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FIG. 3: From left to right, the original image (23,800K), the Fax Group 4 image (162K), the JPEG
image (158K), and the LuraDocument image (64K). Images reprinted with permission from
LuraTech, Inc. LuraTech(R) and LuraWave(R)are registeredtrademarks of LuraTech, Inc. and
LuraTech GmbH.

Original Image
(23,800K)

Fax Group 4 Image
(162K)

JPEG Image
(158K)

LuraDocumentImage
(64K)

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FIG. 4: The LuraDocument dialog box provides control overhow each document will be com-
pressed, and in what form. (Screen capture courtesy of LuraTech, Inc.)

The composition of the digital original has a bearing on how it will be compressedinto a
LuraDocument file. The Photoshop plug-in provides several options related to that process.
According to the LuraDocument user manual:**

Coding Mode: Selects the layers of the LuraDocument image which should be saved.

Save Everything: Saves colored text and the background.
Save Text Only: Saves black text without the background.
Save Image Only: Saves only the background image (without text). Any detected
text is removedfrom the image.
Save Image and Black Text: Saves black text and the background.

The default value is Save Everything.

Text Detection: This switch chooses the method of segmentation, in other words, how
text is detected.

Automatic text detection with inverse text. For a document with text, images,
and background.

Automatic text detection. Automatic segmentation which only detects dark text.
Everything is text. Most conservative setting. Everything dark will be identified
as text.
Everything is image. For pure images containing no text.

The default is Automatic.

Quantization:

Adaptive. Quantization method which adaptively calculates the optimal threshold
betweenwhite and black.

Constant. Fixed value in the range 0…255 used as the threshold between white and
black.

The default value is adaptive.

Compression Factor: Indicates the requested compression factor (high to low). It is
possible that this compression factor is not achieved due to the complex nature of a
document. In this case the text layer is compressed losslessly and the text color and
background images are compressed using the minimal quality.

The default value is 1:1000.

Bitonal Coder: The bitonal text layer can be coded to use a Fax Group 4 coder by setting
the fax coder.Selecting fax compression lets the text layer be viewed using a wide range
of image viewer programs.

In the default case the LuraDocument®-Formatis used, offering higher compression in
comparison to Fax Group 4.
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**LuraDocument Software Photoshop Plug-In user manual. LuraDocument Document
Compression. LuraTech GmbH, Berlin, August 29, 2000, pages 18-20.

A LuraDocument is viewed in a supporting viewer,such as Photoshop, which combines the
three images into a decoded document. Each of three constituent file parts can be viewed
separately if necessary.