Problem on gray scale image.

Hi. i used gray = rgb2gray(I) at command window but why can't i get a grayscale image? thank you!

Answer 1

[Walter Roberson]

grayscaleimage = rgb2gray(I);
image(grayscaleimage);
colormap(gray);

Please note that "gray" is a MATLAB function for constructing grayscale colormaps. Writing to a variable named "gray" interferes with using the function "gray".

Answer 2

[Esther]

thanks for answer. i did this tutorial, http://www.mathworks.com/videos/developing-algorithms-with-matlab-68914.html just that i used a color image instead of a gray image. but i couldn't get a grayscale.

[Walter Roberson]

The one line of code you show above would only convert the image and write it into the variable "gray" and would not display the image at all, and would not use a correct colormap in the display.

Please show us some code in which you can reproduce the problem.

[Image Analyst]

Are you saying that you read the image using imread() into an array, and then you passed that image into rgb2gray() as Walter advised, and that you got an rgb image back out? I find that very surprising as I've never ever experienced that failure.

rgbImage = imread(filename);
grayImage = rgb2gray(rgbImage);
[rows columns numberOfColorChannels] = size(rgbImage)
[rows2 columns2 numberOfColorChannels2] = size(grayImage)

Run that code on your image and tell me what shows up in the command window. Please upload your original rgb image (which would be a BMP, TIFF, JPG, or PNG file, not a .fig file, and not a screenshot), and your code so I can verify before I submit a bug report.

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/7924-where-can-i-upload-images-and-files-for-use-on-matlab-answers

[Esther]

rows =

        1936

columns =

        2592

numberOfColorChannels =

     3

rows2 =

        1936

columns2 =

        2592

numberOfColorChannels2 =

     1

[Walter Roberson]

Okay, and then what do you do with grayImage to display it?

[Image Analyst]

So you DID get a gray scale image. Why did you say you did not?