Image adjust adds greenish tint

Adjustments and Effects -> Essential -> Image adjust adds a greenish tint, even with default settings.

Problem is apparent on various movie files and even on a white .png that I used for testing.

This problem has been apparent for the last "few" versions of VLC. I haven't reported it till now as I assumed it was so obvious that someone would notice and fix it ;)

Steps to reproduce:

• Remove/rename vlcrc to ensure default settings,
• Launch VLC,
• Drag'n'drop a white .png file onto the main window, (I'll try to attach mine)
• Press pause before it finishes,
• Open Adjustments and Effects -> Essential and click the Image adjust checkbox

Tested on: 3.0.6 win64 3.0.7 win64 v20190416 (nightly)

System: Windows 10 Pro x64 version 1803, nVidia GTX 1080 Ti video card.

White.png

Added attachment:

• White.png

Added attachment:

• vlc_log.txt

(Just noticed my "tested on" lines are concatenated, but I can't seem to edit the ticket.)

Added attachment:

• Player_White.png

Added attachment:

• Player_Greenish.png

I've attached a couple of screen-shots to help demonstrate the bug. Both have been pasted into GIMP2 and the eyedropper tool used to show the colour values.

• Player_White.png shows 255,255,255 (RGB) working as expected (Image adjust OFF):

• Player_Greenish.png shows 253,255,252 which is the bug in action (Image adjust ON):

Can't reproduce on GNU/Linux. Ok for me I'm getting 0XFDFFFC (so same values, 253, 255, 252) using the adjust filter's defaults.

added Component::Video: filters Platform::Windows desktop labels

This has actually bugged me for a number of years, across multiple devices all running variations of Linux. It is most definitely not new. Nor is it limited to Windows like you have stated! Luckily the eye is an amazing device with an extremely good automatic white balance so things remain watchable and you stop noticing fairly quickly unless you a/b compare but it's still not very good.

I actually came across this looking to see if maybe there was a colour correction plugin written for VLC to fix this locally. My guess is it due to not correctly taking into account the colour weighting factor of the different colours when applying the effect. In fact the controls don't work as is standard in the industry at all, but at least some improvement can be made even with their current behaviour....

Points all my systems had in common.\ Intel integrated graphics using the i915 driver.\ Linux using X Windows\ X11 (XCB) video output module (none of the others displays correctly on all videos, not even Automatic.)

Comparison bitmap image

Added attachment:

• VLC 01.7z

I did some more testing, and the problem is not apparent in version 2.2.8-win64

2.2.8 didn't want to display White.png, so I made a test avi in VirtualDub.

I've attached a comparison image between version 2.2.8 and 3.0.7.1 as VLC 01.7z and the test avi as testpattern_u.7z

With the new test file I also noticed some "noise" in the 3.0.7.1 + ImageAdjust image.

Test avi

Added attachment:

• testpattern_u.7z

I have a fix for the greenish tint issue here: https://mailman.videolan.org/pipermail/vlc-devel/2019-July/126210.html

It's simply rounding values when dividing, instead of flooring the values. With this change, White.png shows up correcty as (255,255,255) when using the adjust filter's defaults.

I believe that the lines reported by Nighty (and shown in their screenshot) are a separate issue.

If someone makes a win64 binary with Tristan's fix, I'm happy to test it.

Replying to [comment:9 Nighty]:

If someone makes a win64 binary with Tristan's fix, I'm happy to test it.

You can try with the nightlies: https://nightlies.videolan.org/build/win64/vlc-4.0.0-20190723-0832/

Can confirm no problem with white.png in vlc-4.0.0-20190723-0832-dev-win64, but testpattern_u.avi still has a green tint. The whitest pixels are 251,253,250.

assigned to @tmatth

changed milestone to %4.0

added Version::master git label

See 11650366