[IPP] More Discussion on bi-level, mono-chrome and color

[IPP] More Discussion on bi-level, mono-chrome and color

Michael Sweet msweet at apple.com
Mon Apr 18 20:37:52 UTC 2011

On Apr 18, 2011, at 11:38 AM, Petrie, Glen wrote:
> Can we change the required on mono to optional and bi-level be required.
> Bi-level           required for any printer
> Color               required is color printer
> Mono              1 toner – optional
> Mono              >2 toners – optional
> And the other is the table are optional
> Basically mono is a dithering of a single-color to produce an output from saturation to white.  But dithering is a fancy thresholding (bi-level);

I don't agree with this. Thresholding is not dithering, which by definition adds noise to the signal (in this case 2D color arrays) in order to more accurately portray the signal given limited output capabilities. The usage here is not to describe a particular algorithm but rather to specify intent: high contrast black and white output. You'd use this mode when scanning and printing forms, for example. (Oops - time for another thread...) It is pretty clear I need to convert Table 2 to a list of paragraphs describing the keywords and their meanings in detail.

The current requirements map to use cases - color and grayscale (monochrome) printing are required for our current use cases. "Bi-level" is not, although it is something we should consider for the scanned forms use case. We can continue to debate the requirements, but every OS and just about every driver for a color printer includes UI to print color as grayscale... If the intent is to allow a limited mobile client to do the same, we need to ask the printer to help out, and we can decide whether that means 1-color or process (N-color, N>1) black.

Michael Sweet, Senior Printing System Engineer, PWG Chair

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