6 Replies Latest reply on Nov 19, 2012 6:30 AM by rob day

Color match area

I have a B&W pic I'd like to sum the overall grayscale values into one number and create a swatch from this. How would one do this?

• 1. Re: Color match area

With Photoshop, perhaps. Blur-and-blur-some-more until your image is all but a gray blur. Then measure it.

• 2. Re: Color match area

PhotoShop's Histogram panel in expanded view gives the median pixel value. So in this case it would be 100|100|100 RGB:

• 3. Re: Color match area

It shows a value "100", so I'm guessing this is not a percentage . So this must be in 1/256ths? Or, if the maximum value for all-white is "255", 1/255ths?

Wait -- that cannot be right, I just called up a simple graphic (black lines on white background) and it shows "255". Maybe you should look at the "Mean" value, 2 items up? Statistics is one of the few fields of maths in which I'm surprisingly bad, I could not recall the difference between Mean, StdDev, and Median if my life depended on it ...

• 4. Re: Color match area

You're right Mean is the average.

• 5. Re: Color match area

<g> I tried my blur/blur/blur/and blur even more, but it doesn't lead to anything useful after all.

Since the Mean is "109.88" in your image, I suspect this isn't a percentage either If it is 1/256ths, there still is a lingering question ... Luca wants a grayscale swatch, which is measured as a percentage of [Black], that is, 0% is white and 100% is full black.

So would the value needed be 109.88/256 * 100% = 42.9% [Black] or does Photoshop measure "the other way around", as usual for RGB, and is the value of Black therefore 100 - 42.9 = 57.1%?

• 6. Re: Color match area

Black therefore 100 - 42.9 = 57.1%?

I think that's probably right. Photoshop's Curve dialog lets you choose between 8-bits and ink percentage: