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intensity value of the pixel located

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Nour George
Nour George on 26 Jun 2020
Commented: Nour George on 29 Jun 2020
I have this question :
1-Read an image.
2-Show that image.
3-Write the image to the disk by new name.
4-Show additional info about image.
5-How to get the size of that image.
6-What is the intensity value of the pixel located at position(4,7)?
*I solved the previous five questions, but how can I solve the sixth question
gray = rgb2gray(image)
information = imfinfo('House.jpg')
information = information.FileSize


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Accepted Answer

Aditya Verma
Aditya Verma on 27 Jun 2020
Edited: Aditya Verma on 27 Jun 2020
Your image is stored as a matrix in MATLAB. So, for getting the pixel intensity value you need to read the image:
image_mat = rgb2gray(imread('image.jpg')); % image_mat is simply a matrix
disp(image_mat(4, 7)); % Intensity at (4,7)


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Aditya Verma
Aditya Verma on 27 Jun 2020
Hi, it was a mistake in my code. I have corrected it. It should be:
disp(image_mat(4, 7));
Aditya Verma
Aditya Verma on 27 Jun 2020
By the way, if you're new to MATLAB or programming I would recommend you to take the free MATLAB Onramp course.
Nour George
Nour George on 29 Jun 2020
The picture is colored, should I use rgb2gray()?

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More Answers (1)

Image Analyst
Image Analyst on 27 Jun 2020
Do not use image as the name of your variable. It is the name of a built-in function that you will destroy (temporarily).
The assignment did not say anything about converting to gray scale so why did you use rgb2gray()?
To get the value of a pixel, you can use impixel() or simply index it. A color image will have 3 intensities, one for each color channel.

  1 Comment

Image Analyst
Image Analyst on 27 Jun 2020
Well I'm sure you saw the code in the help for impixel:
RGB = imread('peppers.png');
% Determine the column c and row r indices of the pixels to extract.
c = [1 12 146 410];
r = [1 104 156 129];
% Return the data at the selected pixel locations.
pixels = impixel(RGB,c,r)
So I'm not sure what you're asking. Do need help in modifying that code like this?
theColor = impixel(image_mat, 7, 4);
Remember it's columns that come first, not rows. But that was so easy that I'm certain you would have been able to do that simple change of putting in 7 and 4 for the column and row and changing the name of the image variable, so I'm not really sure what you're asking.

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