# How to calculate average color for some part of picture

I was looking for this answer here but didn't got exactly what I was looking for. Bit of context: I'm making some test printing forms, I want to see how colors are mixing when printed on Risograph. Risograph is sort of automated silkscreen printing technique automatized for printing on paper. It's using spot colors, so with overprinting you can get different colors. It's not easy as CMYK colors where you can just make any color you want and printer will figure out how to produce it.

So when I print my test card I get this:

I want to calculate average color from each square and get HEX or HSV value.

When I was searching for the answer I found this mkweb.bcgsc.ca/color-summarizer/?home but it can calculate average for the whole image. I know I can just cut small images and upload each one of them and calculate it like that but it will take me ton of time to do so. I will have around 60 images (like i posted) to calculate each square. I also found this tool www.gpick.org/ but if I understand correctly it can tell you average color for just few pixels around spot you click on, and I need it for squares that are 15x15mm.

I have to tell you I'm not a programmer, I used matlab in school one time but didn't understand anything. For me it would be great if I could achieve what I need with some end-user application like Photoshop, GIMP or anything where I don't need to learn coding.

Would appreciate any help!

Using Photoshop, you can use the color sampler tool and select a suitable sample size (for example 51*51 average).

• Thanks! This sounds like a good solution! Didn't know eyedropper can do this. Just one follow up question: "51*51 average" will calculate area of 51x51 pixels centered on the point where I clicked? – Trombolo Feb 4 '17 at 19:44
• Yes, the sample will be centered on your selection. – Olivier Feb 4 '17 at 22:51
• GIMP has something very similar. – Peter Taylor Feb 6 '17 at 12:30
• @Trombolo you'll want to use a linear color space to make sure the colors are averaged correctly. I'm not a Photoshop expert so I don't know how to set it up. – Mark Ransom Feb 6 '17 at 23:45

A more accurate sampling of the actual average would be in Photoshop, to draw a box around the selected sample (with regular marquee tool), and then use Photoshops averaging filter (menu Filters - Blur - Average). This gives one smooth solid color for the computed average (within that drawn box), so then the color picker tool will show this same average value, no matter where you click in the box you drew.

• Isn't it exactly what a big sample size will do ? – Olivier Feb 7 '17 at 6:47
• This method also allows you to calculate the average over any shape of selection, not just a box. 👍 – Nathan Reed Apr 10 '18 at 22:46

You might also look at ImageJ which is an open source, scientific image processing program. It has all sorts of analysis tools.

https://imagej.net/Welcome