[MFD] Question on Resolution Versus Qaulity

[MFD] Question on Resolution Versus Qaulity

[MFD] Question on Resolution Versus Qaulity

Petrie, Glen glen.petrie at eitc.epson.com
Thu Feb 2 16:55:33 UTC 2012


Ira

 

Does a conforming Print Service accepting a PWG:PJT  have to behave
accordingly!!!???? (It is not an IPP printer!)

 

glen

 

________________________________

From: Ira McDonald [mailto:blueroofmusic at gmail.com] 
Sent: Thursday, February 02, 2012 8:54 AM
To: Petrie, Glen; Ira McDonald
Cc: Michael Sweet; mfd at pwg.org
Subject: Re: [MFD] Question on Resolution Versus Qaulity

 

Hi Glen,

I see the logic of your comments.

But IPP/2.0 Second Edition *did* specifically resolve this
"quality" versus "resolution" question based on quite a lot
of mailing list and face-to-face discussion.  This is stated
in on page 21, section 6.2, item 8 of PWG 5100.12.

So a conforming IPP Printer has to behave accordingly.

We can add more discussion in IPP JPS3, if that seems
appropriate, but we really can't reverse the IPP/2.0 SE, 
because that would not be backward compatible.

Cheers,
- Ira

Ira McDonald (Musician / Software Architect)
Chair - Linux Foundation Open Printing WG
Secretary - IEEE-ISTO Printer Working Group
Co-Chair - IEEE-ISTO PWG IPP WG
Co-Chair - TCG Trusted Mobility Solutions WG
Chair - TCG Embedded Systems Hardcopy SG
IETF Designated Expert - IPP & Printer MIB
Blue Roof Music/High North Inc
http://sites.google.com/site/blueroofmusic
<http://sites.google.com/site/blueroofmusic> 
http://sites.google.com/site/highnorthinc
<http://sites.google.com/site/highnorthinc> 
mailto:blueroofmusic at gmail.com
Winter  579 Park Place  Saline, MI  48176  734-944-0094
Summer  PO Box 221  Grand Marais, MI 49839  906-494-2434





On Thu, Feb 2, 2012 at 10:06 AM, Petrie, Glen
<glen.petrie at eitc.epson.com> wrote:

Mike,

 

Interesting but I still believe my conclusions support both a simple and
sophisticated user-centric model.  A simple user-centric model will
always use the "quality" setting and, for added "control", will set
"content type" to get the desired output.   Sophisticated users will
want to control the finer details and, thus, may want a specific
resolution.   

 

As to "draft" operations or any other quality setting operations:  in
general, no print vendor is going to use simpler/faster dithers or
color-transform or not perform print row interleaving, if it reduces the
overall printed quality of the output simply because the user set
quality setting to draft/normal/high in a Print Client.   There would be
insignificant amount of processing required; no need to support multiple
dither/color transforms routines; and an unnoticeable amount of
additional (if any) overall print time.   If a user specifies a
resolution versus quality; then, saving ink was not his/her intent;
he/she wants a specific resolution for his/her specific reason.  While
bi-directional versus uni-directional printing are affected by quality
settings; print service internal selection (not user set) would also use
content-type (for example; high-quality text (bi) versus high-quality
photo(uni)) which, of course, bi versus uni, can also be done as a
function of resolution and the content-type.

 

The constraint is solved by;

 

1.	The content-type MUST be set;  

	a.	The default could be "text and graphic"

2.	If user sets resolution; then the Print Services uses this
resolution along with content-type.  The Print Service will ignore any
quality-setting and set any internal processing based on resolution and
content-type only.  

	a.	If the resolution set is not supported; then return an
error.  (How this could occur from a print client that received printer
capability data is unknown but just in-case the user is allowed to
"type" in any resolution they want!) 

3.	If user set quality but not resolution, then

	a.	The Print Service uses content-type and quality-setting
to determine a resolution and internal processing.

 

IMHO, the user must always be in control.  Setting resolution is more
specific than setting quality, since quality is qualitative versus
quantitative; thus, if a user sets a resolution; then that what should
be done. 

 

I think we will have to agree to disagree and simply move on!

 

glen

 

 

________________________________

From: Michael Sweet [mailto:msweet at apple.com] 
Sent: Wednesday, February 01, 2012 5:00 PM


To: Petrie, Glen
Cc: mfd at pwg.org
Subject: Re: [MFD] Question on Resolution Versus Qaulity

 

Glen,

 

On Feb 1, 2012, at 3:45 PM, Petrie, Glen wrote:

	

	Conceptually there is no reason a printer could not support a
draft mode for multiple resolutions (and this is in fact the case in
CUPS/Mac OS X), so preventing both from being specified will do a
disservice to the user and printer/driver.

	 

	[gwp] So if we have "draft" at 75, 150, 300; and the user can
select both "draft" and 300; then what is the value of "draft" to the
Print Service since the Print Service was told to print at 300 dpi.

 

"Draft" might select (for example) bidirectional printing on an inkjet
with no interleaving of dot rows. It could also use a simpler/faster
dithering algorithm,  simpler/faster color transform, use less inks
(i.e. just CMYK instead of CMYKcmk), etc.

 

	

	[gwp] Users are more likely to select "quality" equals "draft"
and "contentOptimize" equals "photo" and not a dpi (ops: resolution).
If a user 'really understands' the Print Service performance for
differing dpi's (again ops: resolution's); then "quality" should never
win because the user knows exactly what dpi they want!

 

Users do not know how quality and resolution interact, and in the
absence of the JPS3 mechanisms for doing constraint resolution there is
no way for the client to know either.

 

	

	Quality != Resolution.  They may be related, and there may in
fact be constraints that cause a particular combination to conflict, but
they are not mutually exclusive and express separate intent.  The
IPP/2.0 recommendation to prefer Quality over Resolution when there is a
conflict is a pragmatic approach to automatic conflict resolution.

	 

	[gwp] Print-Resolution is a function of both Quality AND
Content-Optimize.   Any printer today can determine a resolution from
these two values.  If a user specifies a resolution then the Print
Service should use the resolution (resolution is always the winner)
since the user is stating they want the specified resolution that gives
them a desired quality for the content!

 

and if that resolution is supported by the printer then by all means it
should use it! But if not, the printer should let the client know it
can't use that resolution and  use the closest resolution instead...

 

[gwp] The conclusion is then

 

1.	Specified Resolution wins over "Quality"  - always, since the
User specified 'use this resolution".

 

The user specified "use this quality". One has to win, and IMHO (and
based on what we agreed to and approved in IPP/2.0 SE) Quality wins over
Resolution.

 

	

	1.	 
	2.	Content-Optimize MUST be required - for a printer to
properly determine the correct resolution when resolution is not
specified.

 

That's what defaults are for...

 

2.	 
3.	Print-Quality  is [Quality (-Intent) + Content-Optimize ] or [
Resolution] but not both.

 

Again, these elements are related but not mutually exclusive.

 

_________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair

 


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