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From "J.Pietschmann" <j3322...@yahoo.de>
Subject Re: Image Size Calculations
Date Tue, 08 Jun 2004 20:55:12 GMT
Darn, the mail server failed yesterday. Resending.

Peter B. West wrote:
 > I think the problem is that pixels are not well-defined.  In general, 
a pixel is an output-dependent unit.  On a printer, a pixel might be 
1/2400 inch, on the screen, 1/96".  The Recommendation warns about this 
in 5.9.13.1 Pixels.  I suggest that anyone tempted to define lengths in 
"px" read that section of the Recommendation.  It's not so bad if the 
units are completely "internal", that is, that it only affects text, 
tables and the like.  But when you import an image constructed 
externally, and defined in pixels for God knows what output device, you 
are asking for trouble.


Well, perhaps we should use wording like this in graphics.xml:

"FOP always assumes a resolution of 72dpi on encountering pixel
measurements, regardless of the output device, and converts all length
measured in pixels in millipoints using 1/72 pixels per inch as
conversion factor. The layout stage doesn't use pixels, even if the
final rendering is on a bitmapped device like the monitor. A bitmapped
image without explicit measurements is assumed to have the actual pixel
counts as measurements. Any resolution declaration in the image metadata
is ignored."

BTW does someone know how resolution is stored in GIFs, and whether
the Java image API can retrieve this?

 > Bottom line - don't define *anything* in px.

Yeah, double this. I have no idea why people are confused to no
end by this issue.

J.Pietschmann


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