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From "Peter B. West" <pbw...@tpg.com.au>
Subject Re: Image Size Calculations
Date Mon, 07 Jun 2004 15:20:04 GMT
Clay Leeds wrote:
> On Jun 7, 2004, at 2:13 AM, Chris Bowditch wrote:
> 
>> Christian Hattemer wrote:
> 
> If it's true that graphics measurements specified in INCHES yields 
> better results than PX, that certainly is news, and would (if 
> reproducible) warrant special mention on the FOP Graphics page. Can you 
> also do a test to see if the results are similar if you specify mm and 
> cm (millimeters & centimeters of course ;-)) as well?

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.

Consider the lengths that Gimp goes to on installation to make sure that 
images are reliably sized.  You must effectively tell Gimp exactly what 
the size of a screen pixel is on your monitor.  Incidentally, if you 
want to find out about the dimensions of images, install Gimp and load 
the image.  Because of Gimp's awareness of your monitor size, you should 
be able to get reliable translations of image sizes into stable units.

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

> BTW, I don't know if this is related, but GIF images do not scale well, 
> as they are a form of a INDEXED BITMAP image. JPG images scale much 
> better. This could be part of the problem. If you're working with line 
> drawings, perhaps SVG might be a better format to use in your documents.
> 
>>> This leads to the question: How can I find out the actual resolution 
>>> of my
>>> images and calculate the dimensions in inches? Do I have to modify the
>>> generated fo afterwards to include the calculated dimensions?
>>
>>
>> Dont you know the resolution of the images? It is difficult for me to 
>> answer this question as I dont know where you get the images from. In 
>> my environment, the system responsible for generating the images 
>> stores the measurements in cm/mm/inches along with the resolution and 
>> the image itself.
>>
>> Chris
> 
> 
> Can't you just load the image directly into a web browser:
> 
>>> images/NetworkModel/Basics/BachmanDiagram.GIF
-- 
Peter B. West <http://www.powerup.com.au/~pbwest/resume.html>

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