Another possibility is that LCD panel dithering (controlled by the i915 kernel driver) has changed between kernel versions.
If your LCD panel is natively 6-bits per channel then the kernel should be turning on dithering for you, since the shell is typically rendered as 8-bits per channel. If dithering is not enabled then you will see banding and effectively see a loss of 75% of your colours and gradients. But the tricky part is for a developer to find a machine with the same problem. The problem will be specific to your GPU model (the dithering logic in i915 varies between generations), and specific to the LCD panel type in that laptop. Effectively we will need to find a similar Haswell laptop with a similar LCD type, which is the hard part... ** Summary changed: - Colour banding and artefacts appear system-wide on an Intel HD Graphics 4400 system + Colour banding and artefacts appear system-wide on an Asus Zenbook UX303 with Intel HD 4400 graphics -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1749420 Title: Colour banding and artefacts appear system-wide on an Asus Zenbook UX303 with Intel HD 4400 graphics Status in linux package in Ubuntu: Incomplete Bug description: - Ubuntu 18.04 (with updates as of 14 Feb 2018). - Laptop: Asus Zenbook UX303 - CPU: Intel i5 4210U - Graphics: Intel HD 4400 Problem description: Colour artefacts and banding in all apps. Graphics, photos and videos display as though the colour range is improperly configured. See this photo of a 1080p video taken with a camera (poor quality, but illustrates the issue): https://ubuntucommunity.s3-us- east-2.amazonaws.com/original/2X/c/c8f266715226953c6a77db6367ff9b7895784e35.jpg Look at the sky’s light colours. They display with smooth gradients on Ubuntu 16.04, but as the photo illustrates 18.04 seems to display the video with a smaller range of white colours. This is the most apparent with either very dark or very light colours. Even on window titlebars the banding is visible (displayed as lines with different shades of grey/black). Compared with a PrtSc shot of the same image: https://i.imgur.com/VkOSCaQ.png The artefacts are not present on PrtSc shots that are taken on Ubuntu 18.04 but viewed on a different system (16.04 and Windows). Installing a previous kernel version fixes the issue completely. I used UKUU Update Utility to install kernel 4.4 (the same that I use in Ubuntu 16.04 without issues) and upon a reboot with 4.4 running on 18.04 everything displayed smoothly. So this indicates that the system might be using a sub-optimal colour depth with the newer kernel? ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: linux-image-4.13.0-32-generic 4.13.0-32.35 [modified: boot/vmlinuz-4.13.0-32-generic] ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13 Uname: Linux 4.13.0-32-generic x86_64 ApportVersion: 2.20.8-0ubuntu10 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC0: ystein 1344 F.... pulseaudio /dev/snd/controlC1: ystein 1344 F.... pulseaudio CurrentDesktop: ubuntu:GNOME Date: Wed Feb 14 11:25:43 2018 EcryptfsInUse: Yes HibernationDevice: RESUME=UUID=d0bae648-a4d8-454c-b9fc-4cc04874d6c1 InstallationDate: Installed on 2018-02-12 (1 days ago) InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180210) Lsusb: Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 004: ID 8087:07dc Intel Corp. Bus 001 Device 003: ID 064e:9700 Suyin Corp. Asus Integrated Webcam Bus 001 Device 002: ID 046d:c52b Logitech, Inc. Unifying Receiver Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub MachineType: ASUSTeK COMPUTER INC. UX303LA ProcFB: 0 inteldrmfb ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-32-generic.efi.signed root=UUID=25279d7b-cc8a-4fee-9088-cfc69607cbca ro quiet splash vt.handoff=1 RelatedPackageVersions: linux-restricted-modules-4.13.0-32-generic N/A linux-backports-modules-4.13.0-32-generic N/A linux-firmware 1.170 SourcePackage: linux UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 09/01/2014 dmi.bios.vendor: American Megatrends Inc. dmi.bios.version: UX303LA.204 dmi.board.asset.tag: ATN12345678901234567 dmi.board.name: UX303LA dmi.board.vendor: ASUSTeK COMPUTER INC. dmi.board.version: 1.0 dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 10 dmi.chassis.vendor: ASUSTeK COMPUTER INC. dmi.chassis.version: 1.0 dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX303LA.204:bd09/01/2014:svnASUSTeKCOMPUTERINC.:pnUX303LA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX303LA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0: dmi.product.family: UX dmi.product.name: UX303LA dmi.product.version: 1.0 dmi.sys.vendor: ASUSTeK COMPUTER INC. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : email@example.com Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp