I'm just trying to use my scanner as a copy machine.
I'm using Suse 10.3. This is not out of the dark ages. But I tested
convert test.pnm -set units PixelsPerInch -set density 300 test.png
on my wife's ubuntu machine with convert at
Version: ImageMagick 6.3.7 06/04/09 Q16
http://www.imagemagick.org
and got the same results. The identify of the output file is:
Image: test.png
Format: PNG (Portable Network Graphics)
Class: PseudoClass
Geometry: 2528x3509+0+0
Type: Bilevel
Endianess: Undefined
Colorspace: Gray
Depth: 1-bit
Channel depth:
Gray: 1-bit
Channel statistics:
Gray:
Min: 0 (0)
Max: 1 (1)
Mean: 0.97531 (0.97531)
Standard deviation: 0.155178 (0.155178)
Histogram:
8651735: (255,255,255) #FFFFFF white
219017: ( 0, 0, 0) #000000 black
Colormap: 2
0: ( 0, 0, 0) #000000 black
1: (255,255,255) #FFFFFF white
Rendering intent: Undefined
Resolution: 72x72
Units: Undefined
Filesize: 41.1934kb
Interlace: None
Background color: black
Border color: rgb(223,223,223)
Matte color: grey74
Transparent color: black
Page geometry: 2528x3509+0+0
Dispose: Undefined
Iterations: 0
Compression: Zip
Orientation: Undefined
Comment: SANE data follows
Density: 300
Signature: 66499efaa0bccb012c796c7491851d53b5e545bb32846cc0d3625796070e2c71
Units: PixelsPerInch
Tainted: False
User time: 0.450u
Elapsed time: 0:02
Pixels per second: 8.45981mb
Version: ImageMagick 6.3.7 06/04/09 Q16
http://www.imagemagick.org
The explicit suggestion of using -resize reminded me of the result of that particular test: using -resize A4 naturally didn't work. Using -resize 210 (where 210 is the width of A4 paper) presumably gives me an image that's 210 pixels wide...
Okay, thank you, you've helped me clarify my question. It was said,
(or "-resample", but for that you would have to update the density info first).
What's not clear to me is what the -density refers to - the real density of the input file or the real density of the output file?
I mean, my scanner scans at 300 dpi, my printer prints at 300 dpi, the scanimage(1) output file says 72 dpi, but when I just print the output file that I created with:
convert test.pnm -set density 300 test.png
I get a huge imagine over may pages of paper.
This must be a problem that a lot of people have - maybe they just don't know how to ask.