Examples


First steps - Tutorial

  1. Take a a gray level image of yours (e.g. a.pgm)
  2. Interest Point Detection (with Harris-Laplace):
    Detect -dt har a.pgm a.har

    Note: if you use -affine detection also specify -angles

  3. Compute local descriptors for each interest point (based on sift)
    ComputeDescriptor a.pgm a.har a.har.sift

  4. Show result of (2) on the image:
    DrawCorners -col y -wi 2 a.pgm a.har a.har.pnm

  5. Dump the result of (3) to a text
    dumpcontents a.har.sift > a.txt

  6. Dump only the computed descriptors (of step (3)) to a text
    corners2text a.har.sift -adddesc a.har.desc.txt

  7. Convert the results to MatLab format:
    corners2matlab a.har.sift a.mat


Detection with a list of images

  1. Create a file called images.lst. Each line should contain a name of an image.
  2. Detect interest points based on Laplace-of-Gaussian.
    Detect -dtype log @images.lst result.log

  3. Apply affine and rotation invariance for each point and compute SIFT descriptors. (the next two lines should be typed in one!)
    ComputeDescriptor -dt sift -aff -an @images.lst result.log  
    result.log.sift

  4. Draw the detection results (with affine estimation) on the 3rd image in the list.
    SelectCorners -fid 2 result.log.sift third.sift  
    DrawCorners -color yellow @images.lst third.sift third.pnm

    Note that first we have to select the points of the third image to a different file (fid==2, because the files are numbered from 0), then we can use DrawCorners with the list file, it will load up the correct image.

  5. Show the same patches but now extracted in a thumbnail format.
    DrawCorners -th_on -co ye @images.lst third.sift third_th.pnm


Examples for SelectCorners

Select interest points that have the pixel (20,10) included in their interest region:
SelectCorners -x 20 -y 10 source.har dest.har

Select 10 random interest point:

SelectCorners -random 10 source.har dest.har

Select interest points having scale between 2 and 10:

SelectCorners -scmin 2 source.har tmp.har  
SelectCorners -scmax 10 tmp.har dest.har

Select the 10th interest point:

SelectCorners -numb 9 source.har dest.har

Select the 10th and 20th interest points:

SelectCorners -numb ’9 19’ source.har dest.har

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