help with image processing code

Hi, i am new to matlab and need some help with this

i have used imread to read in a jpg image. however the workspace reads this as a 3 dimensional matrix, e.g. 150x100x3 uint8

how can i change this to a 2 dimensional matrix? i believe i have to use a gray scale image to accomplish this, but i cant seem to get it to work.

i have:

a = imread('image.jpg')
b = gray(a);

secondly, how can i read in a bunch of images into matlab for processing? i.e. i want to read in 1.jpg, 2.jpg, 3.jpg into the workspace. I know I need a for loop ,but i can't quite put the code together using the imread syntax.

for i = 1:5
a(i) = imread(xxxxx.jpg);
end

thank you

Answer 1

[Walter Roberson]

b = rgb2gray(a);

To read a bunch of images, please see this FAQ

[aaa]

i just have another question regarding the FAQ you have. it refers to the following code to read a bunch of jpgs in to matlab.

jpegFiles = dir('*.jpg');

numfiles = length(jpegFiles);

mydata = cell(1,numfiles);

%%Processing a sequence of files (matlab doc)

for k = 1:numfiles

mydata(k) = imread(jpegFiles(k).name);

end

my problem is that i get the error "conversion to cell from uint8 is not possible" however, the imread function makes all images into uint8, and my guess is that the above code wants a "double" format.

However, i cannot do this pre-processing if i don't have the images loaded in the first place, so it seems to be counter-intuitive. What can I do to bypass this?

[Walter Roberson]

mydata{k} = imread(jpegFiles(k).name);

Notice the {k} instead of (k)

Answer 2

[aaa]

thanks for the quick reply, i read through the faq and tried this but i get the following error

In an assignment A(:) = B, the number of elements in A and B must be the same.

Error in ==> test at 11 b(i) = sprintf('%d.jpg',k(i));

my code looks like

    for i = 1:3
        b(i) = sprintf('%d.jpg',i);
        c(i) = imread(b(i));
    end

thank you

[Image Analyst]

Try b{i} instead of b(i).