def extract_bv(image):
clahe = cv2.createCLAHE(clipLimit=2.0, tileGridSize=(8,8))
contrast_enhanced_green_fundus = clahe.apply(image)
# applying alternate sequential filtering (3 times closing opening)
r1 = cv2.morphologyEx(contrast_enhanced_green_fundus, cv2.MORPH_OPEN, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(5,5)), iterations = 1)
R1 = cv2.morphologyEx(r1, cv2.MORPH_CLOSE, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(5,5)), iterations = 1)
r2 = cv2.morphologyEx(R1, cv2.MORPH_OPEN, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(11,11)), iterations = 1)
R2 = cv2.morphologyEx(r2, cv2.MORPH_CLOSE, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(11,11)), iterations = 1)
r3 = cv2.morphologyEx(R2, cv2.MORPH_OPEN, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(23,23)), iterations = 1)
R3 = cv2.morphologyEx(r3, cv2.MORPH_CLOSE, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(23,23)), iterations = 1)
f4 = cv2.subtract(R3,contrast_enhanced_green_fundus)
f5 = clahe.apply(f4)
# removing very small contours through area parameter noise removal
ret,f6 = cv2.threshold(f5,15,255,cv2.THRESH_BINARY)
mask = np.ones(f5.shape[:2], dtype="uint8") * 255
im2, contours, hierarchy = cv2.findContours(f6.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)
for cnt in contours:
if cv2.contourArea(cnt) <= 200:
cv2.drawContours(mask, [cnt], -1, 0, -1)
im = cv2.bitwise_and(f5, f5, mask=mask)
ret,fin = cv2.threshold(im,15,255,cv2.THRESH_BINARY_INV)
newfin = cv2.erode(fin, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(3,3)), iterations=1)
# removing blobs of microaneurysm & unwanted bigger chunks taking in consideration they are not straight lines like blood
# vessels and also in an interval of area
fundus_eroded = cv2.bitwise_not(newfin)
xmask = np.ones(image.shape[:2], dtype="uint8") * 255
x1, xcontours, xhierarchy = cv2.findContours(fundus_eroded.copy(),cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)
for cnt in xcontours:
shape = "unidentified"
peri = cv2.arcLength(cnt, True)
approx = cv2.approxPolyDP(cnt, 0.04 * peri, False)
if len(approx) > 4 and cv2.contourArea(cnt) <= 3000 and cv2.contourArea(cnt) >= 100:
shape = "circle"
else:
shape = "veins"
if(shape=="circle"):
cv2.drawContours(xmask, [cnt], -1, 0, -1)
finimage = cv2.bitwise_and(fundus_eroded,fundus_eroded,mask=xmask)
blood_vessels = cv2.bitwise_not(finimage)
dilated = cv2.erode(blood_vessels, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(7,7)), iterations=1)
#dilated1 = cv2.dilate(blood_vessels, cv2.getStructuringElement(cv2.MORPH_ELLIPSE,(3,3)), iterations=1)
blood_vessels_1 = cv2.bitwise_not(dilated)
return blood_vessels_1
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