MATLAB: How to calculate the own colormap

colormapcolorscaleMATLAB

Hi!

I want to create a new color scale that will be used for mapping to a grayscale picture.

I have three equations for RGB values calculated by linear interpolation with 256 steps scale, but I cannot find the way to calculate it on MATLAB.

Any suggestion would be greatly appreciated.

Best Answer

Make an N by 3 array. So

x = (0:255)';
redMap = your red formula.
greenMap = your green formula
blueMap = your blue formula
cMap = [redMap(:), greenMap(:), blueMap(:)];
colormap(cMap);

Related Solutions

MATLAB: How to make the own custom colormap

Step 1: Convert HEX to Decimal

>> hex = ['#f8fe34';'#f4771e';'#d94015';'#148b3e';'#085a3f';'#41332d';'#010101']
hex =
#f8fe34
#f4771e
#d94015
#148b3e
#085a3f
#41332d
#010101
>> map = sscanf(hex','#%2x%2x%2x',[3,size(hex,1)]).' / 255
map =
    0.97255      0.99608      0.20392
    0.95686      0.46667      0.11765
    0.85098      0.25098     0.082353
   0.078431       0.5451      0.24314
   0.031373      0.35294      0.24706
     0.2549          0.2      0.17647
  0.0039216    0.0039216    0.0039216
>> rgbplot(map) % to view the values

The matrix map is a standard MATLAB colormap, and it can be used anywhere that you need a colormap. You could also interpolate its values (if you need more nodes), or set this as your default colormap, or many other operations.

Step 2: Interpolate

If you want to interpolate the colormap and place the specified nodes at the given "percent" locations:

vec = [      100;       83;       68;       44;       30;       15;        0];
hex = ['#f8fe34';'#f4771e';'#d94015';'#148b3e';'#085a3f';'#41332d';'#010101'];
raw = sscanf(hex','#%2x%2x%2x',[3,size(hex,1)]).' / 255;
N = 128;
%N = size(get(gcf,'colormap'),1) % size of the current colormap
map = interp1(vec,raw,linspace(100,0,N),'pchip');

which looks like this:

MATLAB: How to create a white image

Try this to create a grayscale image:

whiteImage = 255 * ones(N, M, 'uint8');
imshow(whiteImage);

To create an RGB image, try this:

whiteImage = 255 * ones(480, 640, 3, 'uint8');
imshow(whiteImage);

Best Answer

Related Solutions

MATLAB: How to make the own custom colormap

MATLAB: How to create a white image

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