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ColorForm with transparency not working properly

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Christoph Thiede

ColorForm with transparency not working properly

Hi all,

try out this:

m := Morph new color: (Color red alpha: 0.5).

m openInHand.

m imageForm openAsMorph.

Output:

And for completeness' sake, "m imageForm asMorph imageForm openAsMorph" appears just a bit darker again.

I traced the issue down to two methods: For the regular Morph, FormCanvas >> #setFillColor:, and for the ImageMorph, Canvas >> #translucentImage:at:sourceRect:. In both methods, at the end, the rule Form blend is used to draw the image. If I change it to Form over, the colors are the same and the issue seems to be fixed.

But unfortunately, I could not find any documentation about the different Form rules such as #blend, #over, #paint etc. Can you give me some pointers?

Also, I noted the comment in #translucentImage:at:sourceRect: which states:

"Draw a translucent image using the best available way of representing translucency.

Note: This will be fixed in the future."

Which workaround is this comment referring to?

Looking forward to your help! :-)

Best,

Christoph

Carpe Squeak!

Stéphane Rollandin

Re: ColorForm with transparency not working properly

> But unfortunately, I could not find any documentation about the
> different Form rules such as #blend, #over, #paint etc. Can you give me
> some pointers?
Related thread:
http://forum.world.st/ImageForm-color-with-alpha-td5090574.html

Stef

Christoph Thiede

Re: ColorForm with transparency not working properly

Thanks for the pointer, Stef. I think we really need some kind of documentation of the form rules to decide whether we can apply Marcel's solution. Did anyone ever read something about it?

Best,

Christoph

Von: Squeak-dev <[hidden email]> im Auftrag von Stéphane Rollandin <[hidden email]>
Gesendet: Samstag, 19. September 2020 22:34:21
An: [hidden email]
Betreff: Re: [squeak-dev] ColorForm with transparency not working properly

Carpe Squeak!

Karl Ramberg

Re: ColorForm with transparency not working properly

It is this code that apply the blendAlphaScaled.

BalloonEngine>>bitBlt: aBitBlt

| destWidth |
bitBlt := aBitBlt.
bitBlt isNil ifTrue:[^self].
destWidth := bitBlt destForm width.
destWidth > span size ifTrue:[span := Bitmap new: destWidth].
self class primitiveSetBitBltPlugin: bitBlt getPluginName.
self clipRect: bitBlt clipRect.
bitBlt
sourceForm: (Form extent: span size @ 1 depth: 32 bits: span);
sourceRect: (0@0 extent: 1@span size);
colorMap: (Color colorMapIfNeededFrom: 32 to: bitBlt destForm depth);

combinationRule: (bitBlt destForm depth >= 8 ifTrue:[34" blendAlphaScaled "] ifFalse:[Form paint]).

Best,

Karl

On Mon, Sep 21, 2020 at 9:31 PM Thiede, Christoph <[hidden email]> wrote:

Thanks for the pointer, Stef. I think we really need some kind of documentation of the form rules to decide whether we can apply Marcel's solution. Did anyone ever read something about it?

Best,

Christoph

Von: Squeak-dev <[hidden email]> im Auftrag von Stéphane Rollandin <[hidden email]>
Gesendet: Samstag, 19. September 2020 22:34:21
An: [hidden email]
Betreff: Re: [squeak-dev] ColorForm with transparency not working properly

> But unfortunately, I could not find any documentation about the
> different Form rules such as #blend, #over, #paint etc. Can you give me
> some pointers?
Related thread:
http://forum.world.st/ImageForm-color-with-alpha-td5090574.html

Stef

Karl Ramberg

Re: ColorForm with transparency not working properly

See also mail from Juan Vuletich in vm-dev list:"Proposal for new BitBlt rules (#505)" which has fixes for alpha blending

Best,

Karl

On Mon, Sep 21, 2020 at 9:44 PM karl ramberg <[hidden email]> wrote:

It is this code that apply the blendAlphaScaled.

BalloonEngine>>bitBlt: aBitBlt
| destWidth |
bitBlt := aBitBlt.
bitBlt isNil ifTrue:[^self].
destWidth := bitBlt destForm width.
destWidth > span size ifTrue:[span := Bitmap new: destWidth].
self class primitiveSetBitBltPlugin: bitBlt getPluginName.
self clipRect: bitBlt clipRect.
bitBlt
sourceForm: (Form extent: span size @ 1 depth: 32 bits: span);
sourceRect: (0@0 extent: 1@span size);
colorMap: (Color colorMapIfNeededFrom: 32 to: bitBlt destForm depth);
combinationRule: (bitBlt destForm depth >= 8 ifTrue:[34" blendAlphaScaled "] ifFalse:[Form paint]).

Best,
Karl

On Mon, Sep 21, 2020 at 9:31 PM Thiede, Christoph <[hidden email]> wrote:

Thanks for the pointer, Stef. I think we really need some kind of documentation of the form rules to decide whether we can apply Marcel's solution. Did anyone ever read something about it?

Best,

Christoph

Von: Squeak-dev <[hidden email]> im Auftrag von Stéphane Rollandin <[hidden email]>
Gesendet: Samstag, 19. September 2020 22:34:21
An: [hidden email]
Betreff: Re: [squeak-dev] ColorForm with transparency not working properly

> But unfortunately, I could not find any documentation about the
> different Form rules such as #blend, #over, #paint etc. Can you give me
> some pointers?
Related thread:
http://forum.world.st/ImageForm-color-with-alpha-td5090574.html

Stef

Karl Ramberg

Re: ColorForm with transparency not working properly

In reply to this post by Christoph Thiede

Class comment for VMMaker-Interpreter/BitBltSimulation

 has some information. This information is not in the image currently.


This class implements BitBlt, much as specified in the Blue Book spec.

Performance has been enhanced through the use of pointer variables such as sourceIndex and destIndex, and by separating several special cases of the inner loop.

Operation has been extended to color, with support for 1, 2, 4, 8, 16, and 32-bit pixel sizes.  Conversion between different pixel sizes is facilitated by accepting an optional color map.

In addition to the original 16 combination rules, this BitBlt supports
	16	fail (for old paint mode)
	17	fail (for old mask mode)
	18	sourceWord + destinationWord
	19	sourceWord - destinationWord
	20	rgbAdd: sourceWord with: destinationWord
	21	rgbSub: sourceWord with: destinationWord
	22	OLDrgbDiff: sourceWord with: destinationWord
	23	OLDtallyIntoMap: destinationWord -- old vers doesn't clip to bit boundary
	24	alphaBlend: sourceWord with: destinationWord
	25	pixPaint: sourceWord with: destinationWord
	26	pixMask: sourceWord with: destinationWord
	27	rgbMax: sourceWord with: destinationWord
	28	rgbMin: sourceWord with: destinationWord
	29	rgbMin: sourceWord bitInvert32 with: destinationWord
	30	alphaBlendConst: sourceWord with: destinationWord -- alpha passed as an arg
	31	alphaPaintConst: sourceWord with: destinationWord -- alpha passed as an arg
	32	rgbDiff: sourceWord with: destinationWord
	33	tallyIntoMap: destinationWord
	34	alphaBlendScaled: sourceWord with: destinationWord
	35 alphaBlendScaled: sourceWord with:	"unused here - only used by FXBlt"
	36 alphaBlendScaled: sourceWord with:	"unused here - only used by FXBlt"
	37 rgbMul: sourceWord with: destinationWord
	38 pixSwap: sourceWord with: destinationWord
	39 pixClear: sourceWord with: destinationWord
	40 fixAlpha: sourceWord with: destinationWord
	41 rgbComponentAlpha: sourceWord with: destinationWord

This implementation has also been fitted with an experimental "warp drive" that allows abritrary scaling and rotation (and even limited affine deformations) with all BitBlt storage modes supported.

To add a new rule to BitBlt...
	1.  add the new rule method or methods in the category 'combination rules' of BBSim
	2.  describe it in the class comment  of BBSim and in the class comment for BitBlt
	3.  add refs to initializeRuleTable in proper positions
	4.  add refs to initBBOpTable, following the pattern

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On Mon, Sep 21, 2020 at 9:31 PM Thiede, Christoph <[hidden email]> wrote:

Thanks for the pointer, Stef. I think we really need some kind of documentation of the form rules to decide whether we can apply Marcel's solution. Did anyone ever read something about it?

Best,

Christoph

Von: Squeak-dev <[hidden email]> im Auftrag von Stéphane Rollandin <[hidden email]>
Gesendet: Samstag, 19. September 2020 22:34:21
An: [hidden email]
Betreff: Re: [squeak-dev] ColorForm with transparency not working properly

> But unfortunately, I could not find any documentation about the
> different Form rules such as #blend, #over, #paint etc. Can you give me
> some pointers?
Related thread:
http://forum.world.st/ImageForm-color-with-alpha-td5090574.html

Stef

Christoph Thiede

Re: ColorForm with transparency not working properly

Thanks, Karl.

Still, I do not see what the combination rules are good for. For example, my
image does not implement #alphaBlend:with:.

Here is another request for some documentation of the combination rules:
https://github.com/MrModder/Autocompletion/issues/36

Best,
Christoph

--
Sent from: http://forum.world.st/Squeak-Dev-f45488.html

Carpe Squeak!