Matlab, AppDesigner-Convert image on a good type and use it in "imread" function - arrays

Question

I use AppDesigner inMATLAB to show photos with changed RGB. But there is the problem with character of the photo.
When I switch on my own fuction "changeRGB", finally "choosenImage" has 20bytes, class "char" and size(1x10). OK!
There is no problem in using the "function OpenButtonValueChanged". OK!
There is the problem with "function UploadButtonPushed". OK!
ABOUT THE PROBLEM:
When I click button which callback is "function UploadButtonPushed" I get the error:
"Error using imread>parse_inputs (line 502)
The file name or URL argument must be a character
vector or string scalar."
"Error in imread (line 342)
[source, fmt_s, extraArgs, was_cached_fmt_used] =
parse_inputs(cached_fmt, varargin{:});"
WHY?
Because in the "function UploadButtonPushed" my choosenImage has 1977624bytes, class "uint8" and size(681x968x3). So it's too bug for "imread".
WHAT I TRIED:
When in "function OpenButtonValueChanged" I convert a photo, adding "char": (myimage = char(app.clickedImage)); the class of the photo is changing from uint8 to char but the size.
When I use "num2cell", the claas of the photo is changing on "cell" but size and number of bytes are the same- so big. And I get the Error: "Error using imread>parse_inputs (line 502) The file name or URL argument must be a character vector or string scalar."
In my own function "changeRGB" I used "imread(image)" and here is the problem with the size of the photo. Do you know how to get the correct one?
%my own properties in AppDesigner- to use them in different functions
properties (Access = public)
clickedImage;
addR = 1;
addG = 1;
addB = 1;
end
%first function in AppDeesigner
function OpenButtonValueChanged(app, event)
value = app.OpenButton.Value;
[file, howManyFiles] = chooseImagesFromComputer; %myown function
%I load 3 images which are showed as miniatures
myFile1 = imread(file{1});
imshow(myFile1, 'Parent', app.UIAxes1_1);
myFile2 = imread(file{2});
imshow(myFile2, 'Parent', app.UIAxes1_2);
myFile3 = imread(file{3});
imshow(myFile3, 'Parent', app.UIAxes1_3);
%take values of changed RGB from the slider
app.addR = app.SliderR.Value
app.addG = app.SliderG.Value
app.addB = app.SliderB.Value
%work only on one image to change its colors. app.clickedImage, app.addR, app.addG, app.addB are properties at the beginning of the code
app.clickedImage = file{1};
app.clickedImage = changeRGB(app.clickedImage,app.addR,app.addG,app.addB); %changeRGB- my own function- here is the problem. I add it bottom
imshow(app.clickedImage,'Parent',app.UIAxesMain);
end
%second function in AppDesigner
%here is the button to upload color of the photo
function UploadButtonPushed(app, event)
myimage = app.clickedImage;
myimage = changeRGB(myimage,app.addR,app.addG,app.addB);
imshow(myimage);
end
%here is my own function in matlab, not in AppDesigner, which makes problem:
function [changedImage] = changeRGB(choosenImage, addR, addG, addB)
whos
loadedImage = imread(choosenImage);
R = loadedImage(:,:,1); %extract one of the color channels
G = loadedImage(:,:,2);
B = loadedImage(:,:,3);
RBG = cat(3,R,G,B);
R_adj2 = R + addR;
G_adj2 = G + addG;
B_adj2 = B + addB;
changedImage = cat(3,R_adj2,G_adj2,B_adj2);
end

Answer 1

First, you make unnecessary operations in changeRGB
function [changedImage] = changeRGB(choosenImage, addR, addG, addB)
loadedImage = imread(choosenImage);
loadedImage = bsxfun(#sum, loadedImage, reshape([addR, addG, addB], [1 1 3]);
end
Then this function return an array (the modified image) so in UploadButtonPushed(app, event) when you run myimage = app.clickedImage;, you are passing the modified array instead of the image path, that you set here app.clickedImage = changeRGB(app.clickedImage,app.addR,app.addG,app.addB);
So you have to change the design of your variables, because app.clickedImage is saving either the image path, or the image itself. Consider having 2 different variables.
A good advice also is to use matlab debugger which is really good help to find the source of this kind of problems.