Convert grayscale uint8 image to RGB uint8 image

Question

I have a code to run, which uses an original image and a mask image. The code assumes that the original image is RGB, but my original image is gray scale. This must be the result of the MATLAB whos command when I run the code:

Name           Size                Bytes  Class      Attributes

mask         308x206               63448  logical              
origImg      308x206x3            190344  uint8

The mask is produced by making part of the image white and the rest is black (in a simple software like windows paint).

I want to use a gray-scale image as the origImg and produce the mask from the origImg in windows paint, but the result of the MATLAB whos command is as follows when I want to use custom photos with attributes as I said:

Name           Size                Bytes  Class    Attributes

mask         490x640x3            940800  uint8              
origImg      490x640              313600  uint8

I have to convert the origImage dimension to x3 and remove the x3 from the mask, and also convert its class from unit8 to logical. In that case, I think that the code should work properly.

What should I do here in order to prepare the origImg and mask for that goal?

origImg=imread('G:\the_path\to\my_custom\image.png');
mask=imread('G:\the_path\to\my_custom\image_mask.png');
% I have to do something here to make it work.
whos;
% Rest of the code...

Patrick Happel Patrick Happel · Accepted Answer · 2019-07-03T22:10:10

I am not sure if I understand you correctly.

To make a RGB image out of a gray-scale image, which still shows up as a gray-scale image, you can use

origImg = repmat(origImg,1,1,3);

which just repeats your gray-scale image for every channel of the RGB image.

For the mask, you have to do the opposite. since I don't know your image_mask.png file, I assume that it is a RGB image that uses only black and white. In this case, all three channels are the same and you could simply use one of them for the mask, doesn't matter which one:

mask = mask(:,:,1);

To convert it to logical, use

mask=logical(mask);

Convert grayscale uint8 image to RGB uint8 image

1 Answers