On Wed, 02 Sep 2009 13:31:33 -0700
Glenn Linderman <[email protected]> wrote:
| On approximately 9/2/2009 11:26 AM, came the following characters from
| the keyboard of Tyson Boellstorff:
| > Running ghostscript for windows 8.64, ImageMagick 6.4.9 Q16
| >
| > I have a number of scanners to support that throw their images into pdf
files
| > as streams. I'd like to convert them into tiff images. The resolution of
the
| > pdf 'envelope' is 72x72, appropriate for display on screen. The resolution
of
| > the scan can be anything from that to 1200x1200 (or greater). However, when
I
| > run convert or when I use Image::Magick to write the image out as a
| > multi-page tiff, the resolution of each image is now 72x72. Not good. This
| > also fails for conversion to png format.
| >
| > I can manually run gsview and display/print the pdf at the 200x200
resolution
| > with no problems.
| >
| > When I run
| > @Attribs=qw(width height x-resolution y-resolution);
| > $image=Image::Magick->new();
| > $image->read('test.pdf');
| > and loop through all the pages using this:
| > @attribvals=$image->[$i]->Get(@Attribs);
| >
| > @attribvals shows that the resolution is 72x72, and width and height
compute
| > out to scan size for each page.
| >
| > I can hard code these values to a better resolution, but more
appropriately, I
| > should be getting the resolution from the stream itself. Since Get() only
| > returns the 'envelope' size, how would a person get this information?
|
| Apparently the only way to do it at the moment, is mark down the actual
| scan resolution, and allow a parameter when running convert or
| Image::Magick.
|
| I researched this about and found nothing free, and then asked about
| this here and was told that while it is straightforward with commercial
| software to obtain this information, that no known free package provides it.
|
| Personally, I do my scans with IrfanView, and save as multi-page TIFF
| rather than PDF, which saves a step in my process, so I only have to
| convert those that are sent by other people that scan to PDF, and they
| don't tell me the scan resolution, so I always have to experiment or
| guess. Fortunately, those occasions are few.
|
| I don't know if you can convince your scanners (people, machines,
| software) to use IrfanView and save as multipage TIFF, but maybe that is
| worth investigating.
|
| Good luck, and if you are more successful than I at finding a free
| package, be sure to report back here.
|
The problem is PDF files don't have a specific resolution!!!!
they are ment to be vector images. but in this case it is a vector
image wrapper around a raster image.
I have not found a good way of extarcting a raster from a PDF (or
postscript) at its ideal resolution.
Anthony Thyssen ( System Programmer ) <[email protected]>
-----------------------------------------------------------------------------
How many programmers does it take to change a light bulb?
None. It's a hardware problem.
-----------------------------------------------------------------------------
Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/
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