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    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 Files

    #2
    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
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      #3
      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 Files
      Last edited by Noyb; 14.07.2007, 08:47 PM.

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        #4
        Seems to be working just fine here:
        Attached Files
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          #5
          And here too ... http://forums.techguy.org/digital-ph...ml#post4903539

          Wonder what I'm doing wrong ??

          Comment


            #6
            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.
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              #7
              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, 03:30 AM.
              Its: Belongs to "It"
              It's: Shortened form of "It is"
              ---------------------
              Lose: Fail to keep
              Loose: Not tight

              ---------------------
              Plurals do not require apostrophes

              Comment


                #8
                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, 02:32 AM.

                Comment


                  #9
                  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.
                  Its: Belongs to "It"
                  It's: Shortened form of "It is"
                  ---------------------
                  Lose: Fail to keep
                  Loose: Not tight

                  ---------------------
                  Plurals do not require apostrophes

                  Comment


                    #10
                    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, 12:32 PM.

                    Comment


                      #11
                      Thanks Ya’ll … Hummm .. I’m getting conflicting answers … or test results.
                      Seems like some can save a png from PS without any apparent IV viewing problems.
                      I’ve poked around in the PS CS2 options and can’t find any applicable settings.
                      Same with CS3.

                      In my original psd > png file .. White on Transparent .. Printed to a dark shirt just fine.
                      Someone else did this and I don’t know their procedures.
                      I originally converted to a gif - then the gif to png in PS.
                      This looked great on my end … but had some shirt printing problems.

                      If there’s nothing wrong with the png … Then why can’t IV see it correctly ?
                      I’ve looked in IV’s options and can’t find any settings to cure this.
                      I’ve tried 3.99 and 4.0 (with the gif fix) … and used two different Puters (processors)

                      My original problem is solved ... but several puzzles remain.
                      Windows Image n Fax viewer sees my png OK … Haven’t tried the Vista version yet.
                      Maybe this isn’t a bug in IV .. but can IV be made to work like I&FV.
                      I don’t believe I just said that … Please forgive my foul language :-)

                      Returno … You following along, is this helping any ??

                      Comment


                        #12
                        I searched in the options and its like matera said: Properties\Misc. 1\Show PNG alpha/transparent color. When I unchecked this option I got the same ugly appearance at your original downloaded PNG file. So we don't disagree on that matter. Would you let me know whether this is the solution?
                        Another question is which program you used to produce that gif file?
                        Last edited by Sjef; 15.07.2007, 04:18 PM.

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                          #13
                          Many Thanks ... That fixed it ... I missed that option in Misc 1

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                            #14
                            While working on a website header image today, I decided that I would consider the phenomenon as a feature. I said before that I haven't had any problems with the GIMP's PNG saving - but I seldom open a transparent PNG in non-transparent mode. When they all look all right, there's no problem in sight, right?

                            Attached are two screenshots of part of a transparent PNG that i made this morning with the GIMP. I opened it in MS Paint (the ultimate non-transparent editor LOL). The first shot shows that I screwed up and used a different background color after enlarging the canvas by a few pixels (the black edges). Then I "poured" black into the white part, and the subtle differences jumped out.

                            This image looks perfect in IV with transparency enabled, except for a couple of white pixels (feature! never would have seen them otherwise), but there are still blocks of slightly, invisibly different pixels. It only matters when transparency is not enabled. I think that with some variations in background/foreground colors and save settings, I could reproduce the Photoshop foibles.

                            I think that saving the color value of transparent pixels might have something to do with it...I don't know what PS has for options any more, it's been an age since I played with it. Next time I GIMP around I should take notes and experiment. I just want to know what does it, in case it matters for some touchy operation.
                            Last edited by matera; 25.10.2008, 03:30 AM.
                            Its: Belongs to "It"
                            It's: Shortened form of "It is"
                            ---------------------
                            Lose: Fail to keep
                            Loose: Not tight

                            ---------------------
                            Plurals do not require apostrophes

                            Comment


                              #15
                              I can only save transparent PNGs when the source is a transparent GIF.

                              I have no trouble saving transparent GIFs.

                              Therefore, I can't have transparent PNGs without converting my source (for example, I paint something in MS Paint and then select the entire surface and copy it directly to IrfanView) into a transparent GIF first.

                              Why it that?

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