Learning OpenCV, 2nd Edition

cv::RETR_TREE

Retrieves all the contours and reconstructs the full hierarchy of nested contours. In our example

(

Figure 8-1 and

Figure 8-2), this means that the root node is the outermost contour c0. Below c0 is the hole h00, which

is connected to the other hole h01 at the same level. Each of those holes in turn has children (the

contours c000 and c010, respectively), which are connected to their parents by vertical links. Thi

h become the leaf nodes in the tree.

s

ontours in the image, whic

The next five values pertain to the method (i.e., how the contours are represented):

continues down to the most-interior c

cv:

ce a large number

point. No attempt is made to

ny

ction of the number of points returned. The extreme

that is oriented along the x-y axes. In this case, only four

AIN_APPROX_TC89_L1 or cv::CHAIN_APPROX_TC89_KCOS

returned.

T-C algorithm requires no additional parameters to run.

t. The offset argument is optional. If

void cv::drawContours(

:CHAIN_APPROX_NONE

Translates all the points from the contour code into points. This operation

oints, as each point will be one of the eight neighbors of the previous

will produ

of p

reduce the number of vertices returned.

cv::CHAIN_APPROX_SIMPLE

Compresses horizontal, vertical, and diagonal segments, leaving only their ending points. ...