# scanners that do jpeg compression

Stephen Williams (steve@icarus.com)
Thu, 29 Jul 1999 19:58:49 -0700

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I have a whole bunch of high-performance scanners that are just
screaming for SANE drivers. Some are color, some are grayscale.
All can produce many views (i.e. color and binary) of the same image,
and all compressed the image in hardware.

I see that SANE is going to have some troubles with these scanners.
It is reasonable to expect the driver to decompress these images and
present them to the default application as RGB images, but I would like
to write SANE applications that can receive these images as JFIF streams.
The program may save them to disk, or preview the image, or both, but I
would like to give a JFIF aware application the JFIF frame.

For the particular scanners I have in mind, it is imperative that the
image not be decompressed/recompressed unless it is to be displayed
or passed on to non-compression aware applications. Otherwise, there is
simply no chance of getting the 180PPM that some of these scanners can
operate at.

To accomplish this I can see obviously that I can create a driver
option that enables JFIF frames. However, if the user does this, I do
not see how to communicate with the application that the comming frame
is JFIF. The scan_get_parameters result includes the format, and I see
no way to express that the image is arriving compressed.

TWAIN supports compression of frames, as does Pixel Translations Pixtools.

So, what's a high performance scanner producer to do?

    --
    Steve Williams                "The woods are lovely, dark and deep.
    steve@icarus.com              But I have promises to keep,
    steve@picturel.com            and lines to code before I sleep,
    http://www.picturel.com       And lines to code before I sleep."

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