Open Source Computer Vision Library https://opencv.org/
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'''
SVN and KNearest digit recognition.
Sample loads a dataset of handwritten digits from 'digits.png'.
Then it trains a SVN and KNearest classifiers on it and evaluates
their accuracy. Moment-based image deskew is used to improve
the recognition accuracy.
Usage:
digits.py
'''
import numpy as np
import cv2
from multiprocessing.pool import ThreadPool
from common import clock, mosaic
SZ = 20 # size of each digit is SZ x SZ
CLASS_N = 10
DIGITS_FN = 'digits.png'
def load_digits(fn):
print 'loading "%s" ...' % fn
digits_img = cv2.imread(fn, 0)
h, w = digits_img.shape
digits = [np.hsplit(row, w/SZ) for row in np.vsplit(digits_img, h/SZ)]
digits = np.array(digits).reshape(-1, SZ, SZ)
labels = np.repeat(np.arange(CLASS_N), len(digits)/CLASS_N)
return digits, labels
def deskew(img):
m = cv2.moments(img)
if abs(m['mu02']) < 1e-2:
return img.copy()
skew = m['mu11']/m['mu02']
M = np.float32([[1, skew, -0.5*SZ*skew], [0, 1, 0]])
img = cv2.warpAffine(img, M, (SZ, SZ), flags=cv2.WARP_INVERSE_MAP | cv2.INTER_LINEAR)
return img
class StatModel(object):
def load(self, fn):
self.model.load(fn)
def save(self, fn):
self.model.save(fn)
class KNearest(StatModel):
def __init__(self, k = 3):
self.k = k
self.model = cv2.KNearest()
def train(self, samples, responses):
self.model = cv2.KNearest()
self.model.train(samples, responses)
def predict(self, samples):
retval, results, neigh_resp, dists = self.model.find_nearest(samples, self.k)
return results.ravel()
class SVM(StatModel):
def __init__(self, C = 1, gamma = 0.5):
self.params = dict( kernel_type = cv2.SVM_RBF,
svm_type = cv2.SVM_C_SVC,
C = C,
gamma = gamma )
self.model = cv2.SVM()
def train(self, samples, responses):
self.model = cv2.SVM()
self.model.train(samples, responses, params = self.params)
def predict(self, samples):
return self.model.predict_all(samples).ravel()
def evaluate_model(model, digits, samples, labels):
resp = model.predict(samples)
err = (labels != resp).mean()
print 'error: %.2f %%' % (err*100)
confusion = np.zeros((10, 10), np.int32)
for i, j in zip(labels, resp):
confusion[i, j] += 1
print 'confusion matrix:'
print confusion
print
vis = []
for img, flag in zip(digits, resp == labels):
img = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)
if not flag:
img[...,:2] = 0
vis.append(img)
return mosaic(25, vis)
if __name__ == '__main__':
print __doc__
digits, labels = load_digits(DIGITS_FN)
print 'preprocessing...'
# shuffle digits
rand = np.random.RandomState(12345)
shuffle = rand.permutation(len(digits))
digits, labels = digits[shuffle], labels[shuffle]
digits2 = map(deskew, digits)
samples = np.float32(digits2).reshape(-1, SZ*SZ) / 255.0
train_n = int(0.9*len(samples))
cv2.imshow('test set', mosaic(25, digits[train_n:]))
digits_train, digits_test = np.split(digits2, [train_n])
samples_train, samples_test = np.split(samples, [train_n])
labels_train, labels_test = np.split(labels, [train_n])
print 'training KNearest...'
model = KNearest(k=1)
model.train(samples_train, labels_train)
vis = evaluate_model(model, digits_test, samples_test, labels_test)
cv2.imshow('KNearest test', vis)
print 'training SVM...'
model = SVM(C=4.66, gamma=0.08)
model.train(samples_train, labels_train)
vis = evaluate_model(model, digits_test, samples_test, labels_test)
cv2.imshow('SVM test', vis)
print 'saving SVM as "digits_svm.dat"...'
model.save('digits_svm.dat')
cv2.waitKey(0)