black color issue for PNG

[.nos.]

Hi,
I noticed an issue concerning 32bits PNG files.
It looks like pictures in this format actually uses the color set in "Options/View/Background color" instead of the black color.
means if you leave this option to grey (default), you'll get grey instead of black in the whole picture. if you set black, you'll get black as expected.
This is also true for the thumbnails view and preview with their respective background color

Tested with XnView 1.92 (19 dec 2007)

[Clo]

Hello !

• Please, try to tick the box in:

–> View Menu >> Use Alpha Channel

KR
Claude
Clo

[Guest]

Use alpha channel was already checked;
But if I uncheck it, those 32bits PNG files are then displayed properly; thx for the tips.
only left the thumbnails view, where I can't find this option, so you still see the transparent objects in the picture with the thumbnails background color...

possibly I'm wrong, but looks like to me that Use alpha channel option works in the opposite way.

[Clo]

.nos.

Hello !

• Strange, here the option in the menu works normally…
- If I untick it, then the BG is black…

- You can use too the option (F12) >> View [×] Use chequered pattern… or so to replace the transparency.
- The colour depth you set for display in Win does matter too, here I've 16 BPP only,
and I can't see the transparency in the thumbnails (black BG), the chequered pattern is not applied,
while it's in the Preview of the browser…

KR
Claude
Clo

[xnview]

Use alpha channel was already checked;
But if I uncheck it, those 32bits PNG files are then displayed properly; thx for the tips.
only left the thumbnails view, where I can't find this option, so you still see the transparent objects in the picture with the thumbnails background color...

possibly I'm wrong, but looks like to me that Use alpha channel option works in the opposite way.

Could you post the png picture used?

[.nos.]

Hi, sure I can
I've used ImageShack; should you have better solution, let me know.



you should see the creature on the bottom left transparently; but even the browser show it in plain white...and some nasty bugs with the chains hanging from the ceiling.

[XnTriq]

It's another mangled game/video screenshot.

Recommended settings:

• View »
  • » Use alpha channel » On
    » Show Mask » Off
• Tools » Options... »
  • » General » Read/Write » PNG » Parameters » Compose image with transparency » Off
    » General » Read/Write » PNG » Parameters » Compose image with alpha (32bits) » Off
    » View » View » Background colour » R128/G128/B128
    » View » View » Use checkerboard pattern as background » On
    » View » Fullscreen » Background colour » R128/G128/B128

See also:

• stdin | stdout
• BMP color index
• 32 bit BMP problems when transparent index enabled (v1.91)
• BMP files viewing is bugged
• File opens in Internet Explorer - Firefox but not in XnView
• Targa isnt displaying correctly; lots of flat grey
• 1.91.5: Can't handle some BMP images
• screen shots

[.nos.]

Ok, I was suspecting the screenshot was mangled; but as far as I remember, it was allright with my previous version of xnview (1.82)

Anyway, the point is that I can't use your setting to see them properly; I've got to set View > use alpha channel to off.
besides, I've to set View > Preview > use alpha channel to off in order to display a proper preview, and lastly, I've to rebuild the thumbnails to show them with the right transparency. thx to the links you posted, I didn't know this command