Converting JPG images into a cell arrays

Hi

I have the following code i want to convert images jpg (TrainingData) into cell arrays ,where each cell containing a 28-by-28 matrix representing a synthetic image of fingerprint

dataDir= fullfile('Data/');
exts = {'.jpg','.png','.tif','BMP'};
 
 
imds = imageDatastore(fullfile(dataDir),...
'IncludeSubfolders',true,'FileExtensions','.jpg','LabelSource','foldernames');
countEachLabel(imds);
 
[TrainData, TestData] = splitEachLabel(imds, 0.5);
size(TrainData);
countEachLabel(TrainData);

for i = 1:numImages
    img = readimage(TrainData, i); 
    
    img  = imbinarize(img); 
      
    
end 

Answer 1

[Walter Roberson]

sz = size(img);
RB = 28; CB = 28;
NRB = floor(sz(1)/RB);
LOR = sz(1) - NRB*RB;
NCB = floor(sz(2)/CB);
LOC = sz(2) - NCB*CB;
if LOR ~= 0
  rbs = [RB * ones(1,NRB), LOR];
else
    rbs = RB * ones(1,NRC);
end
if LOC ~= 0
    cbs = [CB * ones(1,NCB), LOC];
else
    cbs = CB * ones(1,NCB);
end

tiles = mat2cell(img, rbs, cbs, size(img,3));

See also mat2tiles in the File Exchange

And watch out for the titles that are not 28 x 28. This code does not assume that the image is an exact integer multiple of 28 in each direction, and it does not throw away any partial blocks.

[Abdussalam Elhanashi]

Hi Walter Roberson

I tried the code but i got error

dataDir= fullfile('Data/');
exts = {'.jpg','.png','.tif','BMP'};
 
 
imds = imageDatastore(fullfile(dataDir),...
'IncludeSubfolders',true,'FileExtensions','.jpg','LabelSource','foldernames');
countEachLabel(imds);
 
[TrainData, TestData] = splitEachLabel(imds, 0.5);
size(TrainData);
countEachLabel(TrainData);
numImages = numel(TrainData.Files); 

for i = 1:numImages
    img = readimage(TrainData, i); 
    
    img  = imbinarize(img); 
     sz = size(img);
RB = 28; CB = 28;
NRB = floor(sz(1)/RB);
LOR = RB - NRB*RB;
NCB = floor(sz(2)/CB);
LOC = CB - NCB*CB;
if LOR ~= 0
  rbs = [RB * ones(1,NRB), LOR];
else
    rbs = RB * ones(1,NRC);
end
if LOC ~= 0
    cbs = [CB * ones(1,NCB), LOC];
else
    cbs = CB * ones(1,NCB);
end
tiles = mat2cell(img, rbs, cbs, size(img,3)); 
    
end 


Error

Error using mat2cell (line 89)
Input arguments, D1 through D3, must sum to each dimension of the input matrix size, [200  200    3].

Error in Untitled (line 34)
tiles = mat2cell(img, rbs, cbs, size(img,3));

[Walter Roberson]

You are right, I had a bug in the code. I fixed it above.

Caution: your 400 x 400 image will end up with partial tiles. On each dimension, you have 14 full groups of 28, and then you have partial group of 8 to reach 400. Because of this, some of the blocks in tiles will be 8 x 28, and some will be 28 x 8, and one of them will be 8 x 8.