How to make colormaps like the attached colorbar?

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hello community,
I am quite new to colorbar interpolation techniques. Therefore, I would really appreciate your help in this regards.
I want to make a colormaps like the attached colorbar.
thanks in advance.
  2 Comments
Subhodh Sharma
Subhodh Sharma on 20 Nov 2021
@DGM thanks for your response. I want the same color gradient with same colors in the colorbar. only same
colors.
I don't want borderless. I want to make a contour plot. But I can't seem to find any colormap which matches with the above one.
So, I want to make a colormap like the above one with same colors and gradient.

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Accepted Answer

DGM
DGM on 20 Nov 2021
Edited: DGM on 20 Nov 2021
If you just want the colormap used in that image, this is it.
A = imread('colorbarimage.png');
np = 37; % number of points
x0 = 75; % centerline of bar
y0 = 181; % location of first breakpoint
yf = 767; % location of last breakpoint
dy = (yf-y0)/(np-2);
x = x0*ones(1,np);
y = y0-dy/2:dy:y0-dy+np*dy;
imshow(A); hold on; % show image
plot(x,y,'kx','linewidth',2) % and sample locations
% extract a colortable from the image
ct = im2double(squeeze(A(round(y),x0,:)))
ct = 37×3
0.8000 0.4510 0.4510 0.8588 0.4627 0.4627 0.9137 0.4784 0.4784 0.9686 0.4902 0.4902 1.0000 0.5216 0.5020 1.0000 0.5804 0.5020 1.0000 0.6392 0.5020 1.0000 0.6980 0.5020 1.0000 0.7569 0.5020 1.0000 0.8118 0.5020
If you want the colortable to be longer, then you can interpolate.
ctlong = interp1(1:np,ct,linspace(1,np,256))
ctlong = 256×3
0.8000 0.4510 0.4510 0.8083 0.4526 0.4526 0.8166 0.4543 0.4543 0.8249 0.4560 0.4560 0.8332 0.4576 0.4576 0.8415 0.4593 0.4593 0.8498 0.4609 0.4609 0.8581 0.4626 0.4626 0.8659 0.4648 0.4648 0.8737 0.4670 0.4670
  1 Comment
Subhodh Sharma
Subhodh Sharma on 20 Nov 2021
@DGM Many thanks to you. It's exactly I was looking for. Can' thank you enough!

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More Answers (1)

KSSV
KSSV on 20 Nov 2021
Edited: KSSV on 20 Nov 2021
Pick the RGB values of maximum value color you want and pick the RGB values of minimum value color you want to represent.
Let the values be:
r0 = rand ;g0 = rand ; b0 = rand ;
r1 = rand ;g1 = rand ; b1 = rand ;
M1 = [r1 g1 b1] ; % RGB valaues of color which represents maximum value
M0 = [r0 g0 b0] ; % RGB valaues of color which represents minimum value
N = 12 ; % say you want to have 64 colors/ variations between maximum and minimum
cmap = [linspace(r1,r0,N)' linspace(g1,g0,N)' linspace(b1,b0,N)'] ;
Z = peaks(100) ;
pcolor(Z)
colormap(cmap)
shading interp
colorbar

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