Resize does not preserve the alpha channel of PNG images

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cermini
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Joined: Mon Feb 21, 2011 10:22 am

Resize does not preserve the alpha channel of PNG images

Post by cermini »

1. Resize does not preserve the alpha channel of 32bit PNG images (in a PNG-to-PNG conversion) and does not inform for the loss of it.
2. The status bar ignores the alpha channel of 32bit PNG images - it does not indicate in any way the existence of alpha channel in the selected image.
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xnview
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Re: Resize does not preserve the alpha channel of PNG images

Post by xnview »

cermini wrote:1. Resize does not preserve the alpha channel of 32bit PNG images (in a PNG-to-PNG conversion) and does not inform for the loss of it.
2. The status bar ignores the alpha channel of 32bit PNG images - it does not indicate in any way the existence of alpha channel in the selected image.
I can't reproduce, "Option/Read/PNG/Compose ...." is checked??
Pierre.
cermini
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Joined: Mon Feb 21, 2011 10:22 am

Re: Resize does not preserve the alpha channel of PNG images

Post by cermini »

Thanks for pointing this.

Tools -> Options -> General -> Read/Write -> Read -> PNG -> Compose image with alpha (32bits) was checked. By default this option is not checked in XnView v1.97.8. It appears that XnView used settings from previous installation.
If that's the case it is possible that it used a setting, which I made so long ago that I don't remember it at all.
MasterHD
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Joined: Wed Jun 22, 2011 4:34 am

Re: Resize does not preserve the alpha channel of PNG images

Post by MasterHD »

I'm having the same problem resizing PNG's. The alpha layer just turns black for any resample type other than "bilinear" or "nearest neighbor" (and those produce pixelated images that don't look good).
I tried enabling/disabling the "Option/Read/PNG/Compose ...." in every combination. I can't even perform a color depth "transformation" and retain the alpha layer. Am I doing something wrong? I've tried this with xnConvert as well with no luck.

Thanks for any help.
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xnview
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Re: Resize does not preserve the alpha channel of PNG images

Post by xnview »

Is it a 32bits PNG?
Pierre.
MasterHD
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Re: Resize does not preserve the alpha channel of PNG images

Post by MasterHD »

The color is 8-bit depth, and all 4 channels (RGBA) are active. But I have since moved on because I didn't realize there was a response here :(
Have you been able to reproduce this problem?
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xnview
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Re: Resize does not preserve the alpha channel of PNG images

Post by xnview »

MasterHD wrote:The color is 8-bit depth, and all 4 channels (RGBA) are active. But I have since moved on because I didn't realize there was a response here :(
Have you been able to reproduce this problem?
No, please send me a picture file?
Pierre.
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