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Thread: PNG with transparent background issue

  1. #1

    Default PNG with transparent background issue

    I'm seeing an issue with incorrect rendering of a PNG with a transparent background. The same problem occurs with the last 3.x and also 4.0.

    I've attached two screen shots. One shows IrfanView's rendering, the other one shows the correct rendering using Windows Picture Viewer in WinXP SP2. Photoshop also shows the correct rendering. So, I think the bug belongs to IV.

    I can attach the problematic PNG itself if it would help, but it is easy to reproduce. I created this PNG - and 21 other ones that show the same bug - using Photoshop CS 8.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	irfan_png_bug1.JPG 
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ID:	50   Click image for larger version. 

Name:	win_pic_view_png.JPG 
Views:	622 
Size:	19.6 KB 
ID:	51  

  2. #2
    Moderator Enterprise User Bhikkhu Pesala's Avatar
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    This is not a bug. It depends on the background colour that you have currently set for Irfan View, which is black in your screen shot. Go to Options, Properties, Viewing, Main Window Colour, to change it to any colour you wish.

    /Mod: Moved from the bug report forum

  3. #3
    IV Beginner Noyb's Avatar
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    I don’t think that’s the solution … And it may even apply to Xnview.

    I have a gray on transparent logo created in Photoshop.
    the psd >> http://2noyb.home.insightbb.com/Sample.psd
    the png >> http://2noyb.home.insightbb.com/Sample.png

    When the png is viewed w M$ P&F .. or Office Picture Manger it looks OK.

    When saved as a png from PSCS2 or CS3 or PSE 5.0 .. this is what it looks like.

    In Photoshop >> in Irfanview (or Xnview) as a png.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Sample.jpg 
Views:	356 
Size:	7.4 KB 
ID:	52   Click image for larger version. 

Name:	Sample2.jpg 
Views:	434 
Size:	5.1 KB 
ID:	53  
    Last edited by Noyb; 14.07.2007 at 07:47 PM.

  4. #4
    Moderator Enterprise User Bhikkhu Pesala's Avatar
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    Seems to be working just fine here:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	White Window.png 
Views:	428 
Size:	17.0 KB 
ID:	54   Click image for larger version. 

Name:	Black Window.png 
Views:	397 
Size:	17.2 KB 
ID:	55   Click image for larger version. 

Name:	Grey Window.png 
Views:	377 
Size:	17.0 KB 
ID:	56  

  5. #5
    IV Beginner Noyb's Avatar
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    And here too ... http://forums.techguy.org/digital-ph...ml#post4903539

    Wonder what I'm doing wrong ??

  6. #6
    Moderator Enterprise User Bhikkhu Pesala's Avatar
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    Quote Originally Posted by returno View Post
    I can attach the problematic PNG itself if it would help, but it is easy to reproduce.
    Yes, you need to attach a sample PNG file.

  7. #7
    Advanced User matera's Avatar
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    It's the option to show PNG alpha transparency that is throwing some of you guys off the trail. I cownloaded the sample logo pics. With transparency on, IV shows it just fine. Transparency off, and it's a mess. IV shows the PSD all right. I think some Photoshop setting needs to be tweaked. I used 11view to decompile the PSD (I don't have Photobloat installed, and I was looking for a PSD to test that feature!). It created six bitmaps that show where some of the gray blocks seem to come from. There seems to be something amiss with the layer blending/flattening - whatever it wants to call it.

    I made screenshots to illustrate, Transparency off, transparency on, and the decompiled PSD BMPs in IV's thumbviewer.
    Last edited by matera; 25.10.2008 at 02:30 AM.

  8. #8
    IV Beginner Noyb's Avatar
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    You gave me a clue .. TX
    Simple psd’s don’t seem to have this problem.
    The sample psd was created with test and graphics layers and layer effects to create this problem.

    Poking around in CS2, I found … Help > Export Transparent Image.
    .... Who would have thought to look there ???
    All the layers must be flattened (merged) before using this tool.

    This procedure seems to have fixed the png problem … for Irfanview.

    I’ve tried to flatten the layers before “saving as” png previously .. but this didn’t work.
    Still curious why some viewers, or Irfan's thumbs, don't have this problem.
    Last edited by Noyb; 15.07.2007 at 01:32 AM.

  9. #9
    Advanced User matera's Avatar
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    I'll leave that mystery for another cybersherlock to solve. I use the GIMP, and so far it hasn't left any ghostly artifacts.

    MS Paint shows the ugly blocks too. Anything that doesn't handle PNG transparency might, I think. It must be a case of partial transparency, which would not show in transparent mode but goes totally opaque when transparency is not allowed.
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  10. #10
    Moderator Sjef's Avatar
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    I have saved your psd sample to png, without (of course) merging the layers. The result was a fine viewable png (which it should be). My Photoshop works with as much standard-option as possible. For every layer whithin your psd-image there's an invisable alpha-layer enclosed to cover up the backgrounds of the rounded textlayers and the dog-layer. Depending on the options you've checked in your viewer(s), every today's viewer I know can show your png file, even object-orientated programs like Xara. So you'd better look into that matter (the viewer-options), because there's nothing wrong with your png file Photoshop has produced.
    Last edited by Sjef; 15.07.2007 at 11:32 AM.

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