True

Module Attributes

GRADIENT_RASTER_MAX

The longest side, in texture pixels, a gradient is rasterised at.

Functions

`gradient_svg`(gradient, *, box, frame[, ...])	The SVG that paints `gradient` over `box`, laid out on the centred `frame`.
`gradient_src`(svg)	`svg` as the inline (`data:`) texture source the runtime loads.
`gradient_alias`(prefix, src)	A content-addressed texture alias: the same gradient, the same alias.

an.stage.gradients.GRADIENT_RASTER_MAX: int = 1024#: The longest side, in texture pixels, a gradient is rasterised at.

an.stage.gradients.gradient_alias(prefix, src)[source]#

A content-addressed texture alias: the same gradient, the same alias.

Return type:: str

>>> gradient_alias("glass.sky", "data:x") == gradient_alias("glass.sky", "data:x")
True

an.stage.gradients.gradient_src(svg)[source]#

svg as the inline (data:) texture source the runtime loads.

Return type:: str

an.stage.gradients.gradient_svg(gradient, *, box, frame, raster_max=1024)[source]#

The SVG that paints gradient over box, laid out on the centred frame.

Coordinates are scene pixels (the viewBox); width/height are the raster size, at most raster_max on the longer side.

Return type:: str

>>> from an.paint import Gradient
>>> svg = gradient_svg(Gradient(type="radial", stops=["#fff", "#000"]),
...                    box=(4000.0, 4000.0), frame=(1920.0, 1080.0))
>>> 'width="1024" height="1024"' in svg
True
>>> 'gradientTransform="translate(2000 2000) scale(960 540)"' in svg
True