Subject: TIFF-FX Profile M (MRC) on an embedded system?

From: "John Pulera" <[email-masked]>
Date: Wed, 18 Oct 2000 11:30:37 -0700

Dear IETF-Fax group,

            I am in the course of implementing an embedded imaging system
with TIFF-FX capability, and am wondering if anyone else has run into
similar concerns in supporting "Profile M" Mixed Raster Content (profile is
described in RFC2301) on an embedded system:
            The 3-layer "Mixed Raster Content" as it is described in
RFC2301, calls for support of a mask layer (1bpp), background layer
(multi-bpp), and foreground layer (multi-bpp). When the Mask layer pixel
value is 1, the corresponding pixel from the Foreground layer is selected;
when it is 0, the corresponding pixel from the Background layer is selected.
Thus, for three-layer MRC, the following Boolean equation describes any
given pixel value:

            Q = (M AND F) OR (M' AND B)

where Q is the output pixel value, M the Mask layer pixel value, F the
Foreground pixel value, and B the Background layer pixel value. The problem
is all three layers cannot be logically applied, one after the other, to
obtain the final image. M appears twice and therefore needs to be retained
during processing of both the Foreground and Background layers.

Due to the “planar” style in which each layer is found within a Profile M
TIFF-FX file, a reader’s options are not very appealing:

a)      Retain the uncompressed Mask layer in memory during processing of
the Foreground and Background layers. With currently allowable TIFF-FX
bi-level resolutions of up to 400 dpi, this would mean buffering up several
MB of data in memory.

b)      Constantly “ping-pong” between the mask layer and Foreground or
Background layer. This would present TIFF-FX reader with much overhead as it
would have to constantly reset the graphics and decompression states based
on the IFD values for each layer. Such a strategy also assumes there is a
small enough difference in file offset between the Mask and the Foreground
or Background compressed band data.

Any response on this matter is much appreciated.

Thanks,

John Pulera
Minolta Systems Laboratory
[email-masked]