How to convert multiple .png files to .mat files

Question

spatial data (.png)

001.png
002.png
003.png
.
.
.
00n.png

to

001.mat
002.mat
003.mat
.
.
.
00n.mat

Answer 1

Complementing the answer of EitanT, if you have files which does not have such filename restrictions, such as:

file01.png
file02.png
fls1.png
fls2.png
pics001.png
pics002.png

You can use dir function, which gives you more flexibility. For example:

filenames = dir('*.png'); %# get information of all .png files in work dir
n  = numel(filenames);    %# number of .png files

for i = 1:n
    A = imread( filenames(i).name );

    %# gets full path, filename radical and extension
    [fpath radical ext] = fileparts( filenames(i).name ); 

    save([radical '.mat'], 'A');                          
end

fileparts is a MATLAB function which decomposes the filename in file path, radical and extension. E.g., if I have the file /home/user/photo.png, this function will return:

fpath   = /home/user
radical = photo
ext     = .png

File format error

OP got the following error:

??? Error using ==> imread at 387 Unable to determine the file format. Error in ==> PNG2MATFiles at 5 A = imread( filenames(i).name );

I've download his original *.png images and tested them with file linux command. My output:

FY2E_2011_09_01_00_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_01_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_02_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_03_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_04_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_05_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_06_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_07_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_08_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_09_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100 FY2E_2011_09_01_10_01_ir1_proj.png: Matlab v5 mat-file (little endian) version 0x0100

imread can't open these files as 'png' because they are already stored as .mat.

Answer 2

Try this:

for i = 1:n
    A = imread(['00', num2str(i), '.png'], 'png');  %# Read PNG file
    save(['00', num2str(i), '.mat'], 'A');          %# Store data to MAT file
end