[Gambas-user] Pb with transparency?

[Simonart Dominique]

Benoît Minisini a écrit :
>> Benoît Minisini a écrit :
>>>> Hi,
>>>>
>>>> Gambas 2.12 with QT
>>>>
>>>> I had a prog that worked well in Gambas 2.11 but now it
>>>> doesn't work correctly for all the images with transparent
>>>> areas.
>>>> Here is a very short illustration of the problem
>>>>
>>>> DIM PicSac AS Picture
>>>> DIM PicCase AS Object[]
>>>> Dim i AS Integer
>>>>
>>>> PicCase.Resize(2)
>>>> FOR i = 0 TO 1
>>>>     PicCase[i] = NEW Picture(14, 14, TRUE)
>>>> NEXT
>>>> PicCase[0] = Picture.Load(image with some transparent part)
>>>> PicCase[1] = Picture.Load(image without transparent area)
>>>>
>>>> PicSac = NEW Picture(14, 14, TRUE)
>>>> i = 0
>>>> Draw.Begin(PicSac)
>>>> Draw.Picture(PicCase[i], 0, 0, 14, 14, 0, 0, 14, 14)
>>>> Draw.End
>>>>
>>>> PictureBox1.Picture = PicSac
>>>>
>>>> i = 0 => nothing displayed
>>>> i = 1 => correct display
>>>> (I know that Gambas 2.12 changed the Draw routine)
>>>> Is it a bug?
>>>>
>>>> regards,
>>>> Dominique Simonart
>>> I will look at that.
>>>
>>> Beware that the Picture class is not really transparent. It has no alpha
>>> channel but a bitmap mask.
>>>
>>> Creating a "transparent" Picture internally creates an X11 pixmap and a
>>> X11 bitmap mask. Drawing on it the must update both the pixmap and the
>>> mask. I think that the mask update is buggy for the Draw.Picture()
>>> method.
>>>
>>> Anyway, you should use the Image class and its Draw method to draw an
>>> image on top another one with real alpha transparency.
>>>
>>> To add to the complexity, converting an Image to a Picture keeps the
>>> alpha information with gb.qt, but not with gb.gtk. This is a Qt feature,
>>> that uses the XRender extension for that. But GTK+ don't, and just
>>> removes all pixels whose alpha component is lower than 128. But you
>>> should not take that into account as it is really toolkit specific.
>>>
>>> Regards,
>> Thanks Benoit,
>> I replaced PicCase[] and PicSac by Image and used Draw
>> method instead of Draw.Begin(...).
>> The last instruction is now:
>> PictureBox1.Picture = PicSac.Picture
>>
>> Here are the results:
>> 1) i=0 now display correctly the image with transparent part
>> 2) If I use 2 buttons to draw with i=0 (button1) and i=1
>> (button2)
>> *   button1 then button2 display correctly the two images
>> successively
>> * button2 then button1 display only the image without
>> transparent part (button1 didn't change the display)
>> * if I replace Image1 with another image without transparent
>> part I could see the images associated with their buttons
>>
>> In conclusion, as soon as there is a transparent part in my
>> image, it could never override another image
>>
>> Hope this helps
>> Dominique Simonart
>>
> 
> I fixed many bugs in Draw.Picture() and Draw.Image() in revision #1938, both 
> for gb.qt and gb.gtk. Can you try it to check if you have the same problems?
> 
> Regards,
> 

Hi Benoit,

I'm sorry Benoit, but I don't install Gambas from svn, I use 
the rpms built by Guillermo Ballester Valor for OpenSuse 
(gambas 2.12-3.7). I don't know the revision level I'm using.

regards,
Dominique Simonart