Documentaton - BLOCKS - BLOCK_FEAT

This block extracts features from images in a database.

BK = BLOCK_DICTIONARY() Initializes the block with the default options.

BK = BLOCK_DICTIONARY(BK) Executes the block with options and inputs BK.

Required Inputs:

db

The database to extract features from. All segments will be processed.

Options:

bk.rand_seed

Set the random seed. Default is [], which does not change the random seed.

bk.detector

The type of feature detector to use. Default 'sift'. Valid types are: sift: Standard SIFT detector (DoG) from VLFeat. ipld: Harris multiscale + DoG (IPLD implementation). iplddog: The DoG from the IPLD implementation. dsift: Dense SIFT. Only compatible with dsift descriptor. dsift-color: Same as dsift. Only compatible with dsift-color

              descriptor.
bk.descriptor

The type of feature descriptor to use. Default 'sift'. Valid types are: sift: Standard SIFT descriptor from VLFeat. siftnosmooth: Standard SIFT descriptor which ommits smoothing. ipld: Standard SIFT descriptor (IPLD implementation). dsift: Dense SIFT descriptor. dsift-color: Dense color SIFT descriptor

bk.ref_size

Resize images to have their longest side equal to this number before processing. Default of [] means leave the images unmodified.

bk.min_sigma

Throw away detected features whose frame size is less than min_sigma. Frame size is relative to the ref_size of the image.

bk.max_num

A limit on how many features are extracted. Default +inf.

bk.rescale

Descriptors are computed on regions whose radius is rescale times the scale sigma of the frame. For the standard sift descriptor, for instance, rescale is two times the magnification paramter of the descriptor. Default 6.

DSIFT and DSIFT-COLOR Options:

bk.dsift_size:

  The size of a spatial bin in dsift. For example, 3 will create a
  descriptor which is 12x12 pixels. This option is required when
  using this descriptor.

bk.dsift_step:

  The step size in pixels between descriptors. 1 produces a
  descriptor for every pixel of the image. This option is required
  when using this descriptor.

DSIFT-COLOR Options:

bk.dsift_minnorm:

  Discard descriptors whose norm is less than dsift_minnorm in
  both the red and green channels.