| Image processing question [message #10214] |
Mon, 27 October 1997 00:00  |
Eric Williams
Messages: 14
Registered: April 1997
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Junior Member |
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Hello,
This might not be specific to IDL, but I am using IDL for this work so I
thought I would ask the experts. I am looking for a reference or source to
read up on processes for combining a series of images. The images will need
to be shifted to match up objects (specifically stars) and use the best
algorithmn to do the adding. This is a common procedure in astronomy, but I
haven't found any "instructional" material that explains the possible
options to perform this operation.
Of course if anyone has written code that already does this I would be
interested in checking it out.
Thanks,
Eric
eric@astro.wesleyan.edu
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| Re: Image processing question [message #30840 is a reply to message #10214] |
Mon, 20 May 2002 17:11  |
btupper
Messages: 55
Registered: January 2002
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Member |
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On 18 May 2002 10:51:31 -0500, Craig Markwardt
<craigmnet@cow.physics.wisc.edu> wrote:
> rkj@dukebar.crml.uab.edu (R. Kyle Justice) writes:
>
>> How do I convert a color image(.jpg) to grayscale?
>>
>> I am using PV-Wave's Image_Read function to read the image,
>> which stores all the image info in an associative array.
>> Do I simply take the maximum RGB intensity value at each
>> pixel in the 'pixels' array (xdim,ydim,3)? This gives me
>> a grayscale image, but I'm not sure this is the "correct"
>> one.
>
> There is no one "correct" conversion from RGB to grayscale, since it
> depends on the sensitivity response curve of your detector to light as
> a function of wavelength. A common one in use is:
>
> Y = 0.3*R + 0.59*G + 0.11*B
>
If you are converting to the Hue, Saturation and Value (HSV) color
system, then the MAX of the RGB triplet will give you the Value image
(I have also seen this refered to as the Intensity image.)
Ben
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