# Image Intensity

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M@lik Ali on 4 Jun 2012
Commented: Walter Roberson on 10 Sep 2020 at 20:27
Hi all, Can any one tel me the command in matlab to calculate the intensity of image.

Jean on 5 Jul 2013
Does anyone further know how to do this for a specific area of pixels? For example, image(100:1:200,100:1:200) for a 100 by 100 pixel area, and get the intensity in this area as an average?
Image Analyst on 5 Jul 2013
meanGrayLevel = mean2(yourImage(100:200,100:200));
Don't use "image" as the name of your variable since it's a function.

Image Analyst on 4 Jun 2012
The mean of a particular pixel is just simply the pixel value, since there is only one sample - nothing really to take the mean of:
intensityValue = grayImage(100, 230);
meanIntensityValue = mean(grayImage(100, 230));
Here, of course meanIntensityValue will equal intensityValue.
To get the mean of all the pixel values in the entire image, you can do any of these:
meanIntensityValue = mean2(grayImage);
meanIntensityValue = mean(grayImage(:));
meanIntensityValue = mean(mean(grayImage));

Samantha Villanueva on 9 Sep 2020 at 13:45
hello can I use this to a colored image?
Image Analyst on 10 Sep 2020 at 16:36
You would have to do it on every color channel independently:
[r, g, b] = imsplit(rgbImage);
meanRed = mean2(r);
meanGreen = mean2(g);
meanBlue = mean2(b);
Walter Roberson on 10 Sep 2020 at 20:27
As the question is about mean intensity, then which definition of "intensity" do you want to use for your RGB image?

Adina Stoica on 4 Jun 2012
Well, the intensity of the image is the average of the intensities of all pixels in an image (unless you're doing anything more specific than that). So if you do
mean(imagefile(:))
you should get the intensity of the image.

#### 1 Comment

M@lik Ali on 4 Jun 2012
But actually i want to calculate the intensity value of all elements of the images.
someone told me like
intensityValue = grayImage(100, 230);
But in i have to calculate the intensity value of each pixel or total image, i think i can do it by calculating the intensity of each pixel and then add it but i am not sure.

Saranya on 30 Jan 2014
hi image analyst i want to measure the intensity profile for gray scale image.. can you help me..?

Walter Roberson on 20 Mar 2017
It looks like you just have to pick either a representative pixel or a representative level and call graydiffweight() passing in the data and the location or level.
Rasika Devi on 21 Mar 2017
Thank you so much sir.. One more thing from that weight value,how do i perform the image segmentation by using any algorithm? kindly help me...
Walter Roberson on 21 Mar 2017
I suggest you look in the File Exchange, for Image Analyst's Image Segmentation Tutorial

Syakira Akmal on 3 Apr 2017
May I know how to convert intensity of image inform of histogram?

#### 1 Comment

Image Analyst on 3 Apr 2017
[counts, grayLevels] = imhist(grayImage);

swetha Derangula on 5 Aug 2017
Edited: Walter Roberson on 5 Aug 2017
Is this code correct for entire image intensity? I didn't get any intensity value
clear all;
close all;
i=rgb2gray(o);
imshow(i)
intensityValue = i(100, 230);
meanIntensityValue = mean(mean(i));

Walter Roberson on 5 Aug 2017
No code that contains "clear all" can be correct.
intensityValue = i(100, 230);
extracts one particular pixel's intensity, and only that one pixel. However,
meanIntensityValue = mean(mean(i));
should be fine for taking the mean intensity of the entire image.
Image Analyst on 6 Aug 2017
You could also use mean2().