SIFT features extraction from images and send it to CNN or other classifiers

Question

baby 2022-3-3

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1662475-sift-features-extraction-from-images-and-send-it-to-cnn-or-other-classifiers

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Good day,

I have been strugling for days with the following code:

imds = imageDatastore('mydata','IncludeSubfolders',true,'LabelSource','foldernames');
numImages = numel(imds.Files);
for i = 1:numImages
img = readimage(imds,i); img = im2gray(img);
img = imbinarize(img); % points = detectSIFTFeatures(img);
hogFeatures(i, :) = extractHOGFeatures(img,'CellSize',cellSize);
end

........... The above code is part of MATLAB help, and works well for my data that contains arabic alphabets one per image. (sample attached).

. I have little code to convert these features to an .csv file from a code of SVM classifier or a CNN reads features from the .csv file and does the classification.

When I want to do the same for SIFT features, instead of HOG, the code becomes as:

----------------

imds = imageDatastore('mydata','IncludeSubfolders',true,'LabelSource','foldernames');
numImages = numel(imds.Files);
for i = 1:20
img = readimage(imds,i); img = im2gray(img);
img = imbinarize(img); points = detectSIFTFeatures(img);
SiftFeatures (i, :) = extractFeatures(img,locations);
end

.................................line 6 generates and error that this type of indexing is not allowed in this type of objects.I can see the SiftFeatures object has complex nested list of variables (7 varibales ) of different dimensions and their inner dimension vary with every images.

my questions are:

How to convert this data in a feature vector to save it as .csv file or any other suitable form a CNN can read it.
What features I must take (scale, orentation, octave ..... etc) for better classififcation, or I need to pick all of them.

thanks in advance.

Shahid B.