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Image Replacement
Image replacement is a common practice utilized by graphic arts firms to provide
their customers with image files that are smaller in size and more manageable
for layout or display. High resolution images are replaced for final output
for production of the published product. The images can be replaced with the
use of the Open Prepress Interface (OPI) or Automatic Picture Replacement (APR)
processes.
OPI improves the performance of prepress systems by reducing data. The prepress
system is more efficient and is able to process information more quickly. Images
are scanned as high-resolution TIFF graphics and saved until they are needed
for output. A low-resolution TIFF version of the same graphic is created to
be used during the page layout phase for position only (FPO). Using the TIFF
version makes layout much more efficient because the low-resolution graphics
require a smaller portion of the computer's resources, allowing it to operate
more efficiently. When the layout is complete and ready for output, the low
resolution TIFF images are automatically swapped with the high-resolution versions.
The replacement of the images takes place on the print server just before the
file is sent to the RIP (Raster Image Processor).
APR works much the same as OPI except it uses high-resolution Scitex CT (continous
tone) files or TIFF and EPS files. A low-resolution EPS file is used as the
replacement image during design and layout. When the layout is ready for output,
the low-resolution images are replaced with the high-resolution versions. The
image replacement takes place at the RIP rather than at the print server.
The following points should be considered when working with replacement images:
- Any image corrections should be corrected on the original high-resolution
image.
- The file names and formats should never be changed or the link will be lost.
- The original image should be sized and rotated before the low-resolution
version is created and it should not be changed afterwards.
- If minimal scaling is required, it can be accomplished in the page layout
program, but if it is more than 20% either way, the image should be rescanned.
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