On 2020-08-04 02:35, George N. White III wrote:
On Mon, 3 Aug 2020 at 11:53, Eyal Lebedinsky <fedora@xxxxxxxxxxxxxx <mailto:fedora@xxxxxxxxxxxxxx>> wrote:
On 2020-08-03 23:03, Tim via users wrote:
> On Mon, 2020-08-03 at 21:58 +1000, Eyal Lebedinsky wrote:
>> I recently started using a 4k TV as a monitor. The video is natively
>> 4k from the on-board Intel i7.
TV's rarely make good monitors. There are very different design tradeoffs.
Monitors are generally designed for close-up viewing and uniformity over a
wide range of viewing angles. TV's are viewed from a greater distance and
narrower range of viewing angles.
Displays good for both purposes are produced in low volumes and can
be very expensive.
>>
>> I noticed that I often get difficult to read text. This is even worse
>> when I use reverse video (black bg).
>>
>> Looking closer I can see that the image changes as I shift the window
>> one pixel sideways. Seems that
>> I get a different image when the left margin is odd and when it is
>> even.
>
> You may want to play with aliasing controls for font rendering.
I need to look into this (fonts) but hoped the problem is elsewhere.
The aliasing controls are important to make appropriate subixel choices,
not sure why you think fonts could be an issue. There are some issues
related to accurate placement of glyphs versus improved rendering.
> Perhaps your monitor doesn't have the traditional RGB (red green blue)
> pixel grouping? It might be in BGR sequence (your photo looks like that from the defocused blurs on the green text).
I still do not see why placing an windows at an odd x is different from an even position.
Moving the image changes between these two displays with each pixel shift.
Anti-aliasing uses subpixels, and moving one pixel reverses the colors between left and right
subpixels: [RGB][RGB][RGB] versus [BGR][BGR][BGR] so you can have [..B[RG.][...] or
[..R][BG.][...] for a sub-pixel shift to the left. If you want white, this works. But [..B][.G.][...]
on an RGB display will not look the same as [..R][.G.][...] is you use RGB settings on a BGR
display.
BTW this is what the pixels look like:
http://members.iinet.net.au/~eyaleb/attachments/20200801/dsc08774-part1.jpg
Looks like BGR left-to-right? Should that matter?
Yes.
I followed suggestions I found when searching. Some may be irrelevant to my setup. None made a difference.
- Applications - Settings - Appearance - Fonts
Sub-pixel order: BGR
- $ gsettings set org.gnome.settings-daemon.plugins.xsettings rgba-order 'bgr'
- $ sudo ln -s /usr/share/fontconfig/conf.avail/10-sub-pixel-bgr.conf /etc/fonts/conf.d/
I logged out/in and killed X to ensure things refreshed. No change.
Funny thing, trying gedit (rather than xterm) for testing, the text is rendered dark blue in one position
or dark red when the window is shifted one pixel. However, changing the DPI from the default(96) to 98 makes
the effect almost unnoticeable. It has no effect on xterm or thunderbird.
In fact, dragging this email I can see the text colour flickering between the two effects as I drag it sideways.
Still, using 'xmag' shows a nice text without any artifacts, so I wonder if this is an issue
with the actual monitor (TV) - assuming xmag grabs pixels from the screen not knowing how
they were painted (e.g. a font renderer).
Screen capture is usually done from a buffer at the level of pixel colors and ignores details
of screen painting.
As someone who is near-sighted, I can warn you that eye-glasses tend to separate colors
(high quality telescope optics have multiple layers with different materials to get around this).
I can see this by tilting my head up and down or side-to-side.
I may need to find a TV/monitor loaner to have a second reference point.
--
George N. White III
--
--
Eyal Lebedinsky (fedora@xxxxxxxxxxxxxx)
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