I am trying to develop a script which will detect pixelation from LiveTV from an external camera. To test my script I have been using a short snippet of LiveTV which has two instances of pixelation.
See Google Drive below for video: https://drive.google.com/file/d/1f339HJSWKhyPr1y5sf9tWW4vcXgBOVbz/view?usp=sharing
Currently I am able to filter out most of the noise in the video, and detect the pixelation. However, I am also detecting the white text (given the intensity of the text it gets picked up by the kernel I am applying).
See the code below:
import cv2
import numpy as np
cap = cv2.VideoCapture("./hgtv_short.ts")
while True:
success, image = cap.read()
gray = cv2.cvtColor(src=image, code=cv2.COLOR_BGR2GRAY)
sharpen_kernel = np.array([[.4, .4], [-2.25, -2.25], [.4, .4]])
sharpen = cv2.filter2D(src=gray, ddepth=-1, kernel=sharpen_kernel)
sharpe = sharpen + 128
canny = cv2.Canny(image=sharpe, threshold1=245, threshold2=255, edges=1, apertureSize=3, L2gradient=True)
white = np.where(canny != [0])
coordinates = zip(white[1], white[0])
for p in coordinates:
cv2.circle(canny, p, 30, (200, 0, 0), 2)
cv2.imshow('image', image)
cv2.imshow('edges', canny)
cv2.waitKey(1)
What I would like to do is apply a threshold and findContours to the given coordinates to see if text is in the region. Then I can discern between actual pixelation and text.
NOTE: If anyone has any other ideas on finding pixelation I am open to suggestions.
UPDATE Here is a screenshot from the video showing the type of pixelation I am looking for in this video (macro-blocking) to be specific.
Image
Edges
From the above Images you can see that I am detecting the macro-blocking, but also the white text. I would like to be able to discern between text and actual macro-blocking.
SECOND UPDATE After more trial and error, I found that it will be best to use some sort of reference model to help predict when an image is showing macro-blocking, pixelation, artifacts, etc...
I have decided to use the hog(Histogram of Oriented Gradients) descriptor to create my feature vector. I have created to functions, one loops through the GOOD images and the other the BAD images:
def pos_train_set(self):
print("Starting to Gather Positive Photos")
for pos_file in glob.iglob(os.path.join(self.base_path, "Bad_Images", "*.jpg")):
pos_img = cv2.imread(pos_file, 1)
pos_img = cv2.resize(pos_img, self.winSize, interpolation=cv2.CV_32F)
pos_des = self.hog.compute(pos_img)
pos_des = cv2.normalize(pos_des, None)
self.labels.append(1)
self.training_data.append(pos_des)
print("Gathered Positive Photos")
def neg_train_set(self):
print("Starting to Gather Negative Photos")
for neg_file in glob.iglob(os.path.join(self.base_path, "Good_Images", "*.jpg")):
neg_img = cv2.imread(neg_file, 1)
neg_img = cv2.resize(neg_img, self.winSize, interpolation=cv2.CV_32F)
neg_des = self.hog.compute(neg_img)
neg_des = cv2.normalize(neg_des, None)
self.labels.append(0)
self.training_data.append(neg_des)
print("Gathered Negative Photos")
I then train my model using the SVM(Support Vector Machines) classification algorithm.
def train_set(self):
print("Starting to Convert")
td = np.float32(self.training_data)
lab = np.array(self.labels)
print("Converted List")
print("Starting Shuffle")
rand = np.random.RandomState(10)
shuffle = rand.permutation(len(td))
td = td[shuffle]
lab = lab[shuffle]
print("Shuffled List")
print("Starting SVM")
svm = cv2.ml.SVM_create()
svm.setType(cv2.ml.SVM_C_SVC)
# Exponential Chi2 kernel, similar to the RBF kernel: K(xi,xj)=e−γχ2(xi,xj),χ2(xi,xj)=(xi−xj)2/(xi+xj),γ>0.
svm.setKernel(cv2.ml.SVM_CHI2)
svm.setTermCriteria((cv2.TERM_CRITERIA_MAX_ITER, 100, 1e-6))
svm.setGamma(5.383)
svm.setC(2.67)
print("Starting Training")
svm.train(td, cv2.ml.ROW_SAMPLE, lab)
print("Saving to .yml")
svm.save(os.path.join(self.base_path, "svm_model.yml"))
I then use that SVM model to try and predict if an image is a 1 (Bad Image) or a 0 (Good Image). With the help of the kernel and edge detection I used in my first attempt:
def predict(self):
svm = cv2.ml.SVM_load("./svm_model.yml")
for file in self.files:
os.mkdir(os.path.join(self.base_path, "1_Frames", os.path.basename(file)))
print(f"Starting predict on {file}")
cap = cv2.VideoCapture(file)
while cap.isOpened():
success, image = cap.read(1)
if success:
img = cv2.resize(image, self.winSize, interpolation=cv2.CV_32F)
test_data = self.hog.compute(img)
test_data = cv2.normalize(test_data, None)
test_data = np.float32(test_data)
test_data = np.transpose(test_data)
if not np.any(test_data):
print("Invalid Dimension")
success, image = cap.read(1)
print(f"New Frame {success}")
else:
response = svm.predict(test_data)[1]
if response == 1:
gray = cv2.cvtColor(src=image, code=cv2.COLOR_BGR2GRAY)
sharpen_kernel = np.array([[.4, .4], [-2.25, -2.25], [.4, .4]])
sharpen = cv2.filter2D(src=gray, ddepth=-1, kernel=sharpen_kernel)
sharpe = sharpen + 128
canny = cv2.Canny(image=sharpe, threshold1=245, threshold2=255, edges=1, apertureSize=3, L2gradient=True)
white = np.where(canny != [0])
if not len(white[0]) == 0:
cv2.imwrite(os.path.join(self.base_path, '1_Frames', os.path.basename(file), f'found_{self.x}.jpg'), image)
success, image = cap.read(1)
self.x += 1
else:
success, image = cap.read(1)
pass
else:
cv2.imwrite(os.path.join(self.base_path, '0_Frames', f'found_{self.y}.jpg'), image)
success, image = cap.read(1)
self.y += 1
else:
break
cap.release()
cv2.destroyAllWindows()
This method seems to work well, but I am still open to any further ideas of suggestions. I posted this new update in hopes it may assist someone else looking for suggestions on how to detect issues in images.