How to make colormaps like the attached colorbar?

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.

[DGM]

In what aspects?

Do you want it to be borderless?

Do you want it to be shaped the same?

Do you just want the same colors?

[Subhodh Sharma]

@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.

Answer 1

[DGM]

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

[Subhodh Sharma]

@DGM Many thanks to you. It's exactly I was looking for. Can' thank you enough!

Answer 2

[KSSV]

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

[Subhodh Sharma]

@KSSV thanks to you..