Struct to double conversion

I have 59 images in a file and when i am running it, it shows "59x1 struct" but i need to convert it into double format which i need it. Can anyone please help me to do that.

[ES]

Running what?

[Stephen23]

The MATLAB documentation explains how to access data in a structure:

https://www.mathworks.com/help/matlab/matlab_prog/access-multiple-elements-of-a-nonscalar-struct-array.html

[Tousif Ahmed]

Running the code, myDir = 'face/'; ext_img= '*.jpg'; x = dir([myDir ext_img]); The images are in the face folder from which i am accessing. When i am running the above code, the images are stored in x with 59 images and looks like this. x= 59x1 struct. I need to change it to double format. Hope you are understanding the question

[Stephen23]

Images are usually 3D arrays. You have 59 of them. You want them merged into one 4D array? What is the problem with accessing them in the structure? The data is already there.

[Tousif Ahmed]

I need to use the neural network and i am taking these 59 images as training images, so while training i am getting error. The images should be in double format as i am using the default "Wine Classification".

[Stephen23]

If this is your code:

 x = dir([myDir ext_img]);

then x does not contain image data at all, but is a structure of file information. I wold suggest that you start by actually doing some reading about dir (which does not load image data at all, as you will find out when you read its documentation).

Then you should search this forum for importing images in a loop. You will find many useful threads, e.g.:

https://www.mathworks.com/matlabcentral/answers/57446-faq-how-can-i-process-a-sequence-of-files

[Tousif Ahmed]

if you know how to read the 59 images in double format, it will be of great help to me

[Stephen23]

@Tousif Ahmed: I already gave you a link that explains exactly how to import images in a loop, and shows example code too. Did you read the link that I gave you?

[Tousif Ahmed]

Yes i saw the link,jpeg files in struct but for the neural network i need in double.

[Stephen23]

I know that you want a double array. But you have not answered my question about the dimensions that you want the double array to have. I will ask once more:

The images are (most likely) 3D. How many dimensions do you want the double array to have? Or, put another way, how do you want the images arranged relative to one-another?

[Tousif Ahmed]

i want training images to be in this 3x178.. like this are you asking?

Answer 1

[Saurabh]

To convert a struct of 59 images to a double format, you will need to loop over each image and convert it by calling the im2double() function. Here's some sample code:

% Assuming your struct of images is called "images"
num_images = length(images);
double_images = cell(1,num_images);
for i = 1:num_images
    double_images{i} = im2double(images(i).data);
end

Answer 2

[Parag Jhunjhunwala]

There are 2 ways of converting an image to double format:

1. Using im2double() function:

    double_images=[];
    for i=1:length(images)
        img = imread(images{i}); % read the image
        double_images(i) = im2double(img); % convert the image to double
    end

2. Using double() function:

    double_images=[];
    for i=1:length(images)
        img = imread(images{i}); % read the image
        double_images(i) = double(img); % convert the image to double
    end

Both of these methods convert an image to a double-precision array, but the main difference is that im2double() function scales the output range to [0,1] while double() function keeps the original dynamic range of the input image.