BlBlurBelowEffect not implemented

[LabordePierre]

Hi,

I'm looking for this effect:

Basically this is the capacity to setup a background to a shape, when the background is the back below with a blur effect.

I remember that a previous version of Bloc was implemented it. And @Nyan11 found the class BlBlurBelowEffect but appears not implemented in Alexandrie.

Particularly these methods: aeDrawBelow: aBlElement on: aeCanvas or aeDrawAbove: aBlElement on: aeCanvas as shadows effects.

[tinchodias]

In CSS there is backdrop-filter: blur(10px); (https://developer.mozilla.org/en-US/docs/Web/CSS/backdrop-filter)

[tinchodias]

Script to test it (after implemented):

BlSpace new
	extent: 500 asPoint;

	addChild: (BlElement new
		background: PolymorphSystemSettings pharoLogoForm asBlBackground;
		yourself);

		
	addChild: (BlElement new
		size: 100 asPoint;
		background: Color gray translucent;
		effect: (BlBlurBelowEffect new radius: 10; yourself);
		yourself);

	show.
``

[tinchodias]

Right now, we have AeCairoA8FastGaussianBlurFilter that is specialized on grayscaled images (1 channel only). This would require to extent it to RGB... we shouldn't expect high FPS if needs to be recalculated on each frame