Disable wallpaper gamma?

[thany]

By default, Mint Cinnamon 18.1 appears to apply some kind of gamma to any desktop wallpaper I set, including the default ones, making them look rather freaking ugly, tbh.

When I set a wallpaper, it looks fine. But then, after a reboot, it has applied some kind of gamma (not to be confused with brightness, it looks much more like gamma). I can't find a setting for this anywhere. I'm running it inside a Virtualbox VM (5.1.14). The virtual monitor is listed as uncalibrated and for some reason can't be calibrated either (the calibrate button is greyed out). But I don't think that's the problem. You see, *ONLY* the wallpaper is gamma'd, *everything else* is completely fine.

So TLDR: how to disable the default wallpaper gamma?

[nanners]

This sounds like a VM issue more than anything, but right now there's no easy way to adjust gamma-only in Mint that I'm aware of. Brightness can be adjusted in /proc/acpi/video/VGA/LCD/brightness, but it sounds like you aren't worried about that. VMs and their settings vary literally from machine to machine, down to the drivers being used in the host to the preferences to the v-drivers inside VirtualBox to the system settings in the guest. How all that stuff gets translated from host to guest and back is full of places that can change a setting like gamma, depending on the method of virtualization in use. The setting being greyed out is probably because you are missing the guest additions disc (iso) in your VM. Getting and installing that is your best bet to get those settings activated. If you already have it and it's greyed out, that would be a good question for the guys at Oracle or guys from whichever OS you are using VirtualBox in. Also make sure your monitor isn't using any correction or auto-adjustment itself, independent of the PC. It's a common feature on most monitors now and might be why only parts of a screen are getting enhanced seemingly dynamically.

From there I'd need a bit more info about your system and the drivers being used. Specifically the output of "inxi -G" inside of Mint and also one from the host operating system (which is honestly just as likely a factor as the guest with the color settings). If you are using a Mac or Windows I have limited experience with VMs there, but if I can help I'll try

[thany]

I'm pretty much convinced it's nothing to do with drivers, nor a VM issue. That's because it is literally only the wallpaper that is gamma'd. Everything else is totally fine.

That's why I thought there'd be some setting to adjust colour for wallpapers only, or something. That's also why I wouldn't assume it to be a VM issue. I wouldn't think the driver would handle a desktop wallpaper image differently from any other pixels...

But no matter, I can still give you some more details about the host. It's a Windows 10 box with GF GTX970, Intel 6700K and all the latest drivers and updates, at the time I write this.
As for "inxi -G", here you go:

Code: Select all

Graphics:  Card: InnoTek Systemberatung VirtualBox Graphics Adapter
           Display Server: X.Org 1.18.4 drivers: vboxvideo (unloaded: fbdev,vesa) Resolution: 1240x899@59.96hz
           GLX Renderer: Chromium GLX Version: 2.1 Chromium 1.9

Hopefully it helps

/edit
Here's some screenshots:

Good boy, after changing it:


With gamma, after a reboot:


You can see here, *only* the wallpaper is gamma'd, the rest of the screen is totally normal. This is why I wouldn't suspect any drivers, nor the virtual hardware, nor the host machine.

[nanners]

With those screenshots it definitely emphasizes what you meant.. that is bizarre. When you say you "fixed" the gamma on the upper image, what did that entail? Have you tried wallpapers of various colors, color depth, etc? I know grey wallpapers tend to look ugly on Mint around the borders because of the default settings. Also, have you tried xbacklight? I skimmed out previous posts and didn't see this mentioned yet, but if it's in there, my apologies. You'd need to get it from the repo, it's command-line only, but super simple. The regular xbacklight --help has about five settings you can modify and really helps with my Samsung LCD and fixing the ugly-grey problem Mint has around the desktop. Also, have you tried a color profile? Your monitor will have a default .icc that Mint is (probably) using, but there are a bunch of additional profiles available with the gnome-color-manager, including professionally calibrated stuff down to the standard international HDMI profile for end users straight from Adobe. Maybe worth a shot. Don't forget to restart between changes as well.

Beyond all that, you know what it reminds me of is a third-party color-correction filter being applied somewhere. Back in Windows I used to use an ATI tray tool that would apply bright/gamma/saturate settings in addition to their own "Color Enhancement/Correction" setting. It would basically do a pseudo-dynamic contrast over your display to get the most out of colors and it could look god awful on super bright images. But let me mess around in a VM and see if I can mimic that screenshot.

Edit: Oh and try xcalib as well. I personally have never used it, BUT I see it mentioned frequently as the fix for lots of color issues in ubuntu/mint. It's a monitor calibration tool.

Edit 2: Also, as long as it's in the VM and you can't really hurt much, try every available resolution and refresh rate and DPI setting you can in Mint to see if that is causing it.

[JosephM]

This is an issue that only occurs in some cases in Virtualbox. If Cinnamon is fully up-to-date install dconf-editor and navigate to org.cinnamon.muffin and change the value of background-transition from "blend" to "none" or "fade-in".

[thany]

Sorry I can't find a `background-transition` value in dconf-editor. Not at the node you mention, nor anywhere else.

[JosephM]

You can check your muffin version by running

Code: Select all

muffin --version

in a terminal. It should 3.2.2. If not make sure you are fully updated.

[thany]

Ok, this is weird. The problem seems to have magically disappeared. Either by an update in Mint, or by an update of Virtualbox...