How to read and store pixel intensity and coordinates values of a grayscale-converted image?

I have a colormap image and I convert it to gray scale using:

A=imread('Image1.jpg')
B=rgb2gray(A)

Now I want to be able to know the pixel intensities of each pixel as a function of their coordinates, or basically just stored with their coordinates such that later I can scan pixel intensities through a desired coordinate range.

I know impixel(B, xi, yi) will give me the pixel intensity that I want at (xi, yi), but where are all these single pixel intensity values are stored? And also impixel() command gives me 3 pixel intensity values, which are all the same, even though the image is grayscale, is there a way to get the single pixel intensity value of the grayscale image?

Thanks,

Answer 1

[Divya Gaddipati]

Hi,

As I understand, you want to get the pixel intensity value of the grayscale image (B) at a particular location (xi, yi).

You can directly use the matrix row-column indexing method to get the pixel intensity value at a particular location. For example, modifying your code as follows:

A = imread('Image1.jpg') 
B = rgb2gray(A) 
intensity_value = B(xi, yi); 
% xi, yi is the location at which you want to get the intenisty value

The “impixel” function, which you used returns the intensity value as an RGB triplet. Hence, for a grayscale image, R, G and B values obtained will be equal. For more information on how to use “impixel”, you can refer to the following documentation:

https://www.mathworks.com/help/images/ref/impixel.html

[YOGITAA YOGITAA]

how to get intensity in a matrix of each location of pixel?

[yanqi liu]

each location of pixel

row : y

col: x

then we cant get pixel by B(y, x)

[Image Analyst]

@YOGITAA YOGITAA I don't even know what that means. In DIvya's code A IS the color of each pixel, and B IS the "intensity" of each pixel (after the color image has been converted to gray scale). So explain why A and B are not what you want. What do you want that is different than that?

To get the intensity of a single pixel, you can specify the y (row) location first and then the x (column) location, unlike what Divya did, so you'd do

intensity_value = B(yi, xi)