Preview Alpha Channel in XnView Classic is broken

[esenthel]

Latest release broke previewing images with alpha channels.
Press M to see alpha channel (show mask menu) doesn't always work, sometimes you need to press Ctrl+H first (Use Alpha Channel)

[xnview]

could you send me a picture file where it doesn't work?

[esenthel]

In latest version 2.49.4

Please use any image that has alpha channel, BMP, PNG, TGA, any
Then set zoom to be less than 100%, for example 50%,
Then press M key to show alpha, it won't work

Zoom in at 100%, alpha starts to work

In options I have "High Quality Zoom \ Reduce = ON"

[xnview]

it works here

[esenthel]

It's broken 100%
https://youtu.be/H5jyZxcHdUI

[xnview]

It's broken 100%
https://youtu.be/H5jyZxcHdUI

I can't reproduce, could you send me the file used, and which settings do you have in options>View?

[esenthel]

The problem happens with any/all images that have alpha channel.

[xnview]

it's crazy, it works correctly here

[esenthel]

Could it be related to Windows?
I have the latest version: Win 10 Home, ver 2004, os build 19041.508

But I've tested an older version, 2.37 just now, and it doesn't suffer from the same problem.
So I think something got broken in your code.
It was working fine just couple releases ago.

Is there a way to download older versions of your software? (v 2.48, 2.47 or something)
I could tell you between each release where the problem occurred, and you could check your code base for changes in that time frame, to see which change broke this function.

[xnview]

Could it be related to Windows?
I have the latest version: Win 10 Home, ver 2004, os build 19041.508

no it's XnView

Is there a way to download older versions of your software? (v 2.48, 2.47 or something)

http://download.xnview.com/old_versions

[XnTriq]

I'm not able to reproduce this issue with XnView Classic v2.49.4 and 966_1578623403.png or any other 32-bit PNG. However, we had a similar report a couple of years ago.

Related: Recommended settings

[esenthel]

I've tested a bunch of versions:
2.39 works great, no issue
2.40 has different problem, black background and white pixels on the border

2.40.png

2.41+ has problems with alpha sometimes visible, sometimes RGB, depending on zoom < or > 100%
Something got broken between 2.39 and 2.40

Attaching the entire XnView.ini file with settings, maybe you can do tests with it.

My Windows DPI Settings in 125%

[XnTriq]

Hello esenthel

I ran XnView v2.49.4 with the INI you provided (Windows DPI = 120%) and opened flour-flower-png-transparent-png-images-pluspng-2.png in fullscreen, edit and preview. Although I watched your screen recording again and made sure to follow the steps outlined in one of your previous posts…

In latest version 2.49.4

Please use any image that has alpha channel, BMP, PNG, TGA, any
Then set zoom to be less than 100%, for example 50%,
Then press M key to show alpha, it won't work

Zoom in at 100%, alpha starts to work

In options I have "High Quality Zoom \ Reduce = ON"

… everything works as expected

Related: Transparent pixels dont get filtered correctly