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

fixed some more compile errors and test failures

Browse Source
This commit is contained in:
Vadim Pisarevsky
2014-10-17 14:22:02 +04:00
parent d36b546df8
commit 1176d4ef84
16 changed files with 165 additions and 136 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
doc/user_guide/ug_features2d.rst
View File

@@ -65,18 +65,18 @@ Let us break the code down. ::
We load two images and check if they are loaded correctly.::
// detecting keypoints
FastFeatureDetector detector(15);
Ptr<FeatureDetector> detector = FastFeatureDetector::create(15);
vector<KeyPoint> keypoints1, keypoints2;
detector.detect(img1, keypoints1);
detector.detect(img2, keypoints2);
detector->detect(img1, keypoints1);
detector->detect(img2, keypoints2);
First, we create an instance of a keypoint detector. All detectors inherit the abstract ``FeatureDetector`` interface, but the constructors are algorithm-dependent. The first argument to each detector usually controls the balance between the amount of keypoints and their stability. The range of values is different for different detectors (For instance, *FAST* threshold has the meaning of pixel intensity difference and usually varies in the region *[0,40]*. *SURF* threshold is applied to a Hessian of an image and usually takes on values larger than *100*), so use defaults in case of doubt. ::
// computing descriptors
SurfDescriptorExtractor extractor;
Ptr<SURF> extractor = SURF::create();
Mat descriptors1, descriptors2;
extractor.compute(img1, keypoints1, descriptors1);
extractor.compute(img2, keypoints2, descriptors2);
extractor->compute(img1, keypoints1, descriptors1);
extractor->compute(img2, keypoints2, descriptors2);
We create an instance of descriptor extractor. The most of OpenCV descriptors inherit ``DescriptorExtractor`` abstract interface. Then we compute descriptors for each of the keypoints. The output ``Mat`` of the ``DescriptorExtractor::compute`` method contains a descriptor in a row *i* for each *i*-th keypoint. Note that the method can modify the keypoints vector by removing the keypoints such that a descriptor for them is not defined (usually these are the keypoints near image border). The method makes sure that the ouptut keypoints and descriptors are consistent with each other (so that the number of keypoints is equal to the descriptors row count). ::