DeviceRGB, CMYK, & Gray color spaces are deprecated. You should
always
I'm alarmed to hear this. It seems that you will be breaking
applications
that need to access device colorspaces for the purposes of calibration
and profiling.
Let me clarify something. At last year's WWDC, we deprecated
DeviceXXX colorspaces. We had plans to introduce new colorspaces for
the common cases that people used DeviceXXX.
- A display colorspace for offscreen bitmap creation. (there is some
simple sample code to do this already though)
- UnCalibratedXXX colorspaces for exactly the case that you want (but
this is a very special need)
Unfortunately neither of these were made public by the time Tiger
shipped. So in Tiger, DeviceXXX colorspaces are really not officially
deprecated, because the replacements weren't ready. My comments above
for deprecation were really to get people to move off of DeviceRGB as
it is not needed for the majority of cases. We've been saying so
since 10.0 and would like people to tag their data always.
So how do I create a test chart in device colorspace to characterize
a printer ?
Even without the deprecation of DeviceRGB colorspace issue above,
this has not exactly been possible, because PDF documents on Mac OS X
will never write out Device colors and will replace source Device
colors with Generic. There has never been a mechanism available to
write out Device colors in PDF documents. Because PDF is the spool
file format on OS X, it's the only way to get your data to the
printer. The UnCalibratedXXX colorspaces were meant to allow
developers to generate PDFs with DeviceXXX colors. Until they are
available, the recommendation was to tag your data with the
colorspace of the destination device.
If one wants to avoid color matching, use the colorspace of the
destination device, if you know it.
This seems to be a unreliable way of handling calibration and
profiling.
It's known for instance, that many print drivers do not reliably
return the actual profile they will use for a particular print mode,
therefore matching the colorspace of the destination doesn't seem
possible.
It also makes calibration and profiling "fragile". It would be too
easy
to get the wrong profile, and result in creating a new invalid
profile.
If you create a test chart tagged with the current printer profile
for instance,
print it, create a profile and install it, then the saved test
chart will
no longer be usable for profiling. It will have to be re-generated
with the
new profile.
If a test chart is tagged with as being in device space, then
it will always be valid.
Understood, and the new UnCalibratedXXX were meant to address some of
this. Tagging with the destination space is still the interim solution.
Graeme Gill.
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