Research: Transparency & hatch form in arc ring

[LinqLover]

No description provided.

[LinqLover]

Some findings:

• We could cache the basic shape of each arc ring in a Form
• When drawing it, we could render a rectangle first, reusing the usual Morph>>drawOn: implementation, and then use #image:at:sourceRect:rule:alpha: with rule Form and to limit the visible area (first and operand should be white for arc-ring pixels and transparent for all others). Don't know how many helper forms this requires.
• With this approach, custom effects, including transparency, should be possible.
• Furthermore, the cache might help us speed up the overall drawing.

Small example:

m := Morph new.
m extent: 256 @ 256.
m useGradientFill.
m fillStyle colorRamp at: 1 put: 0 -> (m fillStyle colorRamp first value  ccmWithAlpha: 0.5).

form1 := Form extent: m extent depth: 32.
form1 getCanvas fillOval: (0 @ 0 rect: form1 extent) color: Color white.
form1 getCanvas image: m imageForm at: 0 @ 0 sourceRect: (0 @ 0 rect: form1 extent) rule: Form and.
form1 openAsMorph.