TGA puzzle

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terrypin
Posts: 470
Joined: Tue Jun 29, 2010 9:51 am
operating_system: Windows 10
System_Drive: C
32bit or 64bit: 64 Bit
motherboard: Asus Z170 Pro 4
processor: Intel Core i7 6700K 4.0GHz
ram: 32 GB
Video Card: None - uses built-in graphics
sound_card: HD onboard sound card
Hard_Drive_Capacity: 4.256 TB
Monitor/Display Make & Model: iLyama Prolite E2403WS 24" 1920x1200
Corel programs: Paint Shop Pro 8; Paint Shop Pro 2018
Location: East Grinstead UK

TGA puzzle

Post by terrypin »

Can someone help me get my head around the way that various programs open TGA files please.

Starting simply, why does my test file open differently in PSP 8 versu 2018?

Image

Image
--
Terry, East Grinstead, UK
Using PSP 8 & PSP 2018 under Win 10
LeviFiction
Advisor
Posts: 5959
Joined: Thu Oct 02, 2008 1:07 pm
operating_system: Windows 10
System_Drive: C
32bit or 64bit: 64 Bit
motherboard: Alienware M17xR4
processor: Intel Core i7-3630QM CPU - 2_40GH
ram: 6 GB
Video Card: NVIDIA GeForce GTX 660M
sound_card: Sound Blaster Recon3Di
Hard_Drive_Capacity: 500GB
Corel programs: PSP: 8, 9, X, XI, X2, X8,X9, 2018, 2019
Location: USA

Re: TGA puzzle

Post by LeviFiction »

So, TGA files are able to contain a single alpha channel. The image has to be saved 24/32 bit format uncompressed for this channel to be maintained.

Well, with some very limited testing it looks like PSP8 does not load this channel in my default you either have to load a selection or mask from alpha channel to see the result that you see in 2018. In PSP2018 it seems to load in the alpha channel as part of the image deleting anything that isn't inside the area indicated by the alpha channel. I'm unsure which version this started with. PSP8 - PSPPX2 all work the same opening the full image without applying the alpha channel.

A similar problem exists with TIFF files that have an alpha channel. PSP merges the alpha channel with the image.
terrypin
Posts: 470
Joined: Tue Jun 29, 2010 9:51 am
operating_system: Windows 10
System_Drive: C
32bit or 64bit: 64 Bit
motherboard: Asus Z170 Pro 4
processor: Intel Core i7 6700K 4.0GHz
ram: 32 GB
Video Card: None - uses built-in graphics
sound_card: HD onboard sound card
Hard_Drive_Capacity: 4.256 TB
Monitor/Display Make & Model: iLyama Prolite E2403WS 24" 1920x1200
Corel programs: Paint Shop Pro 8; Paint Shop Pro 2018
Location: East Grinstead UK

Re: TGA puzzle

Post by terrypin »

Thanks Levi, appreciate that fast and characteristically helpful reply.

I'm pursuing a likely bug in my video editor, Magix Movie Edit Pro Premium (MEPP), which uses that file to display a caption. But googling about TGA and opening that specific file in both my PSP versions in the hope of insight has only confused me further!

If anyone is curious, the nature of the strange behaviour I'm seeing in MEPP is that the caption effect is disappearing from some (and later all) of the multiple captions in which it was used. The sort of behaviour I might expect if the TGA's alpha channel was somehow getting switched off when the file was used a few times! I wonder if there's any parallel in PSP that might indicate that the file is 'unstable'?

Should anyone want to play with it and let me have any feedback, I've uploaded it here:
https://www.dropbox.com/s/2xbyj4qlww16f ... .tga?raw=1
--
Terry, East Grinstead, UK
Using PSP 8 & PSP 2018 under Win 10
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