2015-07-17 17:57 GMT+02:00 Aliaksei Syrel <[email protected]>:
> Hi
>
> Any ideas how one could blur an arbitrary shape using athens?
>
> Cheers,
> Alex
>
>
Not possible. Not with Athens and not with cairo. (There was a discussion
on cairos ml about drop shadows (and filter functions?, I am not sure) but
I don't think there is something like that currently).
Inkscape a vector/svg editor and viewer uses cairo but implements the svg
filter rendering on its own.
You can pre-render the cairo image and apply a filter function and use the
result as a form paint.
And you can cheat, and just compose multiple shape drawings with different
alpha values, but of course, this is slow:
| view star kernel s r root2pi |
s := 3.
r := 7.
root2pi := (2 * Float pi) sqrt.
kernel := (-1 * r to: r) collect: [ :i | 1 / (root2pi * s) * (-0.5 * (i
/ s) squared) exp ].
view := AthensSceneView new.
star := {32.0 @ 44.04868495317364.
13.458980337503156 @ 57.519524250561204.
20.541019662496844 @ 35.72324841040037.
1.999999999999993 @ 22.252409113012813.
24.917960675006306 @ 22.25240911301281.
31.999999999999993 @ 0.4561332728519787.
39.08203932499369 @ 22.252409113012803.
62.0 @ 22.252409113012803.
43.458980337503164 @ 35.72324841040037.
50.54101966249685 @ 57.5195242505612}.
view
scene: [ :canvas |
| path |
path := canvas
createPath: [ :builder |
builder
absolute;
moveTo: star first.
star allButFirstDo: [ :p | builder lineTo: p ].
builder close ].
canvas surface clear: Color white.
canvas paintMode over.
r negated to: r do: [ :i |
| a |
a := kernel at: r + i + 1.
r negated to: r do: [ :j |
| b |
b := a * kernel at: r + j + 1.
canvas setPaint: (Color black alpha: b).
canvas pathTransform
restoreAfter: [
| sx sy |
sx := canvas pathTransform sx.
sy := canvas pathTransform sy.
canvas pathTransform translateBy: (i / sx) @ (j
/ sy).
canvas drawShape: path ] ] ].
canvas pathTransform
restoreAfter: [
canvas pathTransform translateBy: (5 @ 5) negated.
canvas setPaint: Color red.
canvas drawShape: path ] ].
view openInWindow
