CODEWITHSUNDEEP
matlabannotationsvideo-processing
Neil
Neil

Reputation: 287

MATLAB: How to 'color in' pixels of a grayscale image sequence?

Supposing I have the linear indices of the pixels which I would like to 'color in'.

If I wanted to set all of those pixels to some specific value in my grayscale image sequence, I could do this:

gryscl_imSeq(LinearPixIndx) = 0.7;

edit: where 'LinearPixIndx' is a p-element vector containing the linear indices of the pixels in the image sequence.

If however, I want to introduce some color, I would first need to convert my grayscale image sequence into an m x n x 3 x p matrix, which I could do like this:

RGBvideo = reshape(repmat(reshape(gryscl_imSeq,[],size(gryscl_imSeq,3)),3,1),...
         [size(gryscl_imSeq,1) size(gryscl_imSeq,2) 3 size(gryscl_imSeq,3)]);

If somebody could tell me how to convert my grayscale linear pixels indices into corresponding indices for the RGBvideo I would really appreciate it.

Or if there is a better way to go about what I'm trying to do, I would be very grateful for any suggestions.

Thanks in Advance,

N

Upvotes: 1

Views: 553

Answers (1)

A. Donda
A. Donda

Reputation: 8477

The question isn't really clear, but I guess I understand what you want. Here's one way to do it.

First I think there's a slightly more elegant way to convert from grayscale to RGB:

% determine image sequence dimensions
[m, n, N] = size(gryscl_imSeq);
% expand to RGB
rgb_imSeq = reshape(gryscl_imSeq, [m, n, 1, N]);
rgb_imSeq = repmat(rgb_imSeq, [1, 1, 3, 1]);

After that, in order to be able to apply your linear indices to all color channels and all frames, you need to explicitly linearize the pixel index by reshaping. Then you can color the pixels, and transform back into the form width x height x color channels x frames:

% linearize image dimensions
rgb_imSeq = reshape(rgb_imSeq, [m * n, 3, N]);
% color pixels
rgb_imSeq(LinearPixIndx, :, :) = repmat([1 0 0], [numel(LinearPixIndx), 1, N]);
% original shape
rgb_imSeq = reshape(rgb_imSeq, [m, n, 3, N]);

Here [1 0 0] is the RGB representation of the color you want to use, in this case red.

Upvotes: 1

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