public bool IsFace(Bitmap image)
{
if (image == null)
{
throw new ArgumentNullException(nameof(image));
}
using (var windowedImageForFeatureExtraction = image.ExtractImageSectionAndResize(new Rectangle(new Point(0, 0), image.Size), new Size(_sampleWidth, _sampleHeight)))
{
return(_svm.Decide(
FeatureExtractor.GetFor(windowedImageForFeatureExtraction, _blockSize, optionalHogPreviewImagePath: null, normaliser: _normaliser).ToArray()
));
}
}
public static IClassifyPotentialFaces TrainFromCaltechData(
DirectoryInfo caltechWebFacesSourceImageFolder,
FileInfo groundTruthTextFile,
int sampleWidth,
int sampleHeight,
int blockSize,
int minimumNumberOfImagesToTrainWith,
Normaliser normaliser,
Action <string> logger)
{
if (caltechWebFacesSourceImageFolder == null)
{
throw new ArgumentNullException(nameof(caltechWebFacesSourceImageFolder));
}
if (groundTruthTextFile == null)
{
throw new ArgumentNullException(nameof(groundTruthTextFile));
}
if (sampleWidth <= 0)
{
throw new ArgumentOutOfRangeException(nameof(sampleWidth));
}
if (sampleHeight <= 0)
{
throw new ArgumentOutOfRangeException(nameof(sampleHeight));
}
if (blockSize <= 0)
{
throw new ArgumentOutOfRangeException(nameof(blockSize));
}
if (minimumNumberOfImagesToTrainWith <= 0)
{
throw new ArgumentOutOfRangeException(nameof(minimumNumberOfImagesToTrainWith));
}
if (normaliser == null)
{
throw new ArgumentNullException(nameof(normaliser));
}
if (logger == null)
{
throw new ArgumentNullException(nameof(logger));
}
var timer = Stopwatch.StartNew();
var trainingDataOfHogsAndIsFace = new List <Tuple <double[], bool> >();
var numberOfImagesThatLastProgressMessageWasShownAt = 0;
const int numberOfImagesToProcessBeforeShowingUpdateMessage = 20;
foreach (var imagesFromSingleReferenceImage in ExtractPositiveAndNegativeTrainingDataFromCaltechWebFaces(sampleWidth, sampleHeight, groundTruthTextFile, caltechWebFacesSourceImageFolder))
{
// We want to train using the same number of positive images as negative images. It's possible that we were unable to extract as many non-face regions from the source
// image as we did face regions. In this case, discount the image and move on to the next one.
var numberOfPositiveImagesExtracted = imagesFromSingleReferenceImage.Count(imageAndIsFaceDecision => imageAndIsFaceDecision.Item2);
var numberOfNegativeImagesExtracted = imagesFromSingleReferenceImage.Count(imageAndIsFaceDecision => !imageAndIsFaceDecision.Item2);
if (numberOfPositiveImagesExtracted != numberOfNegativeImagesExtracted)
{
foreach (var image in imagesFromSingleReferenceImage.Select(imageAndIsFaceDecision => imageAndIsFaceDecision.Item1))
{
image.Dispose();
}
continue;
}
foreach (var imageAndIsFaceDecision in imagesFromSingleReferenceImage)
{
var image = imageAndIsFaceDecision.Item1;
var isFace = imageAndIsFaceDecision.Item2;
trainingDataOfHogsAndIsFace.Add(Tuple.Create(
FeatureExtractor.GetFor(image, blockSize, optionalHogPreviewImagePath: null, normaliser: normaliser).ToArray(),
isFace
));
image.Dispose();
}
var approximateNumberOfImagesProcessed = (int)Math.Floor((double)trainingDataOfHogsAndIsFace.Count / numberOfImagesToProcessBeforeShowingUpdateMessage) * numberOfImagesToProcessBeforeShowingUpdateMessage;
if (approximateNumberOfImagesProcessed > numberOfImagesThatLastProgressMessageWasShownAt)
{
logger("Processed " + approximateNumberOfImagesProcessed + " images");
numberOfImagesThatLastProgressMessageWasShownAt = approximateNumberOfImagesProcessed;
}
if (trainingDataOfHogsAndIsFace.Count >= minimumNumberOfImagesToTrainWith)
{
break;
}
}
if (trainingDataOfHogsAndIsFace.Count < minimumNumberOfImagesToTrainWith)
{
throw new Exception($"After loaded all data, there are only {trainingDataOfHogsAndIsFace.Count} training images but {minimumNumberOfImagesToTrainWith} were requested");
}
logger("Time to load image data: " + timer.Elapsed.TotalSeconds.ToString("0.00") + "s");
timer.Restart();
var smo = new SequentialMinimalOptimization <Linear>();
var inputs = trainingDataOfHogsAndIsFace.Select(dataAndResult => dataAndResult.Item1).ToArray();
var outputs = trainingDataOfHogsAndIsFace.Select(dataAndResult => dataAndResult.Item2).ToArray();
var svm = smo.Learn(inputs, outputs);
logger("Time to teach SVM: " + timer.Elapsed.TotalSeconds.ToString("0.00") + "s");
timer.Restart();
// The SVM kernel contains lots of information from the training process which can be reduced down (from the Compress method's summary documentation: "If this machine has
// a linear kernel, compresses all support vectors into a single parameter vector)". This additional data is of no use to use so we can safely get rid of it - this will
// be beneficial if we decide to persist the trained SVM since they will be less data to serialise.
svm.Compress();
logger("Time to compress SVM: " + timer.Elapsed.TotalSeconds.ToString("0.00") + "s");
timer.Restart();
var predicted = svm.Decide(inputs);
var error = new ZeroOneLoss(outputs).Loss(predicted);
if (error > 0)
{
logger("*** Generated SVM has non-zero error against training data: " + error);
}
logger("Time to test SVM against training data: " + timer.Elapsed.TotalSeconds.ToString("0.00") + "s");
timer.Restart();
return(new SvmClassifier(svm, sampleWidth, sampleHeight, blockSize, normaliser));
}