Color Label Image By Region Property

I have a binarized image with multiple identified regions that each have a particular orientation. I would like to color the identified regions (similar to label2rgb) where the color is related to a given region's property (in this case orientation). For example, I'd want the orientation to map from (-90, 90) onto a HSV colormap. Is there a way to do this?

Answer 1

[Walter Roberson]

discretize the orientation angle into an integer, uint8() that, then ind2rgb

Answer 2

[Image Analyst]

You can still use label2rgb -- just construct your colormap so that each row has the color you want for that particular blob (based on it's orientation)

help label2rgb

 LABEL2RGB Convert label matrix to RGB image.
    RGB = LABEL2RGB(L) converts a label or a categorical matrix L, into a
    color RGB image for the purpose of visualizing the labeled regions.
 
    RGB = LABEL2RGB(L, MAP) defines the colormap to be used in the RGB
    image.  MAP can either be an n x 3 colormap matrix, a string or a
    character vector containing the name of a colormap function (such as
    'jet' or 'gray'), or a function handle of a colormap function (such as
    @jet or @gray). LABEL2RGB evaluates MAP so that there is a different
    color for each region in L. If MAP is not specified, 'jet' is used as
    the default.
 
    RGB = LABEL2RGB(L, MAP, ZEROCOLOR) defines the RGB color of the
    elements labeled 0  or <undefined> in the input label matrix L.
    ZEROCOLOR can either be an RGB triple, or one of the following: 'y'
    (yellow), 'm', (magenta), 'c' (cyan), 'r'(red), 'g' (green), 'b'
    (blue), 'w' (white), or 'k' (black). If ZEROCOLOR is not specified, [1
    1 1] is used as the default.
    
    RGB = LABEL2RGB(L, MAP, ZEROCOLOR, ORDER), controls how colormap colors
    are assigned to regions in the label matrix.  If ORDER is 'noshuffle'
    (the default), then colormap colors are assigned to the label matrix
    regions in numerical order.  If ORDER is 'shuffle', then colormap
    colors are pseudorandomly shuffled.
 
    RGB = LABEL2RGB(...,Name,Value) specifies additional name-value pair
    arguments described below:
 
    'OutputFormat'   Specify the output format. Valid values are:
                      
                     'image'      The output is an M-by-N-by-3 image
                                  where M-by-N is the size of the input
                                  label matrix.
 
                     'triplets'   The output is an M-by-3 matrix where
                                  each row is an 1-by-3 RGB triplet and
                                  M is the number of elements in the
                                  input label matrix.
 
                                  Specify this value when you want to
                                  convert a list of labels into a list
                                  of RGB colors.
 
                     Default: 'image'
 
    Class Support
    -------------
    The input label matrix L can be numeric or categorical. When L is
    numeric, it must contain finite nonnegative integers. RGB is uint8.
 
    Example 1
    ---------
    %Use label2rgb to customize display of label matrix.
 
        I = imread('rice.png');
        figure, imshow(I)
        BW = imbinarize(I);
        CC = bwconncomp(BW);
        L = labelmatrix(CC);
        RGB = label2rgb(L);
        RGB2 = label2rgb(L, 'spring', 'c', 'shuffle');
        figure, imshow(RGB), figure, imshow(RGB2)
 
    Example 2
    ---------
    %Use label2rgb to display categorical label matrix.
 
        load('buildingPixelLabeled','label');
        RGB = label2rgb(label);
        figure, imshow(RGB)
 
    See also BWCONNCOMP,BWLABEL,COLORMAP,ISMEMBER,LABELMATRIX,WATERSHED.

    Documentation for label2rgb
       doc label2rgb