generic-library/opencv
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Merge pull request #2313 from m3d:patch-1

Browse Source
This commit is contained in:
Roman Donchenko 2014-02-11 17:10:22 +04:00 committed by OpenCV Buildbot
commit 1cef6f9fb1
1 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
doc/py_tutorials/py_imgproc/py_contours/py_contours_begin/py_contours_begin.rst
View File

@ -28,9 +28,9 @@ Let's see how to find contours of a binary image:
im = cv2.imread('test.jpg')
imgray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)
ret,thresh = cv2.threshold(imgray,127,255,0)
image, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
contours, hierarchy = cv2.findContours(thresh,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)
See, there are three arguments in **cv2.findContours()** function, first one is source image, second is contour retrieval mode, third is contour approximation method. And it outputs the image, contours and hierarchy. ``contours`` is a Python list of all the contours in the image. Each individual contour is a Numpy array of (x,y) coordinates of boundary points of the object.
See, there are three arguments in **cv2.findContours()** function, first one is source image, second is contour retrieval mode, third is contour approximation method. And it outputs the contours and hierarchy. ``contours`` is a Python list of all the contours in the image. Each individual contour is a Numpy array of (x,y) coordinates of boundary points of the object.
.. note:: We will discuss second and third arguments and about hierarchy in details later. Until then, the values given to them in code sample will work fine for all images.
@ -43,18 +43,18 @@ To draw the contours, ``cv2.drawContours`` function is used. It can also be used
To draw all the contours in an image:
::
img = cv2.drawContour(img, contours, -1, (0,255,0), 3)
cv2.drawContours(img, contours, -1, (0,255,0), 3)
To draw an individual contour, say 4th contour:
::
img = cv2.drawContours(img, contours, 3, (0,255,0), 3)
cv2.drawContours(img, contours, 3, (0,255,0), 3)
But most of the time, below method will be useful:
::
cnt = contours[4]
img = cv2.drawContours(img, [cnt], 0, (0,255,0), 3)
cv2.drawContours(img, [cnt], 0, (0,255,0), 3)
.. note:: Last two methods are same, but when you go forward, you will see last one is more useful.