Fondamentalmente, si utilizza la funzione findContours
, in combinazione con molte altre funzioni che OpenCV offre in particolare per questo scopo.
Funzioni utili utilizzati (sorpresa, sorpresa, si tutte appaiono sulla pagina Structural Analysis and Shape Descriptors in OpenCV Docs):
codice di esempio (ho tutti gli oggetti di di regionprops
tranne WeightedCentroid
e EulerNumber
Matlab - si potrebbe lavorare fuori EulerNumber
utilizzando cv2.RETR_TREE
in findContours
e guardando la gerarchia risultante e sono sicuro che lo WeightedCentroid
non sarebbe poi così difficile.
# grab contours
cs,_ = cv2.findContours(BW.astype('uint8'), mode=cv2.RETR_LIST,
method=cv2.CHAIN_APPROX_SIMPLE)
# set up the 'FilledImage' bit of regionprops.
filledI = np.zeros(BW.shape[0:2]).astype('uint8')
# set up the 'ConvexImage' bit of regionprops.
convexI = np.zeros(BW.shape[0:2]).astype('uint8')
# for each contour c in cs:
# will demonstrate with cs[0] but you could use a loop.
i=0
c = cs[i]
# calculate some things useful later:
m = cv2.moments(c)
# ** regionprops **
Area = m['m00']
Perimeter = cv2.arcLength(c,True)
# bounding box: x,y,width,height
BoundingBox = cv2.boundingRect(c)
# centroid = m10/m00, m01/m00 (x,y)
Centroid = (m['m10']/m['m00'],m['m01']/m['m00'])
# EquivDiameter: diameter of circle with same area as region
EquivDiameter = np.sqrt(4*Area/np.pi)
# Extent: ratio of area of region to area of bounding box
Extent = Area/(BoundingBox[2]*BoundingBox[3])
# FilledImage: draw the region on in white
cv2.drawContours(filledI, cs, i, color=255, thickness=-1)
# calculate indices of that region..
regionMask = (filledI==255)
# FilledArea: number of pixels filled in FilledImage
FilledArea = np.sum(regionMask)
# PixelIdxList : indices of region.
# (np.array of xvals, np.array of yvals)
PixelIdxList = regionMask.nonzero()
# CONVEX HULL stuff
# convex hull vertices
ConvexHull = cv2.convexHull(c)
ConvexArea = cv2.contourArea(ConvexHull)
# Solidity := Area/ConvexArea
Solidity = Area/ConvexArea
# convexImage -- draw on convexI
cv2.drawContours(convexI, [ConvexHull], -1,
color=255, thickness=-1)
# ELLIPSE - determine best-fitting ellipse.
centre,axes,angle = cv2.fitEllipse(c)
MAJ = np.argmax(axes) # this is MAJor axis, 1 or 0
MIN = 1-MAJ # 0 or 1, minor axis
# Note: axes length is 2*radius in that dimension
MajorAxisLength = axes[MAJ]
MinorAxisLength = axes[MIN]
Eccentricity = np.sqrt(1-(axes[MIN]/axes[MAJ])**2)
Orientation = angle
EllipseCentre = centre # x,y
# ** if an image is supplied with the BW:
# Max/Min Intensity (only meaningful for a one-channel img..)
MaxIntensity = np.max(img[regionMask])
MinIntensity = np.min(img[regionMask])
# Mean Intensity
MeanIntensity = np.mean(img[regionMask],axis=0)
# pixel values
PixelValues = img[regionMask]
fonte
2012-01-30 05:14:26
+1 per La parola chiave "regionprops" che mi ha salvato ore di googling – Tarrasch