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10-17-2019, 04:30 PM   #1
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Can I draw a box in RawTherapee and get the average of the pixel values therein?

A question for all the RawTherapee mavens here:

In PhotoShop (Elements, at least - that's what I have) and Darktable, I can draw a box within an image frame and have the software report the average R, G, B values of the pixels within the box.

Can I do that in RawTherapee? If so, how? If I move the cursor around, I can see the RGB values for whatever pixel I happen to be over, but I'd rather see an average value over a number of adjacent pixels.

10-17-2019, 04:53 PM   #2
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No way to do that as far as I can tell (I've been using RT for several years). I also searched Rawpedia to be sure.

One hack you might try is to activate wavelet levels and view the residual image (background Residual, process one level, Residual). You'll get a really blurry image that might give you a local average, but I'm not sure how accurate that would be.

You could ask on discuss.pixls.us, you might get a better answer--or might interest one of the developers to implement your suggestion...
10-17-2019, 04:54 PM   #3
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How about:

1) draw a box, copy that rectangle, make "new image from clipboard," and then downsample to 1x1?

2) use a standalone utility: Mac OS has the "Digital Color Meter" that reports the RGB value of a small square up to 11x11 pixels. (Other OSes probably have something similar)
10-18-2019, 07:48 AM   #4
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I'm still very basic in my post depth and skills. What do you do with this value once you have it?

10-19-2019, 03:41 PM   #5
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Sir Nameless & photoptimist: thanks for the suggestions. Some kind of averaging should work - hadn't thought of that. I don't care what the resultant image looks like, I just want a reasonable average value in the middle of a Gretag-Macbeth color square.

QuoteOriginally posted by clickclick Quote
I'm still very basic in my post depth and skills. What do you do with this value once you have it?
This is part of my efforts to determine how RAW data values get scaled by various programs (RawTherapee, Darktable, Photoshop Elements at least), as a follow up to this study: How Linear Are Some Pentax Camera Sensors? - PentaxForums.com
10-19-2019, 07:12 PM   #6
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I’m fairly certain that RawTherapee does not do any behind the scenes scaling, so what you see with the tone curve is what you get. So with a neutral processing profile set, you should see a linear scaling between the raw data and the output.
10-19-2019, 08:51 PM   #7
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QuoteOriginally posted by AstroDave Quote
Sir Nameless & photoptimist: thanks for the suggestions. Some kind of averaging should work - hadn't thought of that. I don't care what the resultant image looks like, I just want a reasonable average value in the middle of a Gretag-Macbeth color square.



This is part of my efforts to determine how RAW data values get scaled by various programs (RawTherapee, Darktable, Photoshop Elements at least), as a follow up to this study: How Linear Are Some Pentax Camera Sensors? - PentaxForums.com
Thanks

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