Difference between revisions of "Example Scene Classification"

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<center>
<center>
<gallery widths=300px heights=300px>
<gallery widths=450px heights=340px>
File:Confusion_matrix.png | Confusion matrix created from the code below.  Perfect results would be black along the diagonal.
File:Confusion_matrix.png | Confusion matrix created from the code below.  Perfect results would be black along the diagonal.
</gallery>
</gallery>
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Example Code:
Example Code:
* [https://github.com/lessthanoptimal/BoofCV/blob/v0.20/examples/src/boofcv/examples/recognition/ExampleClassifySceneKnn.java ExampleClassifySceneKnn.java ]
* [https://github.com/lessthanoptimal/BoofCV/blob/v0.31/examples/src/main/java/boofcv/examples/recognition/ExampleClassifySceneKnn.java ExampleClassifySceneKnn.java ]


Concepts:
Concepts:
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* Clustering
* Clustering
* k-NN classifier
* k-NN classifier
Related Examples:
* [[Example_Image_Classification|Image Classification]]


= Example Code =
= Example Code =
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public static int NUM_NEIGHBORS = 10;
public static int NUM_NEIGHBORS = 10;
public static int MAX_KNN_ITERATIONS = 100;
public static int MAX_KNN_ITERATIONS = 100;
public static double DESC_SCALE = 1.0;
public static int DESC_SKIP = 8;


// Files intermediate results are stored in
// Files intermediate results are stored in
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// Algorithms
// Algorithms
ClusterVisualWords cluster;
ClusterVisualWords cluster;
DescribeImageDense<ImageUInt8,TupleDesc_F64> describeImage;
DescribeImageDense<GrayU8,TupleDesc_F64> describeImage;
NearestNeighbor<HistogramScene> nn;
NearestNeighbor<HistogramScene> nn;


ClassifierKNearestNeighborsBow<ImageUInt8,TupleDesc_F64> classifier;
ClassifierKNearestNeighborsBow<GrayU8,TupleDesc_F64> classifier;


// Storage for detected features
public ExampleClassifySceneKnn(final DescribeImageDense<GrayU8, TupleDesc_F64> describeImage,
FastQueue<TupleDesc_F64> features;
 
public ExampleClassifySceneKnn(final DescribeImageDense<ImageUInt8, TupleDesc_F64> describeImage,
  ComputeClusters<double[]> clusterer,
  ComputeClusters<double[]> clusterer,
  NearestNeighbor<HistogramScene> nn) {
  NearestNeighbor<HistogramScene> nn) {
Line 78: Line 76:
this.cluster = new ClusterVisualWords(clusterer, describeImage.createDescription().size(),0xFEEDBEEF);
this.cluster = new ClusterVisualWords(clusterer, describeImage.createDescription().size(),0xFEEDBEEF);
this.nn = nn;
this.nn = nn;
// This list can be dynamically grown.  However TupleDesc doesn't have a no argument constructor so
// you must to it how to cosntruct the data
features = new FastQueue<TupleDesc_F64>(TupleDesc_F64.class,true) {
@Override
protected TupleDesc_F64 createInstance() {
return describeImage.createDescription();
}
};
}
}


Line 124: Line 113:


// computes features in the training image set
// computes features in the training image set
features.reset();
List<TupleDesc_F64> features = new ArrayList<>();
for( String scene : train.keySet() ) {
for( String scene : train.keySet() ) {
List<String> imagePaths = train.get(scene);
List<String> imagePaths = train.get(scene);
Line 130: Line 119:


for( String path : imagePaths ) {
for( String path : imagePaths ) {
ImageUInt8 image = UtilImageIO.loadImage(path, ImageUInt8.class);
GrayU8 image = UtilImageIO.loadImage(path, GrayU8.class);
describeImage.process(image,features,null);
describeImage.process(image);
 
// the descriptions will get recycled on the next call, so create a copy
for( TupleDesc_F64 d : describeImage.getDescriptions() ) {
features.add( d.copy() );
}
}
}
}
}
// add the features to the overall list which the clusters will be found inside of
// add the features to the overall list which the clusters will be found inside of
for (int i = 0; i < features.size; i++) {
for (int i = 0; i < features.size(); i++) {
cluster.addReference(features.get(i));
cluster.addReference(features.get(i));
}
}
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// Can use this classifier with saved results and avoid the
// Can use this classifier with saved results and avoid the


classifier = new ClassifierKNearestNeighborsBow<ImageUInt8,TupleDesc_F64>(nn,describeImage,featuresToHistogram);
classifier = new ClassifierKNearestNeighborsBow<>(nn, describeImage, featuresToHistogram);
classifier.setClassificationData(memory, getScenes().size());
classifier.setClassificationData(memory, getScenes().size());
classifier.setNumNeighbors(NUM_NEIGHBORS);
classifier.setNumNeighbors(NUM_NEIGHBORS);
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List<HistogramScene> memory;// Processed results which will be passed into the k-NN algorithm
List<HistogramScene> memory;// Processed results which will be passed into the k-NN algorithm
memory = new ArrayList<HistogramScene>();
memory = new ArrayList<>();


for( int sceneIndex = 0; sceneIndex < scenes.size(); sceneIndex++ ) {
for( int sceneIndex = 0; sceneIndex < scenes.size(); sceneIndex++ ) {
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for (String path : imagePaths) {
for (String path : imagePaths) {
ImageUInt8 image = UtilImageIO.loadImage(path, ImageUInt8.class);
GrayU8 image = UtilImageIO.loadImage(path, GrayU8.class);


// reset before processing a new image
// reset before processing a new image
featuresToHistogram.reset();
featuresToHistogram.reset();
features.reset();
describeImage.process(image);
describeImage.process(image, features,null);
for ( TupleDesc_F64 d : describeImage.getDescriptions() ) {
for (int i = 0; i < features.size; i++) {
featuresToHistogram.addFeature(d);
featuresToHistogram.addFeature(features.get(i));
}
}
featuresToHistogram.process();
featuresToHistogram.process();
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@Override
@Override
protected int classify(String path) {
protected int classify(String path) {
ImageUInt8 image = UtilImageIO.loadImage(path, ImageUInt8.class);
GrayU8 image = UtilImageIO.loadImage(path, GrayU8.class);


return classifier.classify(image);
return classifier.classify(image);
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public static void main(String[] args) {
public static void main(String[] args) {


DescribeImageDense<ImageUInt8,TupleDesc_F64> desc = (DescribeImageDense)
ConfigDenseSurfFast surfFast = new ConfigDenseSurfFast(new DenseSampling(8,8));
FactoryDescribeImageDense.surfFast(null,
ConfigDenseSurfStable surfStable = new ConfigDenseSurfStable(new DenseSampling(8,8));
new ConfigDenseSample(DESC_SCALE, DESC_SKIP, DESC_SKIP), ImageUInt8.class);
ConfigDenseSift sift = new ConfigDenseSift(new DenseSampling(6,6));
ConfigDenseHoG hog = new ConfigDenseHoG();
 
DescribeImageDense<GrayU8,TupleDesc_F64> desc = (DescribeImageDense)
FactoryDescribeImageDense.surfFast(surfFast, GrayU8.class);
// FactoryDescribeImageDense.surfStable(surfStable, GrayU8.class);
// FactoryDescribeImageDense.sift(sift, GrayU8.class);
// FactoryDescribeImageDense.hog(hog, ImageType.single(GrayU8.class));


ComputeClusters<double[]> clusterer = FactoryClustering.kMeans_F64(null, MAX_KNN_ITERATIONS, 20, 1e-6);
ComputeClusters<double[]> clusterer = FactoryClustering.kMeans_F64(null, MAX_KNN_ITERATIONS, 20, 1e-6);
clusterer.setVerbose(true);
clusterer.setVerbose(true);


NearestNeighbor<HistogramScene> nn = FactoryNearestNeighbor.exhaustive();
int pointDof = desc.createDescription().size();
NearestNeighbor<HistogramScene> nn = FactoryNearestNeighbor.exhaustive(new KdTreeHistogramScene_F64(pointDof));
ExampleClassifySceneKnn example = new ExampleClassifySceneKnn(desc,clusterer,nn);
ExampleClassifySceneKnn example = new ExampleClassifySceneKnn(desc,clusterer,nn);


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if( !trainingDir.exists() || !testingDir.exists() ) {
if( !trainingDir.exists() || !testingDir.exists() ) {
System.err.println("Please follow instructions in data/applet/learning/scene and download the");
String addressSrc = "http://boofcv.org/notwiki/largefiles/bow_data_v001.zip";
System.err.println("required files");
File dst = new File(trainingDir.getParentFile(),"bow_data_v001.zip");
System.exit(1);
try {
DeepBoofDataBaseOps.download(addressSrc, dst);
DeepBoofDataBaseOps.decompressZip(dst, dst.getParentFile(), true);
System.out.println("Download complete!");
} catch( IOException e ) {
throw new RuntimeException(e);
}
} else {
System.out.println("Delete and download again if there are file not found errors");
System.out.println("   "+trainingDir);
System.out.println("  "+testingDir);
}
}


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// Show confusion matrix
// Show confusion matrix
// Not the best coloration scheme...  perfect = red diagonal and blue elsewhere.
// Not the best coloration scheme...  perfect = red diagonal and blue elsewhere.
ShowImages.showWindow(new ConfusionMatrixPanel(confusion.getMatrix(), 400, true), "Confusion Matrix", true);
ShowImages.showWindow(new ConfusionMatrixPanel(
confusion.getMatrix(),example.getScenes(), 400, true), "Confusion Matrix", true);


// For SIFT descriptor the accuracy is          54.0%
// For  "fast"  SURF descriptor the accuracy is 52.2%
// For  "fast"  SURF descriptor the accuracy is 52.2%
// For "stable" SURF descriptor the accuracy is 49.4%
// For "stable" SURF descriptor the accuracy is 49.4%
// For HOG                                      53.3%


// This is interesting. When matching images "stable" is significantly better than "fast"
// SURF results are interesting. "Stable" is significantly better than "fast"!
// One explanation is that the descriptor for "fast" samples a smaller region than "stable", by a
// One explanation is that the descriptor for "fast" samples a smaller region than "stable", by a
// couple of pixels at scale of 1.  Thus there is less overlap between the features.
// couple of pixels at scale of 1.  Thus there is less overlap between the features.

Revision as of 19:58, 16 October 2018

Scene classification is the problem where you are presented with an image and you need to classify it as belonging to a known set. The example below demonstrates how to perform scene classification using dense SURF features and a nearest neighbour classifier. See code documentation for a more detailed discussion.

Example Code:

Concepts:

  • Scene Classification
  • Dense Image Features
  • Clustering
  • k-NN classifier

Related Examples:

Example Code

/**
 * <p>
 * Example of how to train a K-NN bow-of-word classifier for scene recognition.  The resulting classifier
 * produces results which are correct 52.2% of the time.  To provide a point of comparison, randomly selecting
 * a scene is about 6.7% accurate, SVM One vs One RBF classifier can produce accuracy of around 74% and
 * other people using different techniques claim to have achieved around 85% accurate with more advanced
 * techniques.
 * </p>
 *
 * Training Steps:
 * <ol>
 * <li>Compute dense SURF features across the training data set.</li>
 * <li>Cluster using k-means to create works.</li>
 * <li>For each image compute the histogram of words found in the image</li>
 * <li>Save word histograms and image scene labels in a classifier</li>
 * </ol>
 *
 * Testing Steps:
 * <ol>
 * <li>For each image in the testing data set compute its histogram</li>
 * <li>Look up the k-nearest-neighbors for that histogram</li>
 * <li>Classify an image by by selecting the scene type with the most neighbors</li>
 * </ol>
 *
 * <p>NOTE: Scene recognition is still very much a work in progress in BoofCV and the code is likely to be
 * significantly modified in the future.</p>
 *
 * @author Peter Abeles
 */
public class ExampleClassifySceneKnn extends LearnSceneFromFiles {

	// Tuning parameters
	public static int NUMBER_OF_WORDS = 100;
	public static boolean HISTOGRAM_HARD = true;
	public static int NUM_NEIGHBORS = 10;
	public static int MAX_KNN_ITERATIONS = 100;

	// Files intermediate results are stored in
	public static final String CLUSTER_FILE_NAME = "clusters.obj";
	public static final String HISTOGRAM_FILE_NAME = "histograms.obj";

	// Algorithms
	ClusterVisualWords cluster;
	DescribeImageDense<GrayU8,TupleDesc_F64> describeImage;
	NearestNeighbor<HistogramScene> nn;

	ClassifierKNearestNeighborsBow<GrayU8,TupleDesc_F64> classifier;

	public ExampleClassifySceneKnn(final DescribeImageDense<GrayU8, TupleDesc_F64> describeImage,
								   ComputeClusters<double[]> clusterer,
								   NearestNeighbor<HistogramScene> nn) {
		this.describeImage = describeImage;
		this.cluster = new ClusterVisualWords(clusterer, describeImage.createDescription().size(),0xFEEDBEEF);
		this.nn = nn;
	}

	/**
	 * Process all the data in the training data set to learn the classifications.  See code for details.
	 */
	public void learnAndSave() {
		System.out.println("======== Learning Classifier");

		// Either load pre-computed words or compute the words from the training images
		AssignCluster<double[]> assignment;
		if( new File(CLUSTER_FILE_NAME).exists() ) {
			assignment = UtilIO.load(CLUSTER_FILE_NAME);
		} else {
			System.out.println(" Computing clusters");
			assignment = computeClusters();
		}

		// Use these clusters to assign features to words
		FeatureToWordHistogram_F64 featuresToHistogram = new FeatureToWordHistogram_F64(assignment,HISTOGRAM_HARD);

		// Storage for the work histogram in each image in the training set and their label
		List<HistogramScene> memory;

		if( !new File(HISTOGRAM_FILE_NAME).exists() ) {
			System.out.println(" computing histograms");
			memory = computeHistograms(featuresToHistogram);
			UtilIO.save(memory,HISTOGRAM_FILE_NAME);
		}
	}

	/**
	 * Extract dense features across the training set.  Then clusters are found within those features.
	 */
	private AssignCluster<double[]> computeClusters() {
		System.out.println("Image Features");

		// computes features in the training image set
		List<TupleDesc_F64> features = new ArrayList<>();
		for( String scene : train.keySet() ) {
			List<String> imagePaths = train.get(scene);
			System.out.println("   " + scene);

			for( String path : imagePaths ) {
				GrayU8 image = UtilImageIO.loadImage(path, GrayU8.class);
				describeImage.process(image);

				// the descriptions will get recycled on the next call, so create a copy
				for( TupleDesc_F64 d : describeImage.getDescriptions() ) {
					features.add( d.copy() );
				}
			}
		}
		// add the features to the overall list which the clusters will be found inside of
		for (int i = 0; i < features.size(); i++) {
			cluster.addReference(features.get(i));
		}

		System.out.println("Clustering");
		// Find the clusters.  This can take a bit
		cluster.process(NUMBER_OF_WORDS);

		UtilIO.save(cluster.getAssignment(), CLUSTER_FILE_NAME);

		return cluster.getAssignment();
	}

	public void loadAndCreateClassifier() {
		// load results from a file
		List<HistogramScene> memory = UtilIO.load(HISTOGRAM_FILE_NAME);
		AssignCluster<double[]> assignment = UtilIO.load(CLUSTER_FILE_NAME);

		FeatureToWordHistogram_F64 featuresToHistogram = new FeatureToWordHistogram_F64(assignment,HISTOGRAM_HARD);


		// Provide the training results to K-NN and it will preprocess these results for quick lookup later on
		// Can use this classifier with saved results and avoid the

		classifier = new ClassifierKNearestNeighborsBow<>(nn, describeImage, featuresToHistogram);
		classifier.setClassificationData(memory, getScenes().size());
		classifier.setNumNeighbors(NUM_NEIGHBORS);
	}

	/**
	 * For all the images in the training data set it computes a {@link HistogramScene}.  That data structure
	 * contains the word histogram and the scene that the histogram belongs to.
	 */
	private List<HistogramScene> computeHistograms(FeatureToWordHistogram_F64 featuresToHistogram ) {

		List<String> scenes = getScenes();

		List<HistogramScene> memory;// Processed results which will be passed into the k-NN algorithm
		memory = new ArrayList<>();

		for( int sceneIndex = 0; sceneIndex < scenes.size(); sceneIndex++ ) {
			String scene = scenes.get(sceneIndex);
			System.out.println("   " + scene);
			List<String> imagePaths = train.get(scene);

			for (String path : imagePaths) {
				GrayU8 image = UtilImageIO.loadImage(path, GrayU8.class);

				// reset before processing a new image
				featuresToHistogram.reset();
				describeImage.process(image);
				for ( TupleDesc_F64 d : describeImage.getDescriptions() ) {
					featuresToHistogram.addFeature(d);
				}
				featuresToHistogram.process();

				// The histogram is already normalized so that it sums up to 1.  This provides invariance
				// against the overall number of features changing.
				double[] histogram = featuresToHistogram.getHistogram();

				// Create the data structure used by the KNN classifier
				HistogramScene imageHist = new HistogramScene(NUMBER_OF_WORDS);
				imageHist.setHistogram(histogram);
				imageHist.type = sceneIndex;

				memory.add(imageHist);
			}
		}
		return memory;
	}

	@Override
	protected int classify(String path) {
		GrayU8 image = UtilImageIO.loadImage(path, GrayU8.class);

		return classifier.classify(image);
	}

	public static void main(String[] args) {

		ConfigDenseSurfFast surfFast = new ConfigDenseSurfFast(new DenseSampling(8,8));
		ConfigDenseSurfStable surfStable = new ConfigDenseSurfStable(new DenseSampling(8,8));
		ConfigDenseSift sift = new ConfigDenseSift(new DenseSampling(6,6));
		ConfigDenseHoG hog = new ConfigDenseHoG();

		DescribeImageDense<GrayU8,TupleDesc_F64> desc = (DescribeImageDense)
				FactoryDescribeImageDense.surfFast(surfFast, GrayU8.class);
//				FactoryDescribeImageDense.surfStable(surfStable, GrayU8.class);
//				FactoryDescribeImageDense.sift(sift, GrayU8.class);
//				FactoryDescribeImageDense.hog(hog, ImageType.single(GrayU8.class));

		ComputeClusters<double[]> clusterer = FactoryClustering.kMeans_F64(null, MAX_KNN_ITERATIONS, 20, 1e-6);
		clusterer.setVerbose(true);

		int pointDof = desc.createDescription().size();
		NearestNeighbor<HistogramScene> nn = FactoryNearestNeighbor.exhaustive(new KdTreeHistogramScene_F64(pointDof));
		ExampleClassifySceneKnn example = new ExampleClassifySceneKnn(desc,clusterer,nn);

		File trainingDir = new File(UtilIO.pathExample("learning/scene/train"));
		File testingDir = new File(UtilIO.pathExample("learning/scene/test"));

		if( !trainingDir.exists() || !testingDir.exists() ) {
			String addressSrc = "http://boofcv.org/notwiki/largefiles/bow_data_v001.zip";
			File dst = new File(trainingDir.getParentFile(),"bow_data_v001.zip");
			try {
				DeepBoofDataBaseOps.download(addressSrc, dst);
				DeepBoofDataBaseOps.decompressZip(dst, dst.getParentFile(), true);
				System.out.println("Download complete!");
			} catch( IOException e ) {
				throw new RuntimeException(e);
			}
		} else {
			System.out.println("Delete and download again if there are file not found errors");
			System.out.println("   "+trainingDir);
			System.out.println("   "+testingDir);
		}

		example.loadSets(trainingDir, null, testingDir);
		// train the classifier
		example.learnAndSave();
		// now load it for evaluation purposes from the files
		example.loadAndCreateClassifier();

		// test the classifier on the test set
		Confusion confusion = example.evaluateTest();
		confusion.getMatrix().print();
		System.out.println("Accuracy = " + confusion.computeAccuracy());

		// Show confusion matrix
		// Not the best coloration scheme...  perfect = red diagonal and blue elsewhere.
		ShowImages.showWindow(new ConfusionMatrixPanel(
				confusion.getMatrix(),example.getScenes(), 400, true), "Confusion Matrix", true);

		// For SIFT descriptor the accuracy is          54.0%
		// For  "fast"  SURF descriptor the accuracy is 52.2%
		// For "stable" SURF descriptor the accuracy is 49.4%
		// For HOG                                      53.3%

		// SURF results are interesting. "Stable" is significantly better than "fast"!
		// One explanation is that the descriptor for "fast" samples a smaller region than "stable", by a
		// couple of pixels at scale of 1.  Thus there is less overlap between the features.

		// Reducing the size of "stable" to 0.95 does slightly improve performance to 50.5%, can't scale it down
		// much more without performance going down
	}
}