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Retrieve Image Data Types

This example shows how to retrieve images from a Microsoft® Access™ database. To run this example, define the function parsebinary using this code.

function [x,map] = parsebinary(o,f)
%PARSEBINARY Write binary object to disk and display if image.
%   [X,MAP] = PARSEBINARY(O,F) writes the binary object in O to disk
%   in the format specified by F. If the object is an image, 
%   display the image. This file was released for demonstration
%   purposes only. A Microsoft(R) Access(TM) database contains image data. 
%   Use an ODBC driver to read the data. This function writes 
%   any temporary files to the current working directory.
%
%   Valid file formats are:
%
%   BMP     Bitmap
%   DOC     Microsoft(R) Word document
%   GIF     GIF file
%   PPT     Microsoft(R) Powerpoint(R) file
%   TIF     TIF file
%   XLS     Microsoft(R) Excel(R) spreadsheet
%   PNG     Portable Network Graphics

% Transform object into vector of data
v = java.util.Vector;
v.addElement(o);
bdata = v.elementAt(0);

% Open file to write data to disk
fid = fopen(['testfile.' lower(f)],'wb');

% n specifies the end point of data written to disk
n = length(bdata);

% File type determines how many bytes of header data that
% the ODBC driver prepended to the data.

switch lower(f)
    
    case 'bmp'
      m = 79;
      
    case 'doc'
      m = 86;
      
    case 'gif'
      m = 5722;
      
    case 'png'
       
      m = 182;
      n = length(bdata)-285;
      
    case 'ppt'
      m = 94;
     
    case 'tif'  
      m = 6472;
      
    case 'xls'
      m = 83;
    
    otherwise
      error(message('database:parsebinary:unknownFormat'))
      
end

% Write data to disk
fwrite(fid,bdata(m:n),'int8');
fclose(fid);

% Display if image
switch lower(f)
   
  case {'bmp','tif','gif','png'}

    [x,map] = imread(['testfile.' lower(f)]);
    imagesc(x)
    colormap(map)
    
  case {'doc','xls','ppt'}
      
    % Microsoft(R) Office formats  
    % Insert path to Microsoft(R) Word or Microsoft(R) Excel(R) 
    % executable here to run from MATLAB(R) prompt.
    % For example: 
    % !d:\msoffice\winword testfile.doc
end
  1. Connect to the Microsoft Access data source using the ODBC driver. The database contains the table Invoice.

    conn = database('datasource','','');
    
  2. Import the InvoiceNumber and Receipt columns of data from Invoice.

    sqlquery = 'SELECT InvoiceNumber,Receipt FROM Invoice';
    results = fetch(conn,sqlquery);
    
  3. View the imported data.

    results
    ans = 
    
      10×2 table
    
        InvoiceNumber         Receipt     
        _____________    _________________
    
             2101        [1948410×1 uint8]
             3546        [2059994×1 uint8]
            33116        [ 487034×1 uint8]
            34155        [2059994×1 uint8]
            34267        [2454554×1 uint8]
            37197        [1926362×1 uint8]
            37281        [2403674×1 uint8]
            41011        [1920474×1 uint8]
            61178        [2378330×1 uint8]
            62145        [ 492314×1 uint8]
    
  4. Assign the image element you want to the variable receipt.

    receipt = results.Receipt{1};
    
  5. Run the parsebinary function. The function writes retrieved data to a file, strips ODBC header information from it, and displays receipt as a bitmap image in a figure window. Ensure that your current folder is writable so that the parsebinary function can write the output data.

    cd 'I:\MATLABFiles\myfiles'
    parsebinary(receipt,'BMP');
    

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