How to perform automatic conversion of matrix dimensions of images in a way that it works for both rgb and grayscale ??

1 次查看（过去 30 天）

Jack 2013-2-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/63575-how-to-perform-automatic-conversion-of-matrix-dimensions-of-images-in-a-way-that-it-works-for-both-r

评论： Jan 2017-11-9

To perform face recognition, i have a train database with some images. The images in train database need to be pre-processed before they are used for comparison with the test image, which is the input image.

This is what i have done :

    T = [];
    for i = 1 : Train_Number
    str = int2str(i);
    str = strcat('\',str,'.jpg');
    str = strcat(TrainDatabasePath,str);
    img = imread(str);
    img = rgb2gray(img);
    img = imresize(img, [200 180]);
    [irow icol] = size(img);    
    temp = reshape(img',irow*icol,1);  
    % temp = reshape(permute(double(img), [2,1,3]), irow*icol, 1);
    T = [T temp]; % 'T' grows after each turn                    
    end

This works fine when the train database contains only rgb images. But for grayscale images, it gives error related to dimensions.

How can i make it work for both rgb and grayscale ??

2 个评论
显示无隐藏无

Jan 2013-2-15

Please do not only claim, that there is an error, but post the message and mention the line also. The less we have to guess, the more efficient is an answer. Thanks.

Jack 2013-2-15

编辑：Jack 2013-2-15

在 MATLAB Online 中打开

Ok.. When i include a grayscale image in the database, i get an error.

This is my code :

    T = [];
    for i = 1 : Train_Number
    str = int2str(i);
    str = strcat('\',str,'.jpg');
    str = strcat(TrainDatabasePath,str);
    img = imread(str);
%   img = rgb2gray(img);
    img = imresize(img, [200 180]);
    [irow icol] = size(img);    
    temp = reshape(permute(double(img), [2,1,3]), irow*icol, 1);
    T = [T temp]; % 'T' grows after each turn   
    end

This is the error i get :

*??? Error using ==> horzcat

CAT arguments dimensions are not consistent.

Error in ==> CreateDatabase at 50

T = [T temp]; % 'T' grows after each turn*

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Jan 2013-2-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/63575-how-to-perform-automatic-conversion-of-matrix-dimensions-of-images-in-a-way-that-it-works-for-both-r#answer_75166

编辑：Jan 2013-2-15

在 MATLAB Online 中打开

Some cleanup and an implicit conversion of grayscale images to pseudo-RGB:

    nCol = 200;
    nRow = 180;
    % BUG?! T    = nan(nCol * nRow, Train_Number);  % Pre-allocate!!!
    T    = nan(nCol * nRow * 3, Train_Number);  % Pre-allocate!!! [EDITED]
    for i = 1 : Train_Number
       filename = fullfile(TrainDatabasePath, sprintf('%d.jpg', i));
       img = imread(filename);
       if ndims(img) == 2                       % Gray scale image:
          img = double(cat(3, img, img, img));  % Pseudo RGB image
       end
       img = imresize(img, [nCol, nRow]);
       temp = permute(img, [2,1,3]);
       T(:, i) = temp(:);
    end

But, I do not expect that the training of a face recognition system is efficient, when you feed it with RGB and gray-scale images. I'd prefer converting the RGB to gray scale instead.

img = rgb2gray(img);

8 个评论
显示 6更早的评论隐藏 6更早的评论

Mahima Goyen 2017-11-9

Matrix dimensions must agree.

Error in recog (line 18) Difference = double(InImage)-m; % Centered test image

Error in main (line 115) OutputName=recog(TestImage,m,A,Eigenfaces);

HELP????

Jan 2017-11-9

@Mahima Goyen: All you provide is a line of code and the partial error message. It seems like "double(InImage)" and "m" do not have the same dimensions. Without further information, there is no chance to guess, why this happens or what the problem is.

Please open a new thread for a new question and add more information.

请先登录，再进行评论。