You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: calibrate_load_ext_img_Callback.m
    path of file: ./repos/PIVlab/+calibrate_NameSpace
    
    the code of the file until where you have to start completion: function calibrate_load_ext_img_Callback(~, ~, ~) %load extra calibration image
cali_folder=gui_NameSpace.gui_retr('cali_folder');
if isempty (cali_folder)==1
	if ispc==1
		cali_folder=[gui_NameSpace.gui_retr('pathname') '\'];
	else

    
function calibrate_load_ext_img_Callback(~, ~, ~) %load extra calibration image
cali_folder=gui_NameSpace.gui_retr('cali_folder');
if isempty (cali_folder)==1
	if ispc==1
		cali_folder=[gui_NameSpace.gui_retr('pathname') '\'];
	else
		cali_folder=[gui_NameSpace.gui_retr('pathname') '/'];
	end
end
try
	[filename, pathname, filterindex] = uigetfile({'*.bmp;*.tif;*.jpg;*.tiff;*.b16;','Image Files (*.bmp,*.tif,*.jpg,*.tiff,*.b16)'; '*.tif','tif'; '*.jpg','jpg'; '*.bmp','bmp'; '*.tiff','tiff';'*.b16','b16'; },'Select calibration image',cali_folder);
catch
	[filename, pathname, filterindex] = uigetfile({'*.bmp;*.tif;*.jpg;*.tiff;*.b16;','Image Files (*.bmp,*.tif,*.jpg,*.tiff,*.b16)'; '*.tif','tif'; '*.jpg','jpg'; '*.bmp','bmp';  '*.tiff','tiff';'*.b16','b16';},'Select calibration image'); %unix/mac system may cause problems, can't be checked due to lack of unix/mac systems...
end