Set a colour to a value in image processing

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Ahmed Alsaadi 2015-11-13

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关闭： MATLAB Answer Bot 2021-8-20

Map.jpg

I have a color map, which is attached, has 7 regions (A_1, A_2, A_3, B_1, B_2, C_1 and C_2). The locations of these regions are fixed on the map (x and y are constant). Also I have values (numbers) ,which represent other variables for these regions, that are

    C_2          1                   
    C_1    0.49534                   
    B_2    0.35648                   
    B_1    0.35444                   
    A_3    0.20162                   
    A_2    0.09704                   
    A_1    0.09481

I want to represent these number as colours on the map. Let's say C_2 is the highest so it can be represented in red colour while C_1 should be represented by another colour depending on its value and so on so forth. These numbers can change from run to another and that should be represented on the map as changes in the colours only not locations.

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Ahmed Alsaadi 2015-11-13

Any help is appreciated

Image Analyst 2015-11-13

Would you like some help? I'm not sure.

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Answer 1

Image Analyst 2015-11-13

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Just create a colormap with 8 colors - the 7 you want plus white for "the background". Then apply it.

C_2 =    1
C_1 =   0.49534
B_2 =   0.35648
B_1 =   0.35444
A_3 =   0.20162
A_2 =   0.09704
A_1 =   0.09481
indexedImage(1:30,1:30) = C_2;
indexedImage(1:30,31:60) = C_1;
indexedImage(1:30,61:90) = B_2;
indexedImage(31:60,1:30) = B_1;
indexedImage(31:60,31:60) = C_2;
indexedImage(31:60,61:90) = A_3;
indexedImage(61:90,1:30) = A_2;
indexedImage(61:90,31:60) = A_1;
imshow(indexedImage, [], 'InitialMagnification', 800);
axis on;
colormap(jet(256));
colorbar;

Your numbers are not equally spaced and so some have very similar colors. You might have to do precision surgery on your colormap to make it how you like, but honestly, it might be better to just create an RGB image with known colors.

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Ahmed Alsaadi 2015-11-13

Each run has its own values(only values in the array will change, that are A_1, A_2, A_3, ... and C_2, after each run), then ONLY colours of C_1, C_2, etc on the map should be changed since the colours should be combined with the values.While C_1, C_2, etc must stay in the same location.

I would rather to have different colours for different areas I used red colour as an example to refer to the max value, if we comeback to the same example above which is

C_2 = 1 (red) C_1 = 0.49534 (Yellow) B_2 = 0.35648 (Blue) B_1 = 0.35444 (Magenta) A_3 = 0.20162 (Cyan) A_2 = 0.09704 (Green) A_1 = 0.09481 (Black)

As we can see in the example above C_2 should be represented in a red colour on the map and C_1 should be yellow, so on so forth.

BUT

In the next run A_1 might be the max value so it is going to be red and it should be represented in the red colour on the map and the same for the rest of the array.

In all cases my image is divided into sections that are A_1, A_2 .... C_2. These must be fixed in their places unless I won't be able to recognise which section is which