How to read images with positive integer? No imead()

I want to import images into matlab workspace, they should contain positive integers and zeros. If I use imread(), they will be all zeros.

[Image Analyst]

Why? What kind of integers are they? I doubt they will be all zeros with imread(). Please attach your image.

[Geoff Hayes]

Wenyi - can you attach one of these images so that we can take a look at it? Or describe the images - what type are they? What is the integer type (8-bit, 16-bit, etc.)?

[Wenyi Xiao]

Here are pictures.

I have 1500 pictures like these.

Answer 1

[Catalytic]

I definitely don't get all zeros with imread. Problem solved?

>> nnz(imread('C0039_100122_INDS.png'))

ans =

        4624

>> nnz(imread('C0039_101785_INDS.png'))

ans =

       12177

[Wenyi Xiao]

I store image data like this.

Each matrix contains data of one of the images.

However, when I look the data, they are all zeros.

[Wenyi Xiao]

images_data = cell(1500,1);
for S = 1:size(want_files,1)
    images_data{S,1} = imread(pngFile_names{want_files(S,1),1}); %load image data from 1500 matched files
end

this is the code I used.

[Wenyi Xiao]

I found the positive integers, Thank you!