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Posted to user@guacamole.apache.org by Vieri <re...@yahoo.com.INVALID> on 2020/09/28 08:44:19 UTC
color-depth and DPI
Hi,
I'd like to make sure that specific RDP connections get the best image quality regardless of bandwidth.
The manual says that color-depth can be set up to 24. Does setting it to 32 make any difference?
Should I leave DPI undefined, or should I manually give it a value of, say, 300?
Regads,
Vieri
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Re: color-depth and DPI
Posted by ivanmarcus <iv...@yahoo.com.INVALID>.
FWIW I agree with Nick.
I've never [had to] set the DPI, but have generally set colour-depth to
32-bit for most users, along with font-smoothing, because it gives the
best visual experience for little penalty on fast connections. It may be
that 32 is the default and doesn't need specifically setting (Nick?) but
I'd tended to specify these things right from day one.
Occasionally I've set individual connections down to 256 colour, or
16-bit, to resolve certain issues - mostly attempting to speed up Autocad.
Also I found certain versions of FreeRDP required setting to a lower
colour display, otherwise you'd get 'weird' results. However the need to
do this seems to have dissipated recently.
On 29/09/2020 5:08 a.m., Nick Couchman wrote:
> On Mon, Sep 28, 2020 at 4:44 AM Vieri <re...@yahoo.com.invalid> wrote:
>
> Hi,
>
> I'd like to make sure that specific RDP connections get the best
> image quality regardless of bandwidth.
>
> The manual says that color-depth can be set up to 24. Does setting
> it to 32 make any difference?
>
> Should I leave DPI undefined, or should I manually give it a value
> of, say, 300?
>
>
> Unless you're seeing specific issues with the connections, I'd just
> leave it alone.
>
> -Nick
Re: color-depth and DPI
Posted by Nick Couchman <vn...@apache.org>.
On Mon, Sep 28, 2020 at 4:44 AM Vieri <re...@yahoo.com.invalid> wrote:
> Hi,
>
> I'd like to make sure that specific RDP connections get the best image
> quality regardless of bandwidth.
>
> The manual says that color-depth can be set up to 24. Does setting it to
> 32 make any difference?
>
> Should I leave DPI undefined, or should I manually give it a value of,
> say, 300?
>
>
Unless you're seeing specific issues with the connections, I'd just leave
it alone.
-Nick
Re: color-depth and DPI
Posted by Vieri <re...@yahoo.com.INVALID>.
Thank you for the feedback.
Regarding the color-depth option I ask because the manual in chapter 5 (https://guacamole.apache.org/doc/gug/configuring-guacamole.html#rdp) says that "If specified, this must be either 8, 16, or 24.".
I too use 32 for some connections, and I'm guessing it's honored because:
PS C:\Users\vieri> Add-Type -AssemblyName System.Windows.Forms
PS C:\Users\vieri> [System.Windows.Forms.Screen]::AllScreens
BitsPerPixel : 32
I was wondering if there was a limitation of some sort, but I guess not.
Thanks
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Re: color-depth and DPI
Posted by Mike Jumper <mi...@glyptodon.com>.
On Mon, Sep 28, 2020 at 1:44 AM Vieri <re...@yahoo.com.invalid> wrote:
> Hi,
>
> I'd like to make sure that specific RDP connections get the best image
> quality regardless of bandwidth.
> ...
> Should I leave DPI undefined, or should I manually give it a value of,
> say, 300?
>
Short answer:
No. The "dpi" parameter affects only how the client width/height are
interpreted, not image quality.
Long answer:
The "dpi" parameter controls the *effective resolution* of the display
only. It will not have any effect on the true remote display resolution as
it pertains to things like font/vector rendering quality, which Guacamole
(and typically Windows) assume is 96 DPI.
So why is the DPI used at all if it has no effect on the true DPI of the
Windows' display?
Very high DPI devices like modern cell phones have a great many pixels
covering a small area. If the true dimensions of these displays were sent
as-is to Windows, the screen that you see on the client side would be
unusable. With the Windows side assuming 96 DPI, you would end up with text
that would be readable on a large monitor but is just microprint on a
handheld device. To combat this, Guacamole's RDP support uses heuristics to
determine a width and height to request for the remote desktop that will be
"reasonable" based on the client-side DPI and dimensions.
Blindly using an effective 96 DPI would produce a display that typically
does not have enough screen real estate to be usable on small devices,
whereas blindly using the true client-side DPI would produce a display
that's unusable for the reasons noted above. Guacamole's heuristics will
typically select a DPI somewhere in between.
You can see the internals of how this is done here:
https://github.com/apache/guacamole-server/blob/ceabd68e280c416e31cc35b105eac33dc13eb11e/src/protocols/rdp/client.h#L46-L63
https://github.com/apache/guacamole-server/blob/ceabd68e280c416e31cc35b105eac33dc13eb11e/src/protocols/rdp/resolution.c
Specifying the "dpi" parameter overrides these heuristics.
- Mike