| Re: jpegs and tiffs [message #57789] |
Thu, 27 December 2007 13:08 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Josh writes:
> This makes sense -- unfortunately neither solution worked. I tried
> both
> quality=100 and RED='0000FF'XL (as well as both at the same time) and
> I always
> get two apparently black lines in the jpeg, but a colored line in the
> tiff.
> When I try LTGRAY='CCCCCC'XL, the jpeg does show the line as being
> light
> gray. It seems that the jpeg understands grayscale.
Humm. Sure you are using a 24-bit display? What does
HELP, /DEVICE tell you? What application are you using
to view your JPEG files?
Color! Scheesh!
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: jpegs and tiffs [message #57792 is a reply to message #57789] |
Thu, 27 December 2007 13:00  |
Josh
Messages: 21
Registered: June 2007
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Junior Member |
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> Well, I don't think there are *really* two black sine
> waves in the JPEG file. I think one of them is very dark
> blue and the other is black. But, you are right, it is
> not as blue as it is in the TIFF file. I think this is
> probably because of the "lossy" nature of JPEG files.
> I would try setting the QUALITY keyword on the WRITE_JPEG
> command to 100 and see if that doesn't help some.
>
> In any case, if you choose a RED color, you will see that
> you are getting differences in your two lines. :-)
This makes sense -- unfortunately neither solution worked. I tried
both
quality=100 and RED='0000FF'XL (as well as both at the same time) and
I always
get two apparently black lines in the jpeg, but a colored line in the
tiff.
When I try LTGRAY='CCCCCC'XL, the jpeg does show the line as being
light
gray. It seems that the jpeg understands grayscale.
J
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| Re: jpegs and tiffs [message #57819 is a reply to message #57792] |
Mon, 24 December 2007 18:36 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Josh writes:
> The following program is supposed to write two sine waves, a blue one
> and a black one, to two different files. However, on my system, the
> jpeg ends up with two black sine waves, whereas the tiff (as well as
> the window on the screen) end up with a blue one and a black one as
> desired. Any thoughts? Code is taken from Gumley, but with many
> changes.
Well, I don't think there are *really* two black sine
waves in the JPEG file. I think one of them is very dark
blue and the other is black. But, you are right, it is
not as blue as it is in the TIFF file. I think this is
probably because of the "lossy" nature of JPEG files.
I would try setting the QUALITY keyword on the WRITE_JPEG
command to 100 and see if that doesn't help some.
In any case, if you choose a RED color, you will see that
you are getting differences in your two lines. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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