how to calculate delta e for two areas ?

[talalzahid]

Hi all,

is it possible to calculate delta e for an area in photoshop? I do not want to use the sampler to get the values, I am using the histogram to get the area LAB or RGB values.

Thank you in advance

Taz

 

[IamSam]

Hello and welcome to PSG.

Take a look here: delta E

Here is one for Photoshop: https://feedback.photoshop.com/photoshop_family/topics/delta-e-calculator-in-info-palette

 

[thebestcpu]

Hi Taz

A clarification or your question might help with more specific recommendations.

Delta E is the 3D geometric distance between two colors measures in Lab space.

Since you mention the delta E of an "area", do are you trying to determine the maximum delta E between any two arbitrary pixels in that area, or the delta E of the average color in the area compared to another reference, etc.

Which two colors between which you want a delta E measurement.

Sorry, I may just being slow today understanding your specific needs

John Wheeler

 

[talalzahid]

Hi Taz

A clarification or your question might help with more specific recommendations.

Delta E is the 3D geometric distance between two colors measures in Lab space.

Since you mention the delta E of an "area", do are you trying to determine the maximum delta E between any two arbitrary pixels in that area, or the delta E of the average color in the area compared to another reference, etc.

Which two colors between which you want a delta E measurement.

Sorry, I may just being slow today understanding your specific needs

John Wheeler

Hi John,

I am trying to get the delta e for the average color between two areas (before,after) like the attached pictures

 

[thebestcpu]

Hi Taz

The steps below will tell you how to get the delta E between the average colors between the two areas.
I am skeptical that this is what you want since you have not described how this single number is going to be used. If you want to know how to convert on average how to convert from one image to the other, delta E will not give you that information. Rather you would want a delta Color Vector. So just a heads up about the delta E number

1) Your image data must be in a known color space e.g. sRGB, Adobe RGB, ProPhoto RGB etc and the image must be color managed in PS (note your images did not have a profile with them)
2) Convert both areas from the know RGB color space to Lab space using Edit > Convert to Profile
2) Independently for each area use the Filter > Blur >Average filter to create the average color over the entire area of each
3) Use eye dropper or color sampler tool and read the Lab values for each.
4) Calculate the root mean square using the two Lab values and you have your delta E

The following formula is specifically for LAB CIE76



Here is the link to the web page with many more details and other delta E models. I just provided you the one most commonly used: https://en.wikipedia.org/wiki/Color_difference

Hope that helps

John Wheeler