| Blurred display of images in PDFs created from EPS on Mac OS X [message #42304] |
Thu, 03 February 2005 09:03  |
jm
Messages: 32
Registered: April 2003
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I often make false colour maps of data in IDL and export as EPS
graphics which I used to import into FrameMaker documents. I have
recently migrated from Solaris to Mac OS X and plan to use Pages and
Keynote (I know, Pages is not a FrameMaker replacement, but that
another story.) Anyway, there is an irritating quirk in the way Mac OS
X displays the PDFs created from EPS files - the image embedded in the
graphic (say, a 20 by 20 array) is displayed upsampled and horribly
blurred. This is the case in Preview and Keynote, but not Acrobat 7
which shows it nice and crisp. Keynote shows the PDF image blurred in
editing and as a slide-show, but it does export a sharp PDF. Whilst
this is workable, it does mean not using the native Keynote slide-show
mode.
This is evidently a Mac OS X quirk, rather than anything to do with
IDL. However, despite some searching, I can't find any mention of it
any of the Apple lists etc. Furthermore, it may be something that only
occurs with arrays (i.e. images) embedded in EPS files - something IDL
users are likely to produce, which is why I've posted here.
Any ideas?
-John Mardaljevic
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| Re: Blurred display of images in PDFs created from EPS on Mac OS X [message #42416 is a reply to message #42304] |
Mon, 07 February 2005 08:17  |
Norbert Hahn
Messages: 46
Registered: May 2003
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jm@dmu.ac.uk wrote:
> The false colour map (byte-scaled array) is displayed (written to the
> Postscript device)
> using TV just like any other image. It just happens to have small
> pixel dimensions.
Maybe your program mis-interprets some PostScript elements, such
as pixmaps? If I understand PS correctly there is no such thing
as a pixel on the input side of PS. A bitmap fed into PS is an
area which has to be filled with scalable rectangles. When printing
the PS engine (of course) has to translate the rectangles into
device pixels, and it might apply some low pass filtering to avoid
moiree.
Maybe the PS generator of IDL did something to fool your program.
I used the following program for a check:
IDL> set_plot, "PS"
IDL> tvscl, dist(20,30), xsize=5, ysize=5, /inch
% Compiled module: DIST.
IDL> exit
That resulted in PS code that looks like (the comment lines
are my interpretation):
%% Setup scaling 72/2540 as needed for a device with 2450 DPI res.
$IDL_DICT begin 54 360 translate 0.0283465 dup scale
%% Scale a 20x30 bitmap to 5x5 inch ( 12700 pixel on output)
12699 12699 scale 20 30 4 [20 0 0 30 0 0]
%% use the image operator to input the matrix
/J { currentfile picstr readhexstring pop} bdef
{J} image
001234567787765432100112345678887654321111233456789876543321 223
[snipped]
... which looks correct to me.
How did you define the size of the area that TV should fill in?
Regards,
Norbert
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| Re: Blurred display of images in PDFs created from EPS on Mac OS X [message #42481 is a reply to message #42304] |
Wed, 09 February 2005 02:22 |
jm
Messages: 32
Registered: April 2003
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> I sent an example to my local Apple customer engineer. He can see
that
> Adobe Reader (for example) and Apple programs such as Preview and
> Keynote display images differently (both on OS X). He is sending a
> request up the chain to have the image smoothing turned off, or at
least
> made optional.
Thanks, Ken. I think someone at RSI may also bring it to Apple's
attention.
I'm sure that it will take a few nudges to get this noticed by Apple.
-John Mardaljevic
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