IM=VLPATTERN(NAME) returns an instance of the specified pattern. These stock patterns are useful for testing algoirthms.

All generated patterns are returned as an image of class DOUBLE. Both gray-scale and colour images have range in [0,1].

VL_IMPATTERN() without arguments shows a gallery of the stock patterns. The following patterns are supported:

Wedge

  The image of a wedge.

Cone

  The image of a cone.

SmoothChecker

  A checkerboard with Gaussian filtering on top. Use the option-value pair 'sigma', SIGMA to specify the standard deviation of the smoothing and the pair 'step', STEP to specfity the checker size in pixels.

ThreeDotsSquare

  A pattern with three small dots and two squares.

UniformNoise

  Random i.i.d. noise.

Blobs:

      Gaussian blobs of various sizes and anisotropies.

Blobs1:

      Gaussian blobs of various orientations and anisotropies.

Blob:

      One Gaussian blob. Use the option-value pairs 'sigma',
      'orientation', and 'anisotropy' to specify the respective
      parameters. 'sigma' is the scalar standard deviation of an
      isotropic blob (the image domain is the rectangle
      [-1,1]^2). 'orientation' is the clockwise rotation (as the Y
      axis points downards). 'anisotropy' (>= 1) is the ratio of the
      the largest over the smallest axis of the blob (the smallest
      axis length is set by 'sigma'). Set 'cut' to TRUE to cut half
      half of the blob.

A stock image

  Any of 'box', 'roofs1', 'roofs2', 'river1', 'river2', 'spotted'.

All pattern accept a SIZE parameter [WIDTH,HEIGHT]. For all but the stock images, the default size is [128,128].