I want to draw a bounding box around each closed contour of an area larger than some threshold, not just the biggest contour. How can I go about doing this? So far this is what I have tried:
contours, _ = cv2.findContours(thresh, cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
for c in contours:
rect = cv2.boundingRect(c)
if rect[2] < 100 or rect[3] < 100: continue
print cv2.contourArea(c)
x,y,w,h = cv2.boundingRect(c)
cv2.rectangle(im,(x,y),(x+w,y+h),(0,255,0),2)
cv2.putText(im,'Moth Detected',(x+w+10,y+h),0,0.3,(0,255,0))
cv2.imshow("Show",im)
cv2.waitKey()
cv2.destroyAllWindows()
Remember, your indentation level matters in Python. It's also worth noting that your code doesn't necessarily draw a box around the largest contour, it draws a box around the last element of contours
. Fortunately, the fix is simple. You just need to indent your calls to cv2.rectangle()
and cv2.putText()
so they evaluate on every loop iteration. You can also eliminate a call to cv2.boundingRect()
by expanding rect
into x,y,w,h
. Your code would then be:
contours, _ = cv2.findContours(thresh, cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)
for c in contours:
rect = cv2.boundingRect(c)
if rect[2] < 100 or rect[3] < 100: continue
print cv2.contourArea(c)
x,y,w,h = rect
cv2.rectangle(im,(x,y),(x+w,y+h),(0,255,0),2)
cv2.putText(im,'Moth Detected',(x+w+10,y+h),0,0.3,(0,255,0))
cv2.imshow("Show",im)
cv2.waitKey()
cv2.destroyAllWindows()
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