Low quality wallpaper, really?

[j7n]

Windows NT6 keeps on giving. This one's kinda trivial. But considering the increased size of the system and focus on sleek visuals, I don't understand how they could have messed this up.

I have some wallpapers in bitmap format in a directory, prepared for a few screen resolutions. They are ready to be displayed, and work just fine in Windows XP. If I set the wallpaper using the Desktop Properties or the right-click menu on an image file, the data gets encoded to a poor quality JPEG file with color subsampling. It is 1 "actively used" file and should not be compressed.

%appdata%\Roaming\Microsoft\Windows\Themes\Application Data\TranscodedWallpaper.jpg

To set the wallpaper properly I need to enter the path to the image file into the registry.

HKCU\Control Panel\Desktop\Wallpaper

Then execute this command from the Run box to refresh it (a bat file does not work) {REF}:

rundll32.exe user32.dll, UpdatePerUserSystemParameters

Seriously?

[UCyborg]

Yup, it imports them as JPEG with 85% quality. I didn't find whether there was any reason for this. Windows 8 added ability to set background per-monitor and PNG format support and AFAIK this one doesn't get further compressed or converted to JPEG. Windows 10 added JPEGImportQuality setting in registry (must be manually created), so at least compression can be disabled this way.

One is better off with a 3rd party tool. I personally let Actual Window Manager manage desktop wallpapers, which also addresses lack of native ability to set background per-monitor.

[j7n]

Wow, Actual Window Manager still claims Windows 2000 compatibility. Not that I plan to use Windows 10 for many reasons, but I'm curious if you set JPEGImportQuality to 100, does color subsampling remain active (blurry red shapes)?

[vinifera]

i dont have this issue

i even compared with hashtab, the copied one matches original

pic in question is:

type: JPG
dimension: 4000x3000
size: 1.6 MB

or am i missing something here ?

Edited September 8, 2021 by vinifera

[UCyborg]

On 9/8/2021 at 12:30 AM, j7n said:

Not that I plan to use Windows 10 for many reasons, but I'm curious if you set JPEGImportQuality to 100, does color subsampling remain active (blurry red shapes)?

Unfortunately, yes.

10 hours ago, vinifera said:

or am i missing something here ?

I don't know, AFAIK it's an over decade old quirk (from MS point of view it's probably by design) and computers have only gotten more powerful since.

https://social.technet.microsoft.com/Forums/en-US/0c02f2cb-39cd-4f2d-bd4e-154fd2165b69/my-wallpaper-gets-badly-compressed?forum=w7itproui