Using MATLAB for median, quartil, interquartil span and resolution - matlab

Question

I have a picture in MATLAB and decompositioned it to R, G and B channel.
And now I need to figure out resolution, median, upper and lower quartil, interquartil span and modus.
Here is the code I use for it:
close all; clc; clear all
I = imread('image_S006_I0000.jpg');
imshow(I)
[R S T] = size(I);
Red(:,:,1)=I(:,:,1);
Red(:,:,2)=zeros(R,S);
Red(:,:,3)=zeros(R,S);
Green(:,:,1)=zeros(R,S);
Green(:,:,2)=I(:,:,1);
Green(:,:,3)=zeros(R,S);
Blue(:,:,1)=zeros(R,S);
Blue(:,:,2)=zeros(R,S);
Blue(:,:,3)=I(:,:,1);
OR
Red=double(I(:,:,1));
Red=zeros(R,S);
Red=zeros(R,S);
Green=zeros(R,S);
Green=double(I(:,:,1));
Green=zeros(R,S);
Blue=zeros(R,S);
Blue=zeros(R,S);
Blue=double(I(:,:,1));
OR
Red(:,:,1)=double(I(:,:,1));
Green(:,:,1)=double(I(:,:,1));
Blue(:,:,1)=double(I(:,:,1));
cat(3, uint8(Red), zeros(R, S), zeros(R, S));
others = zeros(R, S);
red_plt = cat(3, uint8(Red), others, others);
green_plt = cat(3, others, uint8(Green), others);
blue_plt = cat(3, others, others, uint8(Blue));
figure()
subplot(131);imshow(red_plt)
subplot(132);imshow(green_plt)
subplot(133);imshow(blue_plt)
NOW PLOTTITG (It doesn't print it in Red, Green and Blue color. First two
are just all black, the third one is black and white):
figure()
subplot(131);imshow(uint8(Red))
subplot(132);imshow(uint8(Green))
subplot(133);imshow(uint8(Blue))
[x1 y1 z1] = size(I);
% MEDIAN.
imgmedianR = median (Red(:))
imgmedianG = median (Green(:))
imgmedianB = median (Blue(:))
%QUARTIL
r025 = quantile(Red,0.25)
r075 = quantile(Red,0.75)
g025 = quantile(Green,0.25)
g075 = quantile(Green,0.75)
b025 = quantile(Blue,0.25)
b075 = quantile(Blue,0.75)
%INTERQUARTIL SPAN
r_iqr = iqr(Red)
g_iqr = iqr(Green)
b_iqr = iqr(Blue)
modus_Red = mode(Red(:))
modus_Green = mode(Green(:))
modus_Blue = mode(Blue(:))
MEDIAN: When I try to count MEDIAN, it gives me a bunch of numbers (actually matlab prints out a number for each column separately).
What have I done wrong there?
QUARTIL: The same problem as I have in code for MEDIAN. What have I done wrong there?
INTERQUARTIL SPAN: Matlab prints out subsequent error:
Mixed integer class inputs are not supported.
What have I done wrong?
RESOLUTION: I need to find out a resolution of the image using Matlab. I have tried out funciton imfinfo, but the info isn't included. How can I find such an information using any kind of Matlab function?
Thank you very much in advance!

Answer 1

You save every separate colour in a 3d matrix. This is not nessecary. So save them in a 2d matrix as follows:
Red=double(I(:,:,1));
Green=double(I(:,:,2));
Blue=double(I(:,:,3));
Note there is a conversion to double. That's needed for the iqr. Also use in every function Red(:) instead of Red (same for other colours of course). If you change all that, it should work just fine.
Concerning the resolution, that is just the number of pixels for the height and the width, in your case R and S.
ps you're calling size(I) twice.
In case of plotting the red, green and blue separately, you need to make the same matrix as the original, with exception that only 1 colour is non-zero. The image is a RxSx3 matrix. So if you want to plot the red part you need to make an RxSx3 matrix where only red is non-zero:
cat(3, uint8(Red), zeros(R, S), zeros(R, S));
So in total it should look like this
others = zeros(R, S);
red_plt = cat(3, uint8(Red), others, others);
green_plt = cat(3, others, uint8(Green), others);
blue_plt = cat(3, others, others, uint8(Blue));
figure()
subplot(131);imshow(red_plt)
subplot(132);imshow(green_plt)
subplot(133);imshow(blue_plt)
EDIT:
The whole code:
I = imread('image_S006_I0000.jpg');
imshow(I)
[R S T] = size(I);
Red=double(I(:,:,1));
Green=double(I(:,:,2));
Blue=double(I(:,:,3));
others = zeros(R, S);
red_plt = cat(3, uint8(Red), others, others);
green_plt = cat(3, others, uint8(Green), others);
blue_plt = cat(3, others, others, uint8(Blue));
figure()
subplot(131);imshow(red_plt)
subplot(132);imshow(green_plt)
subplot(133);imshow(blue_plt)
% MEDIAN.
imgmedianR = median (Red(:))
imgmedianG = median (Green(:))
imgmedianB = median (Blue(:))
%QUARTIL
r025 = quantile(Red(:),0.25)
r075 = quantile(Red(:),0.75)
g025 = quantile(Green(:),0.25)
g075 = quantile(Green(:),0.75)
b025 = quantile(Blue(:),0.25)
b075 = quantile(Blue(:),0.75)
%INTERQUARTIL SPAN
r_iqr = iqr(Red(:))
g_iqr = iqr(Green(:))
b_iqr = iqr(Blue(:))
modus_Red = mode(Red(:))
modus_Green = mode(Green(:))
modus_Blue = mode(Blue(:))