Matlab: Subscript + squeeze conveniently

I'm using matlab and am quite new to it. I'm used to Java and other langauges.

Some background: I'm manipulating images, I work with the imread, imshow etc. co开发者_开发问答mmands. I want to store multiple images in an array.

So what I do is

img_list = zeroes(num_images, 1200, 1600, 3) % height,width,RGB

and then I load the images with img_list(i,:,:,:) = my_image; iteratively. That is all working fine.

Now I can display the images as I want by doing imshow(squeeze(img_list(1,:,:,:))). I can't stand this. I would like something as simple as imshow(img_list(1)).

Any idea how I can do this?

I definetly am open to change the type of img_list. Any hints is appreciated. Maybe I could do something so all my images in img_list don't have to be of the same size?

Thanks in advance. :)

The easiest solution would be to use a cell array. Each element of a cell array is a container that can hold a variable of any type and size. You access the element of a cell array as array(i) (which returns a 1-by-1 cell). To access the contents of an element of a cell array, you use curly brackets, i.e array{i}. Also have a look at CELLFUN, which allows you to perform operations on each image.

%# initialize the cell array
img_list = cell(num_images);

%# add an image to the cell array
img_list{4} = someImage;

%# display the image
imshow(img_list{4})

%# display only the red channel
imshow(img_list{4}(:,:,3))

Using cell arrays, as Jonas suggested, is probably the Right Thing -- especially if you want to be able to have images of different sizes. But it's worth mentioning that you can make the simple 4-dimensional-array approach a little nicer: make the image number the last index instead of the first. Then you can say img_list(:,:,:,i) = my_image; and imshow(img_list(:,:,:,1)); with no need for squeezing. That's probably a little better for memory locality (hence for performance) too, though it won't be any better than using cell arrays.

Define a local anonymous function:

  % Get image list from somewhere.
img_list = ...;
% ...

  % Easy-access to individual frames.
nth_image = @(k) squeeze(img_list(k,:,:,:));
image_count = size(img_list,1);

  % Loop over images.
% ...

This allows you to write the following list:

  % Process each image.
for i = 1 : image_count,
    img = nth_image(i);
    % ...
end

If you have multiple image lists or this pattern occurs often, you can write more generic functions:

function [ img ] = get_nth_image ( img_list, k )
    img = squeeze(img_list(k,:,:,:));
end
function [ img_list ] = set_nth_image ( img_list, img, k )
    img_list(k,:,:,:) = img;
end