show an image as categorised

I have an image with 3 layers (R,G,B). I want to show each layer as a cateogorised image as I can define the range of values in each category. I also want to add a legend as it show the range of values and the assigned color, a map scale (in kilometer) and geographical north direction. for eaxample I want to show the layer 1 as: 0.05-0.1>>blue 0.1-0.15>>green 0.15-0.2>>yellow 0.2-0.25>>red

Could you please help me about that?

Answer 1

[Walter Roberson]

Perhaps you could use contour() and supply the level list

[Hassan]

thanks Walter for the comment. I think contour() show the pixels with the same value as a line which is different with what I want.

[Walter Roberson]

To turn off the lines in contour(), pass the additional parameter 'none' as the linespec argument.

[Hassan]

I used contour(Myimg(:,:,1),'none') but it gave me an error message (?? Error using ==> contour at 73

Error in color/linetype argument.).

[Walter Roberson]

It appears that 'none' is a later version than you or I are using. But you can use this:

[edges,chandle] = contourf(Myimg(:,:,1));

set(chandle,'LineStyle','none');

[Hassan]

thanks Walter. Well, it seems the image was rotated after using this command. and I don't know how to add a legend, a map scale and the geographical north. I don't know in the resulted image each color means.

[Walter Roberson]

[edges,chandle] = contourf(Myimg(:,:,1).', [0.1, 0.15, 0.2, 0.25]);

set(chandle,'LineStyle','none');

colorbar;

colormap([0 0 1; 0 1 0; 1 1 0; 1 0 0]);

annotation('arrow', [X1 X2],[Y1 Y2], 'HeadStyle', 'hypocycloid'); %with appropriate X and Y

I do not know if there is a good way to create a map scale with tick marks.

[Hassan]

thanks Walter for the code. It still doesnn't show the image in the right position as it rotated the image again.It seems it doesnt show all the pixels.

[Walter Roberson]

Which direction does using Myimg(:,:,1) display relative to what you would like displayed?

[Hassan]

well in the array I want to have each pixel displayed according to its row and column.

Answer 2

[Sean de Wolski]

Perhaps you could convert it to be identical to a label image and then use label2rgb to show it?

[Hassan]

thanks Sean. I think label2rgb() is more useful for a classfied image while my image is not. I want to assign one color to a range of pixel values.

[Sean de Wolski]

Yes. So set every pixel in each range to an integer monotonically increasing from 1. label2rgb sounds like exactly what you want!

[Hassan]

I know if I use L = bwlabel(BW, n), it gave me a matrix with identical values. But I don't know how to tell the function to assign the identical value to a range of values.

[Sean de Wolski]

Use hist on each channel reshaped to a vector; get the second output (the bin); reshape all three channels back into their beginning shape; set up some criteria on which bins make what values and then label based on the values.

Show us a better set of sample data and the expected results. Perhaps a 2x2x3 matrix and the criteria used to determine "category"

[Hassan]

a(:,:,1) =

0.1000 0

0.0050 0.5000

a(:,:,2) =

0.1500 0.0500

0.0550 0.5500

a(:,:,3) =

0.2000 0

0.0100 1.0000

for example in the array a, I want to have 3 category like:

a(:,:,1):

0.001 to 0.005>>blue

0.006 to 0.1>>green

0.1 to 0.5>> yellow

for a(:,:,2):

0.01 to 0.05>>blue

0.06 to 0.15>>green

0.16 to 0.55>> red

and so on

[Hassan]

sorry Sean, I didnt underestand what I should do.