How do I go about generating a colormap from a matlab file containing RGB values

Hi all !

I'm really stuck on a problem I would appreciate help with :

I have a matlab file containing 359 variables where each variable consists of a 360 x 3 matrix of double RGB values . For example , variable 1 looks like this :

1 1    1
1 1    1
1 1    1
1 1    1
1 0.73 1
1 0.76 1 
.
.
.
.
.

and so on until row 360 .

My question is how can I go about loading these values into a matrix from which I can generate a colormap?

I have loaded values from a structure into a matrix and represented it as a colormap pretty easily before but my issue here is that I have three RGB values for each row and I don't know how to 'combine' them to get a number which represents a color (if it is even necessary for me to do that).

Many thanks in advance !

Saba

Answer 1

[Walter Roberson]

cmap = unique(YourArray, 'rows');

or, better,

cmap = uniquetol(YourArray, 1, 'ByRows', true, 'DataScale', 0.004);

cmap is now your colormap.

[Saba Malik]

thanks - this makes sense . I'll try it out

[Saba Malik]

can i just ask why you specified data scale as 0.004 ? ?

[Walter Roberson]

0.004 is slightly less than 1/255. I was aiming to have a change of less than 1/255 be recognized as being the same color.

Answer 2

[Image Analyst]

Use the colormap() function after you've displayed your grayscale or indexed image

imshow(grayImage);
colormap(variable1); % variable1 is a 360 by 1 colormap matrix.
colorbar; % Show a colored ramp showing what intensities map to what RGB color.

[Saba Malik]

Hi - thanks for your reply

My issue is actually getting to the image stage from the values I have in the matlab file . You said 'display your grayscale image' but I wouldn't be able to do that until I generate a colormap from the RGB values in the file

[Image Analyst]

You said you have "a 360 x 3 matrix of double RGB values" - well, that is the exact format that a colormap would take. Is the matrix not a colormap? If no, then what is it?