0004622: Optimized PNGs with palette have weird alpha

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Project

Category

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Date Submitted

Last Update

0004622

Zandronum

[All Projects] Bug

public

2026-07-22 12:24

2026-08-11 18:17

Reporter

IlyStr

Assigned To

Priority

normal

Severity

minor

Reproducibility

always

Status

new

Resolution

open

Platform

ASRock B550, AMD Ryzen 5 56 x64

Windows 10 LTSC Enterprise

OS Version

21H2 (19044.357)

Product Version

4.0-beta

Target Version

Fixed in Version

Summary

0004622: Optimized PNGs with palette have weird alpha

Description

Optimized 8-bit indexed PNGs with a lot of transparent pixels (like clouds, smoke, vapor and etc) have stepped and weird alpha in zandronum

Steps To Reproduce

1: optimize PNG using PNGOut, PNGCrush, DeflOpt
2: run in zandronum

Additional Information

Zandronum\GZDoom sprite comparison: https://imgur.com/a/WxTiadZ

Attached Files

Alpha_Bug__TestFog.pk3 (28,403 bytes) 2026-08-11 18:15
Alpha_Bug__TestFog-2.pk3 (28,403 bytes) 2026-08-11 18:15

Relationships

Relationships

Notes
~0024770 Fused (reporter) 2026-08-03 10:38	Could you provide a minimal example WAD that shows the behavior?

~0024773 IlyStr (reporter) 2026-08-11 18:15	Just spawn TestFog0 somewhere on the map

~0024774 IlyStr (reporter) 2026-08-11 18:15	Just spawn TestFog0 somewhere on the map

~0024775 IlyStr (reporter) 2026-08-11 18:17	(TestFog0 in the Alpha_Bug__TestFog.pk3, see attached files)

Notes

Date Modified	Username	Field
Issue History
2026-07-22 12:24	IlyStr	New Issue
2026-08-03 10:38	Fused	Note Added: 0024770
2026-08-11 18:15	IlyStr	File Added: Alpha_Bug__TestFog.pk3
2026-08-11 18:15	IlyStr	Note Added: 0024773
2026-08-11 18:15	IlyStr	File Added: Alpha_Bug__TestFog-2.pk3
2026-08-11 18:15	IlyStr	Note Added: 0024774
2026-08-11 18:17	IlyStr	Note Added: 0024775

Issue History