App designer - problem with thresholding image

Hi folks,

I have the app attached, in which I am encountering two issues. Firstly, when trying to threshold an image and displaying the thresholded image, it would appear my function calls aren't working as the image displayed is not thresholded. (ResinThreshold function works in live editor, but not when called in app designer). The thresholding function is below.

Thanks

function ResinThreshold(app)
   imgGrey = rgb2gray(app.img);
   [counts, ~] = imhist(imgGrey, 255);
   T = otsuthresh(counts);
   BW = imbinarize(imgGrey, T);
   BW = bwareaopen(BW, 3000);
   BW = imfill(BW, 'holes');
   BW = bwperim(BW);
   BW = imdilate(BW, ones(5));
   BW = imerode(BW, ones(3));
   BW = imfill(BW, 'holes');
   app.img = app.img.*repmat(uint8(BW),[1 1 3]); 
end 

[DGM]

I don't see any attached files.

[Teshan Rezel]

hi @DGM, apologies! I thought I'd attached it...I've ammended the error!

Answer 1

[Image Analyst]

You need to display the output image

imshow(app.img);

[Teshan Rezel]

hi @Image Analyst, this is done in a seperate function call as follows:

function DisplayCrosshairs(app)
    I = imshow(app.currentImage, "Parent", app.Image); 
    app.Image.XLim = [0 I.XData(2)];
    app.Image.YLim = [0 I.YData(2)];
    
    app.Width = app.Image.XLim;
    app.Height = app.Image.YLim; 

    quarterHeight = range(app.Height)*0.125;
    halfHeight = range(app.Height)*0.5;
    threeQuarterHeight = range(app.Height)*0.875;
    quarterWidth = range(app.Width)*0.125;
    halfWidth = range(app.Width)*0.5;
    threeQuarterWidth = range(app.Width)*0.875;
    
    app.positionVector = {quarterWidth quarterHeight;halfWidth quarterHeight;threeQuarterWidth quarterHeight;quarterWidth halfHeight;halfWidth halfHeight;threeQuarterWidth halfHeight;quarterWidth threeQuarterHeight;halfWidth threeQuarterHeight;threeQuarterWidth threeQuarterHeight};
    app.checkMatrix = [app.TopLeft.Value app.TopMiddle.Value app.TopRight.Value app.CentreLeft.Value app.CentreMiddle.Value app.CentreRight.Value app.BottomLeft.Value app.BottomMiddle.Value app.BottomRight.Value];
    app.numSamplesPerImage = sum(app.checkMatrix, 1:9);   
    
    count = 0;
    
    for i = 1 : 9
        if app.checkMatrix(i) == 1
           ROI(app, app.positionVector{i,:});
           count = count + 1;
        end
    end
    
    if count == 0
       msgbox('Please select a quadrant for the crosshair to be displayed in');
    end
end

function DisplayImage(app)
    app.currentImage = fullfile(app.imageFolder(app.imageNumber).folder, app.imageFolder(app.imageNumber).name);
    app.Image.Position = [0 0 app.UIFigure.Position(3:4)];
    app.img = imread(app.currentImage);
    
    if app.ThresholdResin.Value == 1
       ResinThreshold(app); 
    end
        
    DisplayCrosshairs(app); 
    DisplayImageNumbers(app);
end

[Image Analyst]

OK but I didn't see that function called in ResinThreshold(app). Did you? Set a breakpoint in there to see if it ever gets in there.

[Teshan Rezel]

hi @Image Analyst, I've set a breakpoint and it seems to get there, and it even seems to execute the lines of code but the output just doesn't display. I've attached the mlapp file if that helps.

[Image Analyst]

I ran it but didn't know what to do. There are no instructions. You should do what I do. Have a listbox listing all the images, then a series of controls (checkboxes, pushbuttons, etc.) that say "Step 1 : select an image", "Step 2 : Select any options", "Step 3 : Mark Points", "Step 4 : Analyze selected ponts" or whatever. That will essentially guide the user through the various steps without a user manual or training. Otherwise, attach the software manual for it (though I'm not sure I'll read it if it's too lengthy).

[Teshan Rezel]

hi @Image Analyst, so the app should prompt you to select a folder with images in it on startup. once selected, pushing any of the buttons on the left of the table will move increment the relevant tally and display the next image in sequence.

I haven't listed any instructions as this is a very specific app designed for use by a very few people, and its based entirely on an existing "manual" methodology. Typically, they will go through hundreds of images on the app and tally them up, so it's not feasible to implement a listbox for images.