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hilaire

Scaled PNG image

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Stéphane Ducasse

Re: Scaled PNG image

On Nov 20, 2013, at 4:54 PM, Hilaire Fernandes <[hidden email]> wrote:

> Hello,
>
> In Pharo 2.0 (true in 1.4 as well), it looks PNG bitmap are wrongly
> rotated or scaled when they contain alpha transparency.
>
> In the example bellow with the joined bitmap, the alpha gray color are
> rendered darker when the imagemorph is scaled or rotated.
>
> Sqeak does not suffer this problem

hilaire may be you should have a look at the changes made in the graphics package
of squeak to identify the change.
We should have more tests.

Stef

>
>
> | dir morph transform form|
> dir := FileSystem disk workingDirectory parent.
> morph := (ImageReadWriter formFromFileNamed: (dir / 'bubble.png')
> fullName) asMorph.
> transform := TransformationMorph new asFlexOf: morph.
> transform smoothingOn ; angle: Float pi / 3; scale: 1.
> transform openInWorld
>
>
> Thanks
>
> Hilaire
>
>
> --
> Dr. Geo http://drgeo.eu
> <bubble.png>

hilaire

Re: Scaled PNG image

In reply to this post by hilaire

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Igor Stasenko

Re: Scaled PNG image

On 21 November 2013 14:22, hilaire <[hidden email]> wrote:

The problem is really not related to PNG bitmap as the same issue can be
exposed with simple, as in this example:

| morph rectangle |
rectangle := RectangleMorph new color: (Color red alpha: 0.5).
morph := TransformationMorph new asFlexOf: rectangle.
morph scale: 0.7.
morph openInWorld

In this example, the red appears darker once the rectangle is scaled.

Is it something related to the Blit ? I reallz don't know where to look.

no idea..

Except that while adopting cairo surfaces i also has odd transparency issues until i realized
that cairo surface stores pixel data using premultiplied alpha format,e.g.:

pixelColor = (R*A, G*A, B*A, A)

while bitblt assumes it is (R,G,B,A)

Hilaire

--
View this message in context: http://forum.world.st/Scaled-PNG-image-tp4723754p4723975.html
Sent from the Pharo Smalltalk Users mailing list archive at Nabble.com.

--
Best regards,
Igor Stasenko.

hilaire

Re: Scaled PNG image

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hilaire

Re: Scaled PNG image

In reply to this post by Stéphane Ducasse

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hilaire

Re: Scaled PNG image

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Igor Stasenko

Re: Scaled PNG image

In reply to this post by hilaire

On 21 November 2013 21:27, Hilaire Fernandes <[hidden email]> wrote:

Le 21/11/2013 08:21, Stéphane Ducasse a écrit :

>
> On Nov 20, 2013, at 4:54 PM, Hilaire Fernandes <[hidden email]> wrote:
>
>> Hello,
>>
>> In Pharo 2.0 (true in 1.4 as well), it looks PNG bitmap are wrongly
>> rotated or scaled when they contain alpha transparency.
>>
>> In the example bellow with the joined bitmap, the alpha gray color are
>> rendered darker when the imagemorph is scaled or rotated.
>>
>> Sqeak does not suffer this problem
>
> hilaire may be you should have a look at the changes made in the graphics package

I took at look on the list, did not find anything yet

not directly, right. But since symptoms are similar, i think this is most probably the same case.

(and your digging shown that we actually having separate rule for

premultiplied alpha blend, which i could use for correctly transferring/blending

cairo surface pixels in Forms)

Hilaire

> of squeak to identify the change.
> We should have more tests.
>
> Stef
>>
>>
>> | dir morph transform form|
>> dir := FileSystem disk workingDirectory parent.
>> morph := (ImageReadWriter formFromFileNamed: (dir / 'bubble.png')
>> fullName) asMorph.
>> transform := TransformationMorph new asFlexOf: morph.
>> transform smoothingOn ; angle: Float pi / 3; scale: 1.
>> transform openInWorld
>>
>>
>> Thanks
>>
>> Hilaire
>>
>>
>> --
>> Dr. Geo http://drgeo.eu
>> <bubble.png>
>
>
>

--
Dr. Geo http://drgeo.eu

--
Best regards,
Igor Stasenko.

Igor Stasenko

Re: Scaled PNG image

Yay, it works..

if i use:

canvas
        image: surface asForm
        at: bounds origin
        sourceRect: (0@0 extent: surface extent )
        rule: 34.

instead of

canvas translucentImage: surface asForm at: bounds origin.

hmm.. i just don't understand why:

image: aForm at: aPoint sourceRect: sourceRect rule: rule
"Note: The public use of this protocol is deprecated. It will become private. Nobody in the outside world must assume that a thing like a combination rule has any specific effect."

why it is considered private?
i wanna blend my form with another using specific rule,

and this is the only protocol available for that.. weird.

(Sorry for derailing topic, but that problem was quite annoying to me, i will take more deeper look at a fix later , and reply separately ;) )

On 22 November 2013 00:54, Igor Stasenko <[hidden email]> wrote:

On 21 November 2013 21:27, Hilaire Fernandes <[hidden email]> wrote:

Le 21/11/2013 08:21, Stéphane Ducasse a écrit :

>
> On Nov 20, 2013, at 4:54 PM, Hilaire Fernandes <[hidden email]> wrote:
>
>> Hello,
>>
>> In Pharo 2.0 (true in 1.4 as well), it looks PNG bitmap are wrongly
>> rotated or scaled when they contain alpha transparency.
>>
>> In the example bellow with the joined bitmap, the alpha gray color are
>> rendered darker when the imagemorph is scaled or rotated.
>>
>> Sqeak does not suffer this problem
>
> hilaire may be you should have a look at the changes made in the graphics package

I took at look on the list, did not find anything yet

not directly, right. But since symptoms are similar, i think this is most probably the same case.
(and your digging shown that we actually having separate rule for

premultiplied alpha blend, which i could use for correctly transferring/blending
cairo surface pixels in Forms)

Hilaire

> of squeak to identify the change.
> We should have more tests.
>
> Stef
>>
>>
>> | dir morph transform form|
>> dir := FileSystem disk workingDirectory parent.
>> morph := (ImageReadWriter formFromFileNamed: (dir / 'bubble.png')
>> fullName) asMorph.
>> transform := TransformationMorph new asFlexOf: morph.
>> transform smoothingOn ; angle: Float pi / 3; scale: 1.
>> transform openInWorld
>>
>>
>> Thanks
>>
>> Hilaire
>>
>>
>> --
>> Dr. Geo http://drgeo.eu
>> <bubble.png>
>
>
>

--
Dr. Geo http://drgeo.eu

--
Best regards,
Igor Stasenko.

--
Best regards,
Igor Stasenko.

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