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[英]Opencv python lane detection draw line using cv2.line() change line color bug unsuccessfully
[英]Python OpenCV: Conversion from float to int for using cv2.line()
我正在使用Python 2.7和OpenCV 3.1.0開發openCV的光流教程,並且有一個關於使用cv2.line()的問題。 以下是帶有突出顯示部分的原始代碼:
import numpy as np
import cv2
cap = cv2.VideoCapture('slow.flv')
# params for ShiTomasi corner detection
feature_params = dict( maxCorners = 100,
qualityLevel = 0.3,
minDistance = 7,
blockSize = 7 )
# Parameters for lucas kanade optical flow
lk_params = dict( winSize = (15,15),
maxLevel = 2,
criteria = (cv2.TERM_CRITERIA_EPS | cv2.TERM_CRITERIA_COUNT, 10, 0.03))
# Create some random colors
color = np.random.randint(0,255,(100,3))
# Take first frame and find corners in it
ret, old_frame = cap.read()
old_gray = cv2.cvtColor(old_frame, cv2.COLOR_BGR2GRAY)
p0 = cv2.goodFeaturesToTrack(old_gray, mask = None, **feature_params)
# Create a mask image for drawing purposes
mask = np.zeros_like(old_frame)
while(1):
ret,frame = cap.read()
frame_gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
# calculate optical flow
p1, st, err = cv2.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, None, **lk_params)
# Select good points
good_new = p1[st==1]
good_old = p0[st==1]
################## IMPORTANT ##################
# draw the tracks
for i,(new,old) in enumerate(zip(good_new,good_old)):
a,b = new.ravel()
c,d = old.ravel()
mask = cv2.line(mask, (a,b),(c,d), color[i].tolist(), 2)
frame = cv2.circle(frame,(a,b),5,color[i].tolist(),-1)
################## IMPORTANT ##################
########### START insert code below ###########
# Mean-vector of camera movement
############ END insert code below ############
img = cv2.add(frame,mask)
cv2.imshow('frame',img)
k = cv2.waitKey(30) & 0xff
if k == 27:
break
# Now update the previous frame and previous points
old_gray = frame_gray.copy()
p0 = good_new.reshape(-1,1,2)
cv2.destroyAllWindows()
cap.release()
在我的工作空間中,變量a,b,c和d顯示為array scalar float32
。 所以我認為,為了執行cv2.line()或cv2.circle(),需要將它們轉換為int的元組。
當我嘗試使用cv2.line()添加代碼時,我必須使用轉換為int(見下文),否則我收到一條非常明確的消息: TypeError: integer argument expected, got float
###################### START added code
ofvec = p1 - p0
ofvec = np.mean(ofvec, 1) # Collapse the first dimension
ofvec_cam = np.mean(ofvec,0) # mean of camera movement
height, width = old_frame.shape[:2]
x0 = np.int(width/2)
y0 = np.int(height/2)
pt_center = (x0, y0)
x = np.int( x0 - ofvec_cam[0].tolist() )
y = np.int( y0 - ofvec_cam[1].tolist() )
pt_ofvec_cam = (x, y)
frame = cv2.line(frame, pt_center, pt_ofvec_cam, [0, 0, 255], 2)
###################### END added code
任何人都可以向我解釋這個差異嗎? 在此先感謝您,祝您度過愉快的一天! AMTQ
似乎cv2.line()對待兩種類型的浮動:“標准”Python浮動和numpy浮動。 請參閱使用Python 2.7和OpenCV 3.1.0的最低工作示例:
import numpy as np, cv2
mask = np.zeros([10, 20, 3], dtype=np.uint8)
color = [0, 0, 0]
# Using Numpy
a = np.float32(12.34)
mask = cv2.line(mask, (a,a), (a,a), color)
# Using standard Python data type
b = 12.34
mask = cv2.line(mask, (b,b), (b,b), color)
如果命令執行沒有故障,如果b我們發現上述錯誤:
in <module> mask = cv2.line(mask, (b,b), (b,b), color)
TypeError: integer argument expected, got float`
關於最初的問題,我確認在OpenCV教程中,變量a,b,c和d都是numpy-float,而在添加的代碼中,變量x和y是標准Python浮點數,然后由np轉換為numpy-ints。 INT()。
兩種數據類型都提供了一個方法__int__()
,它返回float的int值(另請參見native int類型和numpy int類型之間的區別 )。
我發現的唯一提到的是關於OpenCV 2.4.13文檔中的方法fromarray的注釋:
注意在新的Python包裝器(cv2模塊)中,不需要該函數,因為cv2可以處理Numpy數組(這是唯一受支持的數組類型)。
在OpenCV 3.1.0的文檔中,方法fromarray
不再存在。
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