Detect Anomalies in Pills During Live Image Acquisition

Download Pretrained Network

This example uses a pretrained network that is trained to detect pill anomalies. Download this network.

trainedPillAnomalyDetectorNet_url = ...
    "https://ssd.mathworks.com/supportfiles/vision/data/trainedFCDDPillAnomalyDetectorSpkg.zip";
downloadTrainedNetwork(trainedPillAnomalyDetectorNet_url,pwd); 
net = load(fullfile(pwd,"folderForSupportFilesInceptionModel","trainedPillFCDDNet.mat"));
detector = net.detector;

Prepare Data Set for Calibration and Testing

You use a pretrained pill anomaly detector because the images used to train it are similar to the images captured and classified in this example. Rather than retrain the existing model from scratch, you capture images for calibration and testing. If your workflow requires a visual inspection model for a different application, refer to Detect Image Anomalies Using Explainable FCDD Network (Computer Vision Toolbox) for more information on how to train the model from scratch.

Set Up Image Acquisition Hardware

Connect to your camera using the videoinput function and specify its properties. This example uses the OS generic video interface to acquire images from a Logitech® webcam with the YUV2_352x288 video format.

vid = videoinput("winvideo","1","YUY2_352x288");
vid.ReturnedColorSpace = 'rgb';
vid.FramesPerTrigger = 70;

Get the source properties of the videoinput object. Specify device-specific properties to adjust for optimal image data collection. The values you specify for these properties depend on the camera hardware and the surrounding environment that images are being captured in.

src = getselectedsource(vid);

Acquire Data

After setting up and configuring your image acquisition hardware, you can collect images. Collect data in immediate acquisition mode. For more information about trigger types, see Specifying the Trigger Type.

start(vid);
wait(vid);

After you finish capturing images, save the acquired image frames to MATLAB workspace and save the frames as TIF files using imwrite.

img = getdata(vid,70);

for f=1:vid.FramesAcquired
     imwrite(img(:,:,:,f), "image"+f+".tif");
end

delete(vid);

In the current working directory create a folder titled ImageData. Within this folder create two new folders titled normal and dirt, then move images of normal and anomalous pills, respectively, into these folders.

The original data set used in this example contained 40 normal images and 30 dirt images.

These two images show an example from each class. A normal pill with no defects is on the left and a pill contaminated with dirt is on the right. The properties of these images align closely with the properties of the training data set from the Detect Image Anomalies Using Explainable FCDD Network (Computer Vision Toolbox) example.

Load and Preprocess Data

Create an imageDataStore object, imds, to manage the collection of image files from both normal and dirt image classes.

imageDir = fullfile(pwd,"ImageData");
imds = imageDatastore(imageDir,IncludeSubfolders=true,LabelSource="foldernames");

Split imds into calibration and testing sets (imdsCal and imdsTest, respectively). The images for calibration are used to determine a threshold value for the classifier. The classifier labels images with anomaly scores above the threshold as anomalous. The remaining images are for testing and are used to evaluate the classifier.

normalTrainRatio  = 0;
anomalyTrainRatio = 0;
normalCalRatio  = 0.70;
anomalyCalRatio = 0.60;
normalTestRatio  = 1 - (normalTrainRatio + normalCalRatio);
anomalyTestRatio = 1 - (anomalyTrainRatio + anomalyCalRatio);

rng(0);
[imdsTrain,imdsCal,imdsTest] = splitAnomalyData(imds,["dirt"],...
    NormalLabelsRatio=[normalTrainRatio normalCalRatio normalTestRatio],...
    AnomalyLabelsRatio=[anomalyTrainRatio anomalyCalRatio anomalyTestRatio]);

Splitting anomaly dataset
-------------------------
* Finalizing... Done.
* Number of files and proportions per class in all the datasets:

                          Input                      Train                   Validation                    Test       
              NumFiles          Ratio          NumFiles    Ratio    NumFiles          Ratio          NumFiles    Ratio
              _____________________________    _________________    _____________________________    _________________

    dirt         30       0.428571428571429       0          0         18       0.391304347826087       12        0.5 
    normal       40       0.571428571428571       0          0         28       0.608695652173913       12        0.5 

Add binary labels to normal and dirt images in both calibration and test data sets by using the transform function with the operations specified by the addLabelData helper function.

dsCal = transform(imdsCal,@addLabelData,IncludeInfo=true);
dsTest = transform(imdsTest,@addLabelData,IncludeInfo=true);

Visualize a sample of calibration data that contains both normal and anomalous images.

numObs = length(imdsCal.Labels);
idx = randperm(numObs,9);
montage(imdsCal,Indices=idx)

Calibrate and Test Classification Model

Select Anomaly Threshold

Use the calibration data set to select an anomaly score threshold for the anomaly detector. The detector classifies images based on whether their scores are above or below the threshold value. You use both normal and anomalous images to determine the threshold.

Get the mean anomaly score and ground truth label for each image in the calibration set and plot a histogram of scores.

scores = predict(detector,dsCal);
labels = imdsCal.Labels ~= "normal";

numBins = 20;
[~,edges] = histcounts(scores,numBins);
figure
hold on
hNormal = histogram(scores(labels==0),edges);
hAnomaly = histogram(scores(labels==1),edges);
hold off
legend([hNormal,hAnomaly],"Normal","Anomaly")
xlabel("Mean Anomaly Score")
ylabel("Counts")

Calculate the optimal anomaly threshold using the anomalyThreshold (Computer Vision Toolbox) function. Specify the first two input arguments as the ground truth labels, labels, and predicted anomaly scores, scores, for the calibration data set. Specify the third input argument as true because true positive anomalous images have a labels value of true.

thresh = anomalyThreshold(labels,scores,true);

Set the Threshold property of the anomaly detector to the optimal value.

detector.Threshold = thresh;

Evaluate Classification Model

Classify each image in the test set as either normal or anomalous using the anomaly detector, detector.

testSetOutputLabels = classify(detector,dsTest);

Get the ground truth labels of each test image.

testSetTargetLabels = dsTest.UnderlyingDatastores{1}.Labels;

Evaluate the anomaly detector by calculating performance metrics by using the evaluateAnomalyDetection (Computer Vision Toolbox) function. The function calculates several metrics that evaluate the accuracy, precision, sensitivity, and specificity of the detector for the test data set.

metrics = evaluateAnomalyDetection(testSetOutputLabels,testSetTargetLabels,"dirt");  

Evaluating anomaly detection results
------------------------------------
* Finalizing... Done.
* Data set metrics:

    GlobalAccuracy    MeanAccuracy    Precision    Recall    Specificity    F1Score    FalsePositiveRate    FalseNegativeRate
    ______________    ____________    _________    ______    ___________    _______    _________________    _________________

          1                1              1          1            1            1               0                    0        

The ConfusionMatrix property of metrics contains the confusion matrix for the test set. Extract the confusion matrix and display a confusion plot. The recalibrated classification model with the anomaly threshold selected produces very few false positives and false negatives.

M = metrics.ConfusionMatrix{:,:};
confusionchart(M,["Normal","Anomaly"])
acc = sum(diag(M)) / sum(M,"all");
title("Accuracy: "+acc)

For more information about explainable classification decisions, see the Detect Image Anomalies Using Explainable FCDD Network (Computer Vision Toolbox) example.

Save the detector to a MAT-file for later use in MATLAB or in deployment workflows.

save('livePillDetector.mat','detector') 

Classify Live Images of Pills

You can use a custom video preview from a camera to display live classification of pills as normal or anomalous. This section demonstrates how to create a custom preview update callback function to process live images, identify individual pills, classify each pill, and show classification results overlaid with the camera preview video. You can find the code from this section as well as the update preview callback function attached to this example as supporting files.

Acquire images using a webcam with the videoinput interface at a resolution of 1280-by-720. Then, use a custom preview update callback function to identify each pill using the imfindcircles function, since the pills are circular. Crop the section of the camera image around each pill and pass it to the detector for classification. Based on the classification decision, display a label on each pill indicating whether it is a normal or anomalous pill. Normal pills are labeled as Good and anomalous pills are labeled as Bad in the preview window.

Load the anomaly detector.

load('livePillDetector.mat');

Create a connection to the webcam and specify appropriate values for the device-specific properties. The following device-specific property values are optimized for this hardware setup used originally for this example. Your setup might require a different configuration.

vid = videoinput('winvideo',1,'YUY2_1280x720');
vid.ReturnedColorSpace = "rgb";

nBands = vid.NumberOfBands;
vidRes = vid.ROIPosition;
imWidth = vidRes(3);
imHeight = vidRes(4);

src = getselectedsource(vid);
src.ExposureMode = "manual";
src.Exposure = -11;
src.FocusMode = "manual";
src.Focus = 11;
src.WhiteBalanceMode = "manual";
src.WhiteBalance = 2800;
src.FrameRate = "20.0000";

Create a figure window and axes in the figure. Then create the image object in which you want to display the video preview data. The size of the image object must match the dimensions of the video frames. Add a scroll panel to the image.

hFig = uifigure('Toolbar','none',...
       'Menubar', 'none',...
       'NumberTitle','Off',...
       'AutoResizeChildren','Off',...
       'Name','Live Pill Classification');
hAxis = uiaxes(hFig);
disableDefaultInteractivity(hAxis);
hImage = image(zeros(imHeight, imWidth, nBands),'Parent',hAxis);
imscrollpanel(hFig,hImage);

Configure the update preview window callback function and the detector as application-defined data on the image object. To define the mypreview_fcn callback function, refer to the Perform Custom Processing of Preview Data section.

setappdata(hImage,'UpdatePreviewWindowFcn',@mypreview_fcn);
setappdata(hImage,'Detector',detector);

Preview the video data in the custom figure window.

preview(vid,hImage);

Perform Custom Processing of Preview Data

Create a callback function mypreview_fcn that processes each frame and identifies whether pills are normal or dirt. This callback function is called for each acquired frame when you call the preview function.

The mypreview_fcn callback function performs the following:

function mypreview_fcn(obj,event,hImage)

    persistent detector;
    persistent ImgSize;
  
    if isempty(detector) && isempty(ImgSize)
        % Anomaly detector 
        detector = getappdata(hImage,'Detector');

        % Width and height of images used during calibration
        ImgSize = [352 288];
    end
  
    % Find circles (pills) in the current image frame
    img = event.Data;
    radiusRange = [30 80];
    circles = imfindcircles(img,radiusRange);

    % Use classifier if circles are found
    if ~isempty(circles)

        % Loop through all circles
        for i = 1:size(circles,1)

            % Crop image around the circle (pill)
            % [pos1, pos2] - top-left corner pixel position
            % ImgSize - width and height from [pos1, pos2]
            
            pos1 = max(circles(i,1)-ImgSize(1)/2,0);
            pos2 = max(circles(i,2)-ImgSize(2)/2,0);
            
            croppedImage = imcrop(img,[pos1, pos2,ImgSize(1),ImgSize(2)]);
            
            if ~isempty(croppedImage)
                % Classify cropped image and assign a text label in the
                % center of the circle
                decision = classify(detector, croppedImage);

                if decision
                    img = insertText(img,circles(i,:),"Bad", TextColor="Red",FontSize=14);
                else
                    img = insertText(img,circles(i,:),"Good", TextColor="Green",FontSize=14);
                end
            end
        end
    end
    hImage.CData = img;
end

This code is expected to classify images correctly if the camera's field of view contains one pill. If the field of view contains multiple pills, the distance between the pills must be large enough so that the cropped images do not contain more than one pill.

Deploy Live Image Classification as Standalone Application

You can deploy the live image classification of pills as a standalone application using the Application Compiler (MATLAB Compiler) app. You must have a license for MATLAB Compiler. Once you create the standalone application, you can deploy it to multiple machines without additional MATLAB licenses.

You must do the following in the Application Compiler app to create the standalone application.