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
>> 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.
>> 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...
>> 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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