This MATLAB function reads an input MPO file and stores the image data as a MATLAB matrix. It is especially focusing on loading two (left/right-eyes) images extracted from one MPO photo file taken with FujiFilm Real W3 stereo camera and storing them separately into a MATLAB matrix. Any MPO file can be processed but have not fully tested yet.

Important note: The substantial update was applied on Oct 03 2025
The new version is optimized to be significantly faster than disk-based I/O by directly accessing the raw byte buffer of the decoded Java image object, minimizing data copies and type conversions between Java and MATLAB.

If you want to use this updated MEX routine, please copy the decode_jpeg_mex.mexw64 and jpeg62.dll files together with this imreadmpo_mex function to the same directory. You may need to compile decode_jpeg_mex.cpp by yourself depending on your environment. Importantly, even without the faster mex complied binary file, this function works using the previous 'fwrite' and 'imread' routines.

To compile decode_jpeg_mex.cpp by yourself, please follow the instructions written in the file.

function [imgs,imgsize,IFD,MPE,header]=imreadmpo(mpofile,:save_flg);     % without the mex acceleration (previous routine with fwrite and imread)
function [imgs,imgsize,IFD,MPE,header]=imreadmpo_mex(mpofile,:save_flg); % with the mex acceleration (new and faster)
(: is option)

mpofile      : input MPO-file name, a RELATIVE path format as the location  
               where this function is called is the origin
               e.g. mpofile='../DSCF0008.mpo';
save_jpg_flg : whether saving the separated left and right-eye images as separated jpg file.  
               [0|1]. 0 by defaut.

imgs         : image object, a cell strucuturr  
imgsize      : image size, [height, width]  
IFD          : MP index IDF information  
MPE          : MP entry information  
header       : header information of the input MPO file

The MPO header structure is as below  
FF E2 00 9E 4D 50 46 00 | 4D 4D 00 2A | 00 00 00 08 | 00 03 B0 00 00 07 ...  
     (APP2 marker)      |  (endian)      (offset)   |  (MP index IFD, 12 byte x N blocks) ... (image data)
                        |                           |
                        | <-- offset_start          | <-- mp_idx

imreadmpo -- A stereo photo image (*.mpo) reader. Copyright (c) 2015 Hiroshi Ban. All rights reserved.

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