Bug: PNG transparency showed with artefacts

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Micha
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Bug: PNG transparency showed with artefacts

Post by Micha » Thu Nov 20, 2008 1:38 pm

Hello,

since a long time seen here - the transparency of PNG is showed wrong at XnView. Here an extrem example: XnView show a quadrat, but the image should show a black disk.

Good luck for fixing.

Thanks,
Micha

Image

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Re: Bug: PNG transparency showed with artefacts

Post by xnview » Thu Nov 20, 2008 2:37 pm

I have no problem if you enable alpha support
Pierre.

Micha
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Post by Micha » Thu Nov 20, 2008 3:04 pm

XnView is the only software I know, that allow to disable the alpha channel, so that the original background can be seen. That's a nice feature.

Here an example: the render output of Vray create an image and at XnView the user can choose - background or transparency. But after downscale the image show artefacts at XnView.

http://rapidshare.de/files/40953315/PNG_test.zip.html

Maybe Photoshop destroyed the original background info, but if I use the WINDOWS miniatur preview, than I get a clean white background without artefacts at the downscaled image and the black disk example looks perfect too.

It could be nice, if XnView could show the background without artefacts.

If I downscale an image per XnView, than anything is perfect, the background is keeped. So I suppose so, that Photoshop cause the problems. But maybe XnView can handle it like the WINDOWS preview.

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Post by XnTriq » Thu Nov 20, 2008 11:50 pm

Micha wrote:If I downscale an image per XnView, than anything is perfect, the background is keeped. So I suppose so, that Photoshop cause the problems.
Photoshop is the culprit :|

Micha
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Post by Micha » Fri Nov 21, 2008 7:17 am

Thank you for the interesting links.

So my question now: could it be possible that XnView read images created/edited by Photoshop and show the images like the WINDOWS preview it do? The problem is, I can't batch convert the images with transparency to images without transparency per XnView, if the images are edited per photoshop. I understand now, that my wish is a photoshop compatibility wish only. :wink:

An other little wish/issue at this place: if I select a thumbnail, than I get a big preview image and I can turn on/off the alpha per Ctrl-H. Works fine. But toggle the Mask per "M" dosn't work, because the thumnail selection jumps to the images starting with "m" in the name. Couldn't better to get Ctrl+M working for it?

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Re: Bug: PNG transparency showed with artefacts

Post by pic_viewer » Fri Nov 21, 2008 7:44 am

xnview wrote:I have no problem if you enable alpha support
Pierre has no problem when Micha enables alpha support????

The test pic is shown wiith a white square background on my system, no matter if alpha channel is disabled or enabled in XnView settiings.

Please someone explain this better, as I am interested in png transparency too.

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Clo
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No pb either

Post by Clo » Fri Nov 21, 2008 8:19 am

:arrow: pic_viewer

:) Hello !

• I've no problem either with the pic shown here, I get the black disc and the transparency alright,
the anti-aliasing is done by gradation of the transparency as it should…

- You might check the options >> Read/Write >> Read >> PNG and UNtick the two boxes "Compose…",
then tick "Use Alpha Channel" in the View Menu…
- I agree that is neither clear nor logical… but it works !

:mrgreen: VG
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Micha
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Post by Micha » Fri Nov 21, 2008 8:53 am

"Enable alpha support"? I would like to see the thumbnails and previews without alpha, with background - should I realy enable alpha and if yes where?

Here an example of my problem here. The alpha PNG read options are unchecked. I would like to see a black disk and the Dino image without black artefacts.

Image

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Clo
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Sigh--- and tricks

Post by Clo » Fri Nov 21, 2008 11:14 am

:arrow: Micha

:) Hi !

• The transparency in the thumbnails is possible when using a 32 BPP screen display only,
otherwise the BG is always black for all 32 BPP image-types (PNG, ICO etc.)

• With the right screen mode like shown below, you don't get the BG of the thumb nail itself (BG2),
but the one of the board ¦ thumb nail area (BG1) :

ImageImage

- So, if you set the BG1 as black, you'll get always a thumb nail with a black BG…

• In the Preview, no problem, since there is a single BG colour.

• You can also play with the chequered pattern colours, even set the two as the same value to get a plain coloured BG
(white or whatever) in View and Preview.

:mrgreen: KR
Claude
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Micha
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Post by Micha » Fri Nov 21, 2008 12:07 pm

I'm not sure I understand - I don't want transparency, I want to see the original background color of the image. I'm looking for, that XnView ignore the transparency, but without artefacts. In my example it should be a black disk on a white ground and not a black quadrat at a white ground. The quadrat is the problem, because original it's a disc. The quadrat is caused by artefacts at XnView only. All other image software show me a disk. My attached black disk image is shown right at the Operabrowser here, but at XnView it's a quadrat.

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Post by xnview » Fri Nov 21, 2008 12:08 pm

Could you post a screenshot? I've have a circle
Pierre.

Micha
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Post by Micha » Fri Nov 21, 2008 12:22 pm

I posted the screenshot two post above - the big one with the quadrat, the dinos and sankta claus.

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Post by xnview » Fri Nov 21, 2008 12:27 pm

Micha wrote:I posted the screenshot two post above - the big one with the quadrat, the dinos and sankta claus.
Oh sorry, could you send the png file?
Pierre.

Micha
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Post by Micha » Fri Nov 21, 2008 12:28 pm

It's posted at my first post above allways. :wink:

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Post by xnview » Fri Nov 21, 2008 12:35 pm

Micha wrote:It's posted at my first post above allways. :wink:
Houps :-) I have the thumbnail & preview for these 2 files. Do you have tried to recreate thumbnails? Alpha is enabled? No 'compose...' enabled in png settings?
Pierre.

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