how to assign certain range of pixel values with desired color for classification of image?

Question

sowjanya 2020-2-16

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https://ww2.mathworks.cn/matlabcentral/answers/505750-how-to-assign-certain-range-of-pixel-values-with-desired-color-for-classification-of-image

编辑： Rik 2020-2-18

I used GLCM to obtain properties of image. I have displayed different properties taking effects on input image .

for a start, I have taken energy image ..now i am trying to classify the image using thresholding method.

the water body in my image can be detected and i noted the minimum and maximum pixelvalue of that region using image viewer app in matlab

i wanted to assign blue color to that specific range of pixel values. i have written sample code how i want to classify

how many changes i try to make also ,somehow it is either displaying as water body (only) in grey scale or the entire image is returning into blue

clc;
clear all;
close all;
Image=imread('D:/project/myfeatures/energystack.tif');
blue(:,:,3)=zeros(size(Image));
for i=1:size(Image,1)
   for j=1:size(Image,2)
        pixel=Image(i,j);
        if (pixel>= 40&&pixel<= 140)
           blue(:,:,3)=Image;
        end
   end
end
figure
imshow(blue(:,:,3))

any type of suggestion or guidance is welcome.thank you!

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Answer 1

Image Analyst 2020-2-16

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Try imoverlay() to overlay your segmented/masked image over your original.

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Answer 2

Rik 2020-2-16

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编辑：Rik 2020-2-18

在 MATLAB Online 中打开

What you need to do is replicate your grayscale image to three channels to make it an RGB image. Then you can modify the the color for your specific pixels.

%get an example image
defimage = pow2(get(0,'DefaultImageCData'),47);
IM = bitshift(defimage,-37);IM = fix(IM);
IM = bitand(IM,31);IM = IM/max(IM(:));
I=uint8(255*IM);
L=I<100;
I(L)=0;
I=repmat(I,1,1,3);
[ind1,ind2]=find(L);
ind3=3*ones(size(ind1));
ind=sub2ind(size(I),ind1,ind2,ind3);
I(ind)=255;
%an alternative is to extend the logical mask to 3D:
%L3D=L;L3D(1,1,3)=0;L3D=L3D(:,:,[3 2 1]);
%I(L3D)=255;
figure(1),clf(1)
subplot(1,3,1)
imshow(IM),title('original image')
subplot(1,3,2)
imshow(L),title('mask')
subplot(1,3,3)
imshow(I),title('modified image')

And as Image Analyst suggests below: all code from I(L)=0; until the figure creation can be replaced by this:

I=imoverlay(I,L,[0 0 1]);

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sowjanya 2020-2-18

在 MATLAB Online 中打开

what exactly below line mean ?

I(L,3)=1;

Rik 2020-2-18

L is a 2D logical, so that line sets the third channel (the blue channel) to 1 on every position where L is true. You may need to use 255 instead of 1 by the way.

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