Re: [Gimp-print-devel] What direction should we be headed?

[Michael S. <mi...@ea...>]

Thomas Tonino wrote:
> ...
> Ghostscript - or any other application for that matter - could use
> an output format that basically says 'print this pixmap here and
> print that little bit there' and pipe it to our driver. By using
> smaller pixmaps (or maybe even parts as bitmaps which will be
> rendered in black or some other color) we may keep performance okay
> as we do not send all the 'white' through the interface. I have a
> feeling Ghostscript is doing this internally already.

Check out CUPS - http://www.cups.org

We've done exactly this with our "pstoraster" filter, which is
GhostScript without all of the extra drivers and with a new frontend.

We also provide an "imagetoraster" filter that takes image files,
does bilinear interpolation on them, and spits out a raster image.

These filters are used to produce raster images for non-PS printer
drivers, which can then do any dithering, etc. needed.  The filters
also support limited color management based on sRGB color
transform matrices and a unified gamma/density lookup table, and
at some point in the future will support real ICC profiles.

Currently the entire page image is sent - detecting blank areas is
easy and fast, although we've considered modifying the file format
in the future to support blank suppression in Ghostscript if it
becomes a performance problem (it hasn't so far, even when printing
44" wide at 1440x720 DPI with our Stylus Pro 9000 driver)

> ...
> I think a form of concensus is needed: we all need each other.
> Interfaces would help: we'd have a low level driver interface and
> probably various application interfaces. Then there are 2 network
> interfaces right now.

The CUPS driver interface is pretty straight forward, and the image
RIP and raster function code is all GPL'd in CUPS...

Oh, and you'll find data fields in there that can be used to describe
the needed softweave parameters, etc. for the driver (that's what we
use for our Print Pro drivers)

> ...
> Ghostscript allow folks to change some command line parameters
> through (say) PostScript comments? Should save lots of folks all
> those printer queues for 300 dpi, 600 dpi, color, etc.

Why indeed? :)

It is possible to change the resolution, etc. in the PostScript
code:

    <</HWResolution[720 720]>>setpagedevice

This will set the hardware resolution to 720x720 DPI.  Commands
such as these are provided in PPD files, which the print plug-in
supports already to a certain extent, but unfortunately most
applications do not.

However, let me point out that sending images from GIMP as
PostScript to be interpreted by Ghostscript is a very inefficient
method of printing, and doesn't offer much in terms of quality.
Ghostscript doesn't support interpolation of low-resolution
images, and it very slow when it has to halftone those images.

-- 
______________________________________________________________________
Michael Sweet, Easy Software Products                  mi...@ea...
Printing Software for UNIX                       http://www.easysw.com