Re: Screen shot fallacies

["Thomas Michanek" <thomas.michanek@xxxxxxxxx>]

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----- Original Message ----- 
From: "John Root" <jroot@publisys.com>
> Just to clarify what seems to be poorly understood.
> The resolution of objects displayed on any Windows platform is 96dpi (72dpi
> on Mac). This is independent of display resolution. As a result, any screen
> shot from a Windows display will be 96dpi.

This makes no sense at all (to me). DPI stands for "dots per inch", meaning
display pixels per inch in the case of screen images. No object displayed
on a computer monitor has an "inherent" resolution independent of the
display resolution. If you claim this is the case, then explain what a
"virtual inch" is. A computer monitor displays a certain number of pixels
per inch on the screen. If you change the monitor's resolution (number of
pixels displayed), then you change the displayed DPI.

> Screen captures are taken directly from the computer's display memory,
> not from the monitor itself.

Correct, which is why a screen capture doesn't have an associated DPI value.
As an example, a GIF file for a screen capture stores the pixels making up
the screen image (and their color values), but you won't find any information
in a GIF file about "resolution" or "dpi" or physical size in inches.

When you import a bitmap image into FrameMaker, the DPI value you select
has nothing to do with the displayed DPI, and FM has no idea whether the
image was taken from a Windows screen, a Mac screen, or a SUN screen.
The DPI value refers to the resolution of the image when *printed*,
which is why you should select a DPI value suited for the output device.
If you don't believe this, check the pixel dimensions of the image and
how much space it occupies according to the ruler in FM (or print it out
and measure the printout). Do the math and you'll find that "pixels per
inch" correspond to the DPI setting in FM, regardless of how much screen
size the image occupies, or the "resolution" of your monitor.

If you change the zoom value in FM, or the monitor size preference, the
size of the image on-screen will change. Therefore, the DPI value has
nothing to do with the display DPI. The image size changes to correctly
reflect the physical size when printed.


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Thomas Michanek, FrameMaker/UNIX/MIF expert
mailto:Thomas.Michanek@telia.com   (Sweden)
http://go.to/framers/  (updated on Oct. 11)
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