Colormap appears darker on another plot, how to change that ?

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Gronaz 2021-6-13

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https://ww2.mathworks.cn/matlabcentral/answers/855270-colormap-appears-darker-on-another-plot-how-to-change-that

编辑： LO 2021-6-17

I am plotting states of a solution at different times, and to visualise the solution I added a colormap that depends on the x position. I also superposed a sphere to help visualise the 3D plot. I should note that in order to color the plots, I used the patch function. Unfortunately, the 3D plot appears much darker than the energy plot (see the figures). I put two figures to show that the colormap still had some influence on the 3D plot the parameters for the plot of the sphere are :

'FaceColor' = [0.99, 0.99, 0.99];
alpha  0.07;

The two figures (at no point I can see colors as bright as at x=0 on the 3D-plot) :

Thank you for your time !

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Answer 1

LO 2021-6-13

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https://ww2.mathworks.cn/matlabcentral/answers/855270-colormap-appears-darker-on-another-plot-how-to-change-that#answer_723920

编辑：LO 2021-6-13

在 MATLAB Online 中打开

you could change the colormap of your plot/s by adding (or subtracting) fixed values according to your needs

k = 0.01; % factor by which you want to increase color value
cmap = colormap; % actual colormap
size_cm=size(cmap); % get the size of the map
new_map = cmap + repelem(k,size_cm(1),size_cm(2)); % calculate the new colormap
new_map(new_map>1)=1; % make sure values do not exceed the max of 1
colormap(<subplot_handle>,new_map) % apply new map

here is my test code

clc
k = 0.02; % darker color, if you put 0 you have the default, negative values will darken the map
cmap = colormap;
size_cm=size(cmap);
new_map = cmap + repelem(k,size_cm(1),size_cm(2))
new_map(new_map>1)=1; % this makes sure there is no value higher than 1
new_map(new_map<0)=0; % this makes sure there is no value lower  than 0
ax1=subplot(2,1,1)
surf(randi(50,50),'edgecolor','none')
colormap(ax1,new_map)
view(2)
ylim([0 50])
axis tight equal
k = 0.7; % brighter color, if you put 1 you have the max
cmap = colormap;
size_cm=size(cmap);
new_map = cmap + repelem(k,size_cm(1),size_cm(2))
new_map(new_map>1)=1; % this makes sure there is no value higher than 1
new_map(new_map<0)=0; % this makes sure there is no value lower  than 0
ax2=subplot(2,1,2)
surf(randi(50,50),'edgecolor','none')
colormap(ax2,new_map)
view(2)
ylim([0 50])
axis tight equal

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Gronaz 2021-6-17

Sorry for the late reply, and thank you for your reply !

For the test case you showed, it works nicely, although I don't get how I could link a colorbar with both colormaps (in some cases I would like to have a colorbar linked to all subplots), and I also have to set k manually so that the colors appear at the same brightness on both plots.

LO 2021-6-17

编辑：LO 2021-6-17

在 MATLAB Online 中打开

sadly that needs to be set manually for each plot but using some work around (if you just used the command colorbar this will change all colorbars in your figure). I do not remember it but somewhere in the MATLAB forum I am sure you'll find it. Maybe see here.

What worked for me sometimes was this (example using scatter plots of different colors):

color2 = flipud(cool(length( array_data1  ) ) );
color1 = hot(length( array_data2 ) );
hold on
scatter(array_data1(:,1),array_data1(:,2),1,'filled','CData', color1)
scatter(array_data2(:,1),array_data2(:,2),1,'filled','CData', color2)

In this example I am using part of 2 colormaps (hot and cool) based on the length of the data arrays to be plotted. One color vector is flipped as I wanted to have the first datapoints to be darker in both cases. The last data points of my 2 arrays are lighter in color. I guess this could work for any plot accepting CData property.

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