[Scribus] Pre-use question about Scribus and a certain PNG image
jwminer at accessvt.com
Wed Jul 25 07:24:55 CEST 2007
> The resolution of the image is too low for printing, only 72 dpi.
> You need at
> least 200 dpi, better 300 dpi. The reason it looks worse in full
> is that its "flaws" become obvious.
Whoa! There is no such thing as absolute "72 dpi resolution."
Resolution is the pixel count divided by the output size. The pixel
count of the image is 2235 pixels wide by 501 pixels high. Dividing
501 by 1.9 inches (the height of the frame) gives a resolution of
263 dpi--well over your recommended 200 dpi. The frame I tried it in
is 7.5 inches wide. 2235 pixels divided by 7.5 gives a resolution of
298 dpi. So the resolution is NOT too low for printing. Well, on
what is essentially line art, a resolution of 600 dpi to match the
laser printer would be better (assuming it's a 600 dpi printer).
Line art looks best if the dpi matches the resolution of the output
So why is the resolution given as 72 dpi when you open the image in
an editor like the Gimp or Photoshop? It's because the image doesn't
include desired dimension, just pixels. In that case image editors
assume a conventional resolution of 72 dpi for screen output. Look
at the assumed size in inches of the image: approximately 31 inches
by about 7 inches! If you up the resolution to 300 dpi *without*
interpolation (in other words, keep the same file size), the
dimensions are now 7.45 inches by 1.67 inches. You have not in any
way changed the picture; you have simply given it smaller dimensions
than it had at 72 dpi. Therefore, the pixels are smaller and the
picture looks better.
I'm surprised that this fact was missed on a DTP list. Dpi in itself
means nothing unless you know the dimensions of the image. Pixel
count is everything.
Registered Linux User #397786
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