23 Jul
2013
23 Jul
'13
11:02 a.m.
On Tuesday, July 23, 2013 at 11:04, Christian Corti wrote:
I had tried that in the past, but the result
weren't satisfying at all.
I've done many scans of HP manuals that way with good (if time consuming)
results. See, for example, the schematic on page 8-9 of:
http://www.bitsavers.org/pdf/hp/64000/hardware/64050-90901_Feb-1983.pdf
I have only a US-letter-sized scanner (HP 5590), so that 30-inch by 11-inch
page was made from four or five scans spliced together.
E.g. you'll never get the lines crossing the scan
boundaries to match.
I obtained good matches if I used a program that straightened each of the
partial scan images before assembly. No matter how carefully I aligned the
page on the scanner, there were always small angular displacements from
image to image. Joining them together without postprocessing would show
the problem that you mention. But after straightening, they would join
virtually seamlessly (i.e., with a displacement, at 600 dpi, of a pixel or
two across the image height).
And even fladbed scanners have a small "3D"
component in the result
that distorts the image especially around the edges of the scan area
and where the paper has folds.
I worked around the edge distortions by cropping the images before
assembly, although it often meant that one more scan was needed, as I was
only using the central 8 inches or so of the 8.5-inch scan.
My experience is that it is certainly possible, but it took me maybe 5-10
minutes of labor per wide page in cleanup and assembly to get good results.
-- Dave