MATLAB script that splits an image into blocks/tiles.

Split_Image.m

clf;
Image = imread("peppers.png");
[Image_Height,Image_Width,Number_Of_Colour_Channels] = size(Image);

Block_Size = 50;
Number_Of_Blocks_Vertically = ceil(Image_Height/Block_Size);
Number_Of_Blocks_Horizontally = ceil(Image_Width/Block_Size);
Image_Blocks = struct('Blocks',[]);

Index = 1;
for Row = 1: +Block_Size: Number_Of_Blocks_Vertically*Block_Size
    for Column = 1: +Block_Size: Number_Of_Blocks_Horizontally*Block_Size
        
    Row_End = Row + Block_Size - 1;
    Column_End = Column + Block_Size - 1;
        
    if Row_End > Image_Height
       Row_End = Image_Height;
    end
    
    if Column_End > Image_Width
       Column_End = Image_Width;
    end
    
    Temporary_Tile = Image(Row:Row_End,Column:Column_End,:);
    
    %Storing blocks/tiles in structure for later use%
    Image_Blocks(Index).Blocks = Temporary_Tile;
    subplot(Number_Of_Blocks_Vertically,Number_Of_Blocks_Horizontally,Index); imshow(Temporary_Tile);
    Index = Index + 1;
    
    end  
end

%***************************************************%
%Uncomment to save the images to seperate .jpg files%
%***************************************************%
% for Block_Index = 1: length(Image_Blocks)
%     imwrite(Image_Blocks(Block_Index).Blocks,"Block" + num2str(Block_Index) + ".jpg"); 
% end

Split_Image_And_Reconstruct.m

clf;
Image = imread("peppers.png");
[Image_Height,Image_Width,Number_Of_Colour_Channels] = size(Image);

Block_Size = 50;
Number_Of_Blocks_Vertically = ceil(Image_Height/Block_Size);
Number_Of_Blocks_Horizontally = ceil(Image_Width/Block_Size);
Image_Blocks = struct('Blocks',[]);

Index = 1;
for Row = 1: +Block_Size: Number_Of_Blocks_Vertically*Block_Size
    for Column = 1: +Block_Size: Number_Of_Blocks_Horizontally*Block_Size
        
    Row_End = Row + Block_Size - 1;
    Column_End = Column + Block_Size - 1;
        
    if Row_End > Image_Height
       Row_End = Image_Height;
    end
    
    if Column_End > Image_Width
       Column_End = Image_Width;
    end
    
    Temporary_Tile = Image(Row:Row_End,Column:Column_End,:);
    
    %Storing blocks/tiles in structure for later use%
    Image_Blocks(Index).Blocks = Temporary_Tile;
%     subplot(Number_Of_Blocks_Vertically,Number_Of_Blocks_Horizontally,Index); imshow(Temporary_Tile);
    Index = Index + 1;
    
    end  
end

%*************************************************************************%
%MODIFYING THE BLOCKS%
%*************************************************************************%

for Block_Index = 1: length(Image_Blocks)
    if(mod(Block_Index,2) == 0)
        %Darkening every other block%
        Image_Blocks(Block_Index).Blocks = 0.5.*(Image_Blocks(Block_Index).Blocks);
    end
end

%*************************************************************************%
%RECONSTRUCTING THE IMAGE%
%*************************************************************************%

Reconstructed_Image = zeros(size(Image));

Block_Index = 1; 
for Row = 1: +Block_Size: Image_Height
    for Column = 1: +Block_Size: Image_Width
        
        Height_Of_Block = size(Image_Blocks(Block_Index).Blocks,1);
        Width_Of_Block = size(Image_Blocks(Block_Index).Blocks,2);
        Reconstructed_Image(Row:Row+Height_Of_Block-1,Column:Column+Width_Of_Block-1,:) = Image_Blocks(Block_Index).Blocks;
        Block_Index = Block_Index + 1;

    end  
end

imshow(uint8(Reconstructed_Image));

Split_Image_Truncated.m

clf;
Image = imread("peppers.png");
[Image_Height,Image_Width,Number_Of_Colour_Channels] = size(Image);

Block_Size = 50;
Number_Of_Blocks_Vertically = floor(Image_Height/Block_Size);
Number_Of_Blocks_Horizontally = floor(Image_Width/Block_Size);
Image_Blocks = struct('Blocks',[]);

Index = 1;
for Row = 1: +Block_Size: Number_Of_Blocks_Vertically*Block_Size
    for Column = 1: +Block_Size: Number_Of_Blocks_Horizontally*Block_Size
        
    Row_End = Row + Block_Size - 1;
    Column_End = Column + Block_Size - 1;
        
    if Row_End > Image_Height
       Row_End = Image_Height;
    end
    
    if Column_End > Image_Width
       Column_End = Image_Width;
    end
    
    Temporary_Tile = Image(Row:Row_End,Column:Column_End,:);
    
    %Storing blocks/tiles in structure for later use%
    Image_Blocks(Index).Blocks = Temporary_Tile;
    subplot(Number_Of_Blocks_Vertically,Number_Of_Blocks_Horizontally,Index); imshow(Temporary_Tile);
    Index = Index + 1;
    
    end  
end

%***************************************************%
%Uncomment to save the images to seperate .jpg files%
%***************************************************%
% for Block_Index = 1: length(Image_Blocks)
%     imwrite(Image_Blocks(Block_Index).Blocks,"Block" + num2str(Block_Index) + ".jpg"); 
% end

Splitting_Multiple_Images.m

%Getting all the images in the directory%
Folder_Directory = "";
File_Type = "png";
Images = dir(fullfile(Folder_Directory,"*." + File_Type));

for Image_Index = 1: length(Images)
    Image_Name = Images(Image_Index).name;
    Image = imread(fullfile(Folder_Directory,Image_Name));
    File_Prefix = strsplit(Image_Name,".");
    File_Prefix = File_Prefix{1};
    [Image_Height,Image_Width,Number_Of_Colour_Channels] = size(Image);

    Block_Size = 100;
    Number_Of_Blocks_Vertically = floor(Image_Height/Block_Size);
    Number_Of_Blocks_Horizontally = floor(Image_Width/Block_Size);
    Image_Blocks = struct('Blocks',[]);
    Index = 1;
    for Row = 1: +Block_Size: Number_Of_Blocks_Vertically*Block_Size
        for Column = 1: +Block_Size: Number_Of_Blocks_Horizontally*Block_Size

        Row_End = Row + Block_Size - 1;
        Column_End = Column + Block_Size - 1;

        if Row_End > Image_Height
           Row_End = Image_Height;
        end

        if Column_End > Image_Width
           Column_End = Image_Width;
        end

        Temporary_Tile = Image(Row:Row_End,Column:Column_End,:);

        %Storing blocks/tiles in structure for later use%
        Image_Blocks(Index).Blocks = Temporary_Tile;
%         subplot(Number_Of_Blocks_Vertically,Number_Of_Blocks_Horizontally,Index); imshow(Temporary_Tile);
        Index = Index + 1;

        end  
    end

    mkdir(File_Prefix + "_Blocked/");
    for Block_Index = 1: length(Image_Blocks)
        imwrite(Image_Blocks(Block_Index).Blocks,fullfile(File_Prefix + "_Blocked/",File_Prefix + "_" + num2str(Block_Index) + ".jpg")); 
    end
end

Output Results Preview

Hello, can you tell me how to fix this error while I want to save the splitting blocks? Thank you in advance.

In TA1 (line 158)
Error using imwrite>parse_inputs (line 523)
A filename must be supplied.

Error in imwrite (line 418)
[data, map, filename, format, paramPairs] = parse_inputs(varargin{:});

Error in TA1 (line 160)
imwrite(Image_Blocks(Block_Index).Blocks,fullfile(File_Prefix + "_Blocked/",File_Prefix +
"BlockDivision" + num2str(Block_Index) + ".png"));

@febbyftrp Any chance you could attach the full code. I can’t seem to find anything in this code snippet that would cause issues.

Hi Febby As it can be shown from the error in the screen ,you have problem with your file directory ,show it again and make it sure that you write the true directory file name,here is the link about imwrite error in Matlab ; I think below link is the solution for this problem ; https://www.mathworks.com/matlabcentral/answers/1563336-how-to-solve-error-a-filename-must-be-supplied-in-imwrite Dehar369 -GitHub

…

On Sun, 12 Dec 2021, 22:33 Michael, ***@***.***> wrote: ***@***.**** commented on this gist. ------------------------------ @febbyftrp <https://github.com/febbyftrp> Any chance you could attach the full code. I can’t seem to find anything in this code snippet that would case issues. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <https://gist.github.com/71eaab442ece262ebd5dfe326ba0c9b7#gistcomment-3992835>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ATIMP4YKMKLXERP5IGF5ORLUQUILLANCNFSM4Z72RTZA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

@MichaelTr7 Here is my full code to split the blocks, I copy it from your github sir. Thank you so much for the help sir.

%Splitting the frames into 8x8 blocks
Folder_Directory = '/Users/febbyfitri/Documents/MATLAB/febby/AVI(Uncompressed)_subtraction';
File_Type = "png";
Images = natsortfiles(dir(fullfile(Folder_Directory,"*." + File_Type)));
for Image_Index = 1
    Image_Name = Images(Image_Index).name;
    Image = imread(fullfile(Folder_Directory,Image_Name));
    File_Prefix = strsplit(Image_Name,".");
    File_Prefix = File_Prefix{1};
    [Image_Height,Image_Width,Number_Of_Colour_Channels] = size(Image);

    % The first way to divide an image up into blocks is by using mat2cell()
    Block_SizeC = 240; %Columns in block.
    Block_SizeR = 135; % Rows in block.
    Number_Of_Blocks_Vertically = floor(Image_Height/Block_SizeR);
    Number_Of_Blocks_Horizontally = floor(Image_Width/Block_SizeC);
    Image_Blocks = struct('Blocks',[]);
    Index = 1;
    for Row = 1: +Block_SizeR: Number_Of_Blocks_Vertically*Block_SizeR
        for Column = 1: +Block_SizeC: Number_Of_Blocks_Horizontally*Block_SizeC

        Row_End = Row + Block_SizeR - 1;
        Column_End = Column + Block_SizeC - 1;

        if Row_End > Image_Height
           Row_End = Image_Height;
        end

        if Column_End > Image_Width
           Column_End = Image_Width;
        end

     
        Temporary_Tile = Image(Row:Row_End,Column:Column_End,:);
        %Storing blocks/tiles in structure for later use%
        Image_Blocks(Index).Blocks = Temporary_Tile;
        subplot(Number_Of_Blocks_Vertically,Number_Of_Blocks_Horizontally,Index); 
        imshow(Temporary_Tile);
        Index = Index + 1;
        end  
    end
    
    mkdir(File_Prefix + "_Blocked/");
    for Block_Index = 1: length(Image_Blocks)
        imwrite(Image_Blocks(Block_Index).Blocks,fullfile(File_Prefix + "_Blocked/",File_Prefix + "BlockDivision" + num2str(Block_Index) + ".png")); 
    end
end

@febbyftrp I believe that the path must be added since this is an absolute path that MATLAB does not have access to. Relative paths in the MATLAB Current Folder side panel do not have to be added. To add your folder the following code can be added to the top of your script:

Folder_Directory = '/Users/febbyfitri/Documents/MATLAB/febby/AVI(Uncompressed)_subtraction';
addpath(Folder_Directory);

I have already tried it sir, but still can't work. Does the version of Matlab affect sir? btw, I use Matlab 2018a @MichaelTr7

@febbyftrp I don’t believe the version of MATLAB should have any effect on this. Is it possible to just load an image from that directory/folder using the imread() function?

Use the Split_Image_And_Reconstruct.m to modify and reconstruct the image blocks.