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Xerox 4112/4127 Copier/Printer User Guide
3-49
3. Scan
MRC High Compression Scanning
MRC, or Mixed Raster Content, is a compression model that
separates an image into three different layers: foreground,
background, and mask. Each layer is compressed separately
using the most appropriate type of compression for that data type
and is later uncompressed and recombined based on the mask
layer to restore the original image.This compression model is
available only when using the PDF Scan Kit.
As an example, consider a document with text, photographs and
graphical elements. Using the MRC High Compression model we
might place photographic elements in the Background layer,
colored graphical elements (including text color) in the Foreground
layer, and text shapes (or other similar high frequency, high
contrast elements) in the Mask layers. Since text carries visual
information at high contrast and spatial frequency, it can be
encoded as 1 bit per pixel at 600 spi. The values of 0 and 1 for the
Mask layer indicate which of the two other layers should be used
for reconstruction of the composite image.
In contrast to text, the accurate communication of photographic
and colored graphical visual information requires fewer pixels per
inch (lower spatial frequency), but requires more bits per pixel. To
compress the image, we would use a binary and typically lossless
algorithm, e.g., MMR, while the Background and Foreground
layers would be compressed using a continuous tone, and
typically, lossy algorithm, e.g., JPEG.
Using MRC High Compression will generally produce a smaller file
size than using one of the other compression models. You can use
MRC Compression on its own or with the other compression
models for additional compression scenarios.
NOTE: The following conditions should be considered when
using the MRC High Compression feature:
• MRC High Compression is not available for Color Scanner Kit
Black & White jobs.
• MRC High Compression is supported for 200 or 300 dpi scans,
only.
• When MRC High Compression is designated, document type
options are not available. The device automatically scans the
document in the Text/Photo mode.
• Photographic paper scanning is not supported with the MRC
High-Compression feature.
• PDF v1.3 is output in the MRC High Compression feature, and
documents can be opened by Acrobat 4.x, or later. When
JBIG2 is used for the compression method of the mask image,
PDF v1.4 is output.