Now that we have raster graphic and color structures, we can discuss a number of models.
Let's think about a printer which is kind of PCL like.
1. A clean bitonal black/white monochrome printer.
that's a clear case.
One ColorMode record with Predefined_ID=monochrome, which means the PlaneImplementation attribute will be ignored (set it to PerPixel anyhow). No Plane element will be defined. I would define the ColorHandling feature hidden (Appearance).
2. A RGB color device.
You may define the same ColorMode record as in #1.
Additionally you likely have a color record, perhaps with PlaneImplementation=PerScanline (or PerPixel depending on your favorite implementation and the drivers' capabilities).
Three Plane elements defined with the proper colors, Appearance active.
2.a. The #2 device with an additional greyscale mode.
Implementation can vary.
It might just be an additional job command sequence. So you would create an additional ColorMode record with the proper entries (only the Command element would be different).
Not really complicated with a cautious implementation.
3. Hypothesis: There is a new device, which needs a true greyscale input.
Condition 1: the UPDF driver has to support a color to greyscale conversion. Do we expect a UPDF driver to do that?
Condition 2: The ColorMode record for greyscale would have one black plane (my personal opinion!), but no other planes.
Keep in mind that the Predefined_ID of ColorMode is meant to tell the operating system about the color capabilities. this attribute has nothing to do with what the driver is sending to the device!
Does that sound reasonable to you or do we just forget about #3?
You may take this as a case study to check the power and flexibility of the spec. Please contribute to the discussion. it educates us all.
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