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Re: Image processing question [message #30840 is a reply to message #10214] Mon, 20 May 2002 17:11 Go to previous message
btupper is currently offline  btupper
Messages: 55
Registered: January 2002
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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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