简单图像分类

''' @author: Tiejian Zhang @email: zhangtj_pku@hotmail.com @method: SIFT -> k-means -> SVM ''' import cv2 import numpy as np TrainSetInfo = { "car" : 40, "city" : 20, "dog" : 30, "earth" : 15, "fireworks" : 20, "flowers" : 20, "fruits" : 20, "glass" : 20, "gold" : 15, "gun" : 20, "plane" : 40, "sky" : 30, "worldcup" : 40 } TestSetInfo = { "car" : 119, "city" : 59, "dog" : 49, "earth" : 24, "fireworks" : 54, "flowers" : 63, "fruits" : 78, "glass" : 52, "gold" : 44, "gun" : 44, "plane" : 102, "sky" : 78, "worldcup" : 131 } def calcSiftFeature(img): gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) sift = cv2.SIFT(200) # max number of SIFT points is 200 kp, des = sift.detectAndCompute(gray, None) return des def calcFeatVec(features, centers): featVec = np.zeros((1, 50)) for i in range(0, features.shape[0]): fi = features[i] diffMat = np.tile(fi, (50, 1)) - centers sqSum = (diffMat**2).sum(axis=1) dist = sqSum**0.5 sortedIndices = dist.argsort() idx = sortedIndices[0] # index of the nearest center featVec[0][idx] += 1 return featVec def initFeatureSet(): for name, count in TrainSetInfo.items(): dir = "TrainSet/" + name + "/" featureSet = np.float32([]).reshape(0,128) print "Extract features from training set" + name + "..." for i in range(1, count + 1): filename = dir + name + " (" + str(i) + ").jpg" img = cv2.imread(filename) des = calcSiftFeature(img) featureSet = np.append(featureSet, des, axis=0) featCnt = featureSet.shape[0] print str(featCnt) + " features in " + str(count) + " images\n" # save featureSet to file filename = "Temp/features/" + name + ".npy" np.save(filename, featureSet) def learnVocabulary(): wordCnt = 50 for name, count in TrainSetInfo.items(): filename = "Temp/features/" + name + ".npy" features = np.load(filename) print "Learn vocabulary of " + name + "..." # use k-means to cluster a bag of features criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 20, 0.1) flags = cv2.KMEANS_RANDOM_CENTERS compactness, labels, centers = cv2.kmeans(features, wordCnt, criteria, 20, flags) # save vocabulary(a tuple of (labels, centers)) to file filename = "Temp/vocabulary/" + name + ".npy" np.save(filename, (labels, centers)) print "Done\n" def trainClassifier(): trainData = np.float32([]).reshape(0, 50) response = np.float32([]) dictIdx = 0 for name, count in TrainSetInfo.items(): dir = "TestSet/" + name + "/" labels, centers = np.load("Temp/vocabulary/" + name + ".npy") print "Init training data of " + name + "..." for i in range(1, count + 1): filename = dir + name + " (" + str(i) + ").jpg" img = cv2.imread(filename) features = calcSiftFeature(img) featVec = calcFeatVec(features, centers) trainData = np.append(trainData, featVec, axis=0) res = np.repeat(np.float32([dictIdx]), count) response = np.append(response, res) dictIdx += 1 print "Done\n" print "Now train svm classifier..." trainData = np.float32(trainData) response = response.reshape(-1, 1) svm = cv2.SVM() svm.train_auto(trainData, response, None, None, None) # select best params svm.save("svm.clf") print "Done\n" def classify(): svm = cv2.SVM() svm.load("svm.clf") total = 0; correct = 0; dictIdx = 0 for name, count in TestSetInfo.items(): crt = 0 dir = "TestSet/" + name + "/" labels, centers = np.load("Temp/vocabulary/" + name + ".npy") print "Classify on TestSet " + name + ":" for i in range(1, count + 1): filename = dir + name + " (" + str(i) + ").jpg" img = cv2.imread(filename) features = calcSiftFeature(img) featVec = getFeatureVector(features, centers) case = np.float32(featVec) if (dictIdx == svm.predict(case)): crt += 1 print "Accuracy: " + str(crt) + " / " + str(count) + "\n" total += count correct += crt dictIdx += 1 print "Total accuracy: " + str(correct) + " / " + str(total) if __name__ == "__main__": initFeatureSet() learnVocabulary() trainClassifier() classify()