[wx-dev] [ wxwindows-Bugs-1816085 ] png under windows 98/2000 turn black

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Bugs item #1816085, was opened at 2007-10-18 21:15
Message generated for change (Comment added) made by moonkid
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Category: wxMSW specific
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: maxinuruguay (maxinuruguay)
Assigned to: Nobody/Anonymous (nobody)
Summary: png under windows 98/2000 turn black

Initial Comment:
Png shown by wxStaticBitmap will have the transparent parts turn black if any pixel in the png has an alpha value that is not 0 or 255.  If all the pixels have 0 or 255, the transparency works fine. The workaround is to go into photoshop an insure that all the png files are free of pixels that have in between alpha values. 

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Comment By: Christian Buhtz (moonkid)
Date: 2008-04-28 18:57

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The bug is still there on WinXPSP2 with wxStaticBitmap and wxTreeCtrl
items, etc.

Please see this picture
<ftp://ftp.berlios.de/pub/blackfisk/logo_alpha.png>
 
In the background is a big blackfisk. That is the SVG-Version I created
with "Inkscape". The background is set to transparent (Inkscape display it
white). 

In the right-top-corner you can see the exported PNG-file with the
transparent background (pink is transparent here because I setup the
viewing software that way). Each other SVG-viewing software (e.g. Opera)
display it correct with a transparent background. 

Then I try to use the exported PNG as a icon in a wxStaticText and
"import" with this line. 
wxwidgets:
wxBitmap(wxString::Format(_T("%s%s"), BF_GRAPHICDIR, _T("logo128.png")),
wxBITMAP_TYPE_PNG));

You can see the result in the right-middle in the picture. You see the
black background? Something is wrong here. 

My workaround is to load the PNG-file in IrfanView (a picture-viewer on
Win32) and re-save it with setting the transparent colour explicite in the
saving-options. 
Then it looks like the right-bottom picture. 

What is wrong here in this chain? I am not sure but I think wx did
something different or wrong while loading a PNG then other PNG-viewers
does. 
And I can say that storing transparency is handled different between
Inkscape and IrfanView.
________________
wxWdigets 2.9.x (SVN) build with MinGW as debug-dll on WinXPSP2 
Code::Blocks as IDE

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Comment By: Steven Van Ingelgem (g00fy)
Date: 2007-12-07 09:49

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I fixed this bug:
https://sourceforge.net/tracker/index.php?func=detail&aid=1761598&group_id=9863&atid=309863

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Comment By: deste (andreadestefani)
Date: 2007-12-07 09:46

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Thanks to maxinuruguay for submit this bug.

I want only to "update" this track and confirm what maxinuruguay have
already said. The problem with PNG alpha is present in win98/2000, not in
XP/Vista (don't know about MacOS and linux); the problem is present only
when use wxStaticBitmap (PNGs loaded in wxToolBar, or in wxMenu by
Menuitem->SetBitmap, or in wxListCtrl, works fine!).

Thanks to all wxDevs.


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