ImagesLowResolutionOnly 72dpi Jpeg Med v7.0.0
Apogee Preflight Action List
Agfa Apogee Prepress 7.0 and higher
What it does:
The Apogee Prepress action ap_ImagesLowResolutionOnly-72dpi-Jpeg Med v7.0.0 will downsample all images to 72dpi to produce a low resolution PDF file at computer screen resolution.
8 bit images will be downsampled using the "Average" method: The value of the new dots is calculated on the basis of the average of the pixels in the sample.
1 bit images will be downsampled using the "Bicubic" method: The value of the new dots is calculated on the basis of a weighted average of the pixels in the sample area. This method offers the best results with smooth tonal gradations, but takes the longest to calculate.
Compression:1 bit images will be compressed to CCITT
8 bit images will be compressed to Jpeg (Medium compression, medium quality)
16 bit images which cannot be compressed to Jpeg, are compressed to ZIP.
The CCITT compression method is best suited for black-and-white images made by paint programs, as well as for images scanned with an image depth of 1 bit.
CCITT is a lossless compression method, which means that no information is removed from the images during compression.
The JPEG (or jpg) compression method is best suited for grayscale or color bitmap images.
A typical example of an image for which JPEG compression is advised is a continuous-tone photograph. This type of image contains more information, more details, than can be reproduced on screen or in print. Therefore, it makes sense to remove the information that cannot be displayed anyway.
This can result in a loss of image quality, as the compression method removes information: it is called a lossy reduction method.