1.6.5 - view - transparent index visible when zooming

[user0]

XnViewMP 1.6.5 64bit
Windows11 (23H2), display resolution 3840x2160, win scaling 150%

Viewer/Browser(Preview) - indexed palette
transparent index visible when zooming

To reproduce:
1. open test image in Viewer
- ☑ Use transparent index (<=8bits) [default state]

test_img_transparent_index.png (1.75 KiB) Viewed 1514 times

index 1 (green) is transparent


Issue A
2. press M to "Show alpha"
nothing happens at default 100% zoom
3. zoom to any value <>100%, eg 71%
transparent index became visible

A_show_alpha_on_paletted_img.png (290 Bytes) Viewed 1158 times

expected behavior
for indexed color images without alpha, "Show alpha" command should:

• either be disabled
  like in Preview pane (Browser) and other Show RGB channel commands

• or work at any zoom level
  as functionality to show transparent index(es) is handy, only naming does not match, but not a big deal

Issue B
2. uncheck 'Use transparent index (<=8bits)', eg via Ctrl+Alt+H
index 1 (green) is visible
3. zoom to any value <>100%
index 1 (green) became transparent
same issue in Preview pane (Browser)



Suggestion

• rename
  Use transparent index (<=8bits) →
  Use transparent index (≤ 8-bit)
  ≤ U+2264
  8-bit color
  8 bits per pixel

Related

• issues
  - fixed -
  1.8.0 - viewer - change color depth - 32bit result when converting 8 to 24 (1.8.1)
  1.6.5 - view - transparent index visible when zooming (1.8.1) current post
  1.7.2 - viewer - Show alpha became disabled (1.8.0)
  1.4.0 - viewer / batch convert - Change color depth to 8bit + Filter = mess (feature)

• suggestions
  App UI - menu structure - View - improve channel commands

[xnview]

Issue A: I can't reproduce

Issue B:
Thanks to your detailed description I can reproduce the problem.

[user0]

Issue A: I can't reproduce

1. close app
2. open paletted image (8bit, no alpha) via double click in win file explorer
'Show alpha (M)' menu command is enabled
3. change zoom to any value <>100%
4. press M
issue appears
Show alpha (M) is disabled - as it should be for paletted image

[xnview]

Strange, 'show alpha' is disabled

[xnview]

This problem is supposed to be fixed in XnView MP 1.8.1. Please check and confirm the bug fix here.

[user0]

fixed in 181