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inverting colors of athens(cairo)canvas

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Peter Uhnak

inverting colors of athens(cairo)canvas

Is it possible to invert the colors of a Athens Canvas?

After some digging I found paintMode and paintTransform; however the former doesn't support such method (maybe some combination of xor and over?); and the former is only for some specific colors.

I also tried changing

Color>>asAthensPaintOn:

^ (Color white - self) alpha: (self alpha) "invert the color"

and while this works nicely for most cases, it is overriding a library and _doesn't_ work for bitmaps (for obvious reasons).

So is there some way how to invert it? Effectively a mask over the canvas. (Doing it at Morphic level should also be a viable option, provided it is possible there).

Thanks,

Peter

wernerk

Re: inverting colors of athens(cairo)canvas

Hi Peter,
at the morphic level you might eventually look at ColorMappingCanvas and
make a subclass.
werner

Nicolai Hess

Re: inverting colors of athens(cairo)canvas

2015-05-01 17:50 GMT+02:00 Werner Kassens <[hidden email]>:

Hi Peter,
at the morphic level you might eventually look at ColorMappingCanvas and make a subclass.
werner

Inverting the color of a form:

Display reverse:(0@0 extent:600@300).

Inverting colors of an athens drawing: Paint a white rectangle with paint mode "difference"

|view paint |
view := AthensSceneView new.
paint := nil.
view scene:[:canvas |
    paint ifNil:[paint := (Form fromDisplay:(0@0 extent:600@300) )asAthensPaintOn: canvas].
    canvas surface clear:Color white.
    canvas setPaint: paint.
    canvas drawShape:(0@0 extent:600@300).
    canvas paintMode restoreAfter:[
       canvas setPaint: Color white.
       canvas paintMode difference.
       canvas drawShape:(0@0 extent:600@300).
       ].
    ].
view openInWindow.

Peter Uhnak

Re: inverting colors of athens(cairo)canvas

Thanks Nicolai!

I should've tried all the paint modes before asking. -_-

Peter

On Fri, May 1, 2015 at 8:32 PM, Nicolai Hess <[hidden email]> wrote:

2015-05-01 17:50 GMT+02:00 Werner Kassens <[hidden email]>:
Hi Peter,
at the morphic level you might eventually look at ColorMappingCanvas and make a subclass.
werner

Inverting the color of a form:

Display reverse:(0@0 extent:600@300).

Inverting colors of an athens drawing: Paint a white rectangle with paint mode "difference"

|view paint |
view := AthensSceneView new.
paint := nil.
view scene:[:canvas |
    paint ifNil:[paint := (Form fromDisplay:(0@0 extent:600@300) )asAthensPaintOn: canvas].
    canvas surface clear:Color white.
    canvas setPaint: paint.
    canvas drawShape:(0@0 extent:600@300).
    canvas paintMode restoreAfter:[
       canvas setPaint: Color white.
       canvas paintMode difference.
       canvas drawShape:(0@0 extent:600@300).
       ].
    ].
view openInWindow.