Re: [Gimp-developer] 10-bit display color depth support (30-bit, deep color)

A fix in message

I am using EIZO Color Edge CG279X monitor and the quoted message was from Nov 2020.


On 12/5/21 12:43 PM, Magnus Larsson wrote:
Hello gimp-developer-list,

In this mail to gimp-user, from /From/: LKH about 10-bit display color depth support (30-bit, deep color) the discussion (from last year Nov 2021) end with:


 Re: [Gimp-user] 10-bit display color depth support (30-bit, deep color)


 * /From/: LKH <lkhgraf protonmail com>
 * /To/: Liam R E Quin <liam holoweb net>, "gimp-user-list gnome org"
   <gimp-user-list gnome org>
 * /Subject/: Re: [Gimp-user] 10-bit display color depth support
   (30-bit, deep color)
 * /Date/: Sun, 15 Nov 2020 06:19:32 +0000


I am still experiencing banding with a gradient made from scratch in GIMP 2.99 in 32-bit floating point mode on X11 when xdpyinfo and xwininfo say the window is 30-bit. If dithering is off the banding is obvious. I believe 16-bit support for TIFF is in GIMP anyway because it says it is in 16-bit mode after loading it.

I have tested Adobe Photoshop CC on both Windows and macOS and the monitor does successfully display in 30 bit. No amount of zooming in on the test gradient produces banding in those cases.


I am seeing the same thing as user LKH, that is GIMP does not render 30-bit, deep color on my Linux system. (I do not have Adobe Photoshop on Windows, so this I have not tested).

I understand many conditions have to be fulfilled:
1) Application can render: I am using GIMP_2_99_8-110-g44f6ee36fe compiled from git source.

2) OS can render: I am using Debian 11 with X11 with 30 bit depth enabled (not Wayland):
xwininfo -root | grep Depth =>   Depth: 30
glxinfo | grep "direct rendering" => direct rendering: Yes

3) I have an NVIDIA Quadro RTX 4000 GPU with NVIDIA drivers that support 30 bits and Nvidia Xserver Setting app report back 30 bits when checked

4) I am using EIZO GLX 2790X wide gamut monitor and monitor reports that it is operating in 10 bits when queried: EIZO monitor | Signal => Full Range, RGB 10 bit

5) A set of test files which actually has 10 bit or more raster and GIMP in 16 bit mode: GIMP | Image | Encoding => 16 bit

I can still see no difference between an 8 bit gradient (in 8 bits) and a 16-bit gradient (in 16 bits).

I use these test images (I have used other test files as well. Same result. No 10 bit gradation is rendered in GIMP display):
16_bit_TIFF: 8_bit_gradient:

What do you think?

I respect the complexity of 1-5 above, but feedback in gimp-user list refered to above, seem to indicate that GIMP can use 30-bit visuals, at least GIMP 2.99-x.

Best regards,

Magnus Larsson

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