how to read an imagecaptured by webcam

%webcamlist
cam = webcam('Integrated Webcam');
preview(cam);
closePreview(cam)
img = snapshot(cam);
imshow(img)
%image(img)
clear('cam');
    
I = imread(img);

srcFiles1 = dir('C:\b\*.bmp');    
for j = 1 : length(srcFiles1)
    filename1 = strcat('C:\b\',srcFiles1(j).name);
    I2 = imread(filename1);
    points = detectSURFFeatures(I);
    length(points)
    points2 = detectSURFFeatures(I2);
    length(points2)
    [features1, validPoints1] = extractFeatures(I, points);
    [features2, validPoints2] = extractFeatures(I2, points2);
    indexPairs = matchFeatures(features1, features2);
    matchedPoints1 = validPoints1(indexPairs(:, 1), :);
    matchedPoints2 = validPoints2(indexPairs(:, 2), :);
    showMatchedFeatures(I, I2, matchedPoints1, matchedPoints2, 'montage');
    figure;
end   
%end

 output:
Error using imread>parse_inputs (line 450)
The file name or URL argument must be a character vector.
Error in imread (line 322)
[filename, fmt_s, extraArgs, was_cached_fmt_used] = parse_inputs(cached_fmt, varargin{:});
Error in acquire (line 13)
[X, map] = imread(img);

Error using imread>parse_inputs (line 450)
The file name or URL argument must be a character vector.

Error in imread (line 322)
[filename, fmt_s, extraArgs, was_cached_fmt_used] = parse_inputs(cached_fmt, varargin{:});

Error in acquire (line 13)
[X, map] = imread(img);

i have captured an image using webcam and then am trying to compare this image with the images in the database.why is matlab unable to read image file?

Answer 1

[Cris LaPierre]

I think the issue here is that img is not a file, but a matrix of pixel values already. You therefore don't need to use imread to read it. It's already been 'read' in.

Try just using I=img;

[venus tyagi]

It is working now.But the images have to be converted to gray format.the following error is coming when the acquired and the compared image are converted to gray.

Error in acquire (line 20)

I2 = rgb2gray(imread(filename1));

[Cris LaPierre]

Please share the entire error message. Would be nice to also include a sample image that produces this error.