[texhax] Img quality in pdf

[William F. Adams]

On Feb 4, 2005, at 12:36 PM, tomlobato wrote:

> in Gimp, I cannot see dpi conf when creating a new image, but I can set
> resolution, and the default is 72x72. How to obtain 300 dpi? Just 
> setting
> 300x300 in resolution? Well, as you can see, I need some more theory, 
> where
> do I find a good doc for learn this?

The best option then is to redraw it in a print-oriented vector 
graphics program such as Cenon, Skencil, InkScape or Sodipodi (the free 
options), Macromedia Freehand, or Adobe Illustrator for commercial 
programs.

>> The .jpg is 322 x 213 pixels/points (@ 72dpi) and when placed in the
>> .pdf is exactly the same.
>>
>> The perceived difference in quality is that when viewed on-screen as a
>>
>> .jpg it\'s displayed at 1 pixel in the image per one pixel on-screen.
>> When you place it in a .pdf, unless you view it at 100% on a display
>> coordinate system set to 72 dpi there\'s going to be scaling /
>> interpolation which results in a less than perfect representation.
>
> But when I see the final pdf document at 100%, I can see some 
> differences in
> two images: Look the blue lines linking the computers and and the 
> borders of
> the light blue rectangles in http://soc.if.usp.br/~tlobato/pdf, in the 
> pdf,
> it is zigzag, and in the orginal jpg, not.

Look at the .pdf @ 100 % on a system for which the coordinate display 
system is 72 dpi --- a Mac w/ Acrobat will work for this, and the image 
in .pdf looks exactly like the .jpg when displayed thusly.

Or, bring up the .jpg in a web browser. Bring up the .pdf in a .pdf 
viewer. Zoom in / out on the .pdf until the image is displayed at 
_exactly_ the same size --- you'll then see that the quality is 
identical.

William

-- 
William Adams, publishing specialist
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