On Fri, May 17, 2013 at 12:15 PM, Brickle Macho <bricklemacho@gmail.com> wrote:

I porting a 8 line Matlab script.

<snip>

So what is the difference between converting an array to gray scale verse reading it in as grayscale? Have I done something wrong? Is there another way to convert a numpy array to grayscale?

Any help appreciated.

Michael.
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Hi Michael,

They're just different color conversion factors. Based on http://www.mathworks.com/help/images/ref/rgb2gray.html, Matlab uses:

0.2989 R + 0.5870 G + 0.1140 B

Based on the docstring for `color.rgb2gray`:

0.2125 R + 0.7154 G + 0.0721 B

Wikipedia (http://en.wikipedia.org/wiki/Grayscale) seems to suggest that Matlab's is an older standard while the one in scikit-image is a more recent spec.