assigning values in color bar

Hello,

I currently have an image that ranges from 0-1 and is in grayscale. I then assign the image to a new colormap which produces the desired colormap of 0-1. This part works well, however, for the next step I would like to reassign the colorbar to show values from 17-27 instead of 0-1, as the 0-1 represents 17-27*C. Is there a way I can reassign the values on the colorbar to show the 17-27 instead of 0-1?

Thanks for the help!

I = im2double(Image);
I2 = I(:,:,1);

colormap('jet');
x = linspace(0,100,640);
y = linspace(100,0,640);
z = I(:,:,3);
zmin = min((min(z)));
zmax = max((max(z)));
surf(x,y,z,'EdgeColor','none')
view(0,90)
colorbar

Answer 1

[DGM]

Why not just scale it appropriately instead of trying to fake it? Don't need to use surf either.

% you have a single-channel image that's within unit-scale
I = im2double(imread('cameraman.tif'));

% rescale it such that 0,1 correspond to 17 and 27
inrange = [0 1];
outrange = [17 27];
Irescaled = rescale(I,outrange(1),outrange(2), ...
    'inputmin',inrange(1),'inputmax',inrange(2));

% display it
imagesc([0 100],[100 0],Irescaled);
set(gca,'ydir','normal')
colormap('jet');
colorbar

Note that I'm mapping 0 and 1 to [17 27]. I'm not mapping the data extrema to [17 27].

Answer 2

[Voss]

min_val = 17;
max_val = 27;

N = max_val-min_val+1;
t = linspace(0,1,N);              % tick locations    (0, 0.1, 0.2, ..., 1)
tl = linspace(min_val,max_val,N); % tick label values (17, 18, 19, ..., 27)

colorbar('Ticks',t,'TickLabels',tl);

[Voss]

Example:

% some image data:
Image = randi([0 255],640,640,3,'uint8');

% your code
I = im2double(Image);
I2 = I(:,:,1);
colormap('jet');
x = linspace(0,100,640);
y = linspace(100,0,640);
z = I(:,:,3);
zmin = min((min(z)));
zmax = max((max(z)));
surf(x,y,z,'EdgeColor','none')
view(0,90)

% my suggestion:
min_val = 17;
max_val = 27;

N = max_val-min_val+1;
t = linspace(0,1,N);              % tick locations    (0, 0.1, 0.2, ..., 1)
tl = linspace(min_val,max_val,N); % tick label values (17, 18, 19, ..., 27)

cb = colorbar('Ticks',t,'TickLabels',tl);

% add a colorbar label too:
cb.Label.String = '°C';
cb.Label.Rotation = 0;