[FRAMES, DESCRS] = VL_PHOW(IM) extracts PHOW features from the image IM. This function is a wrapper around VL_DSIFT() and VL_IMSMOOTH().
The PHOW descriptors where introduced in [1]. By default, VL_PHOW() computes the gray-scale variant of the descriptor. The COLOR option can be used to compute the color variant instead.
Set to true to turn on verbose output.
Scales at which the dense SIFT features are extracted. Each value is used as bin size for the VL_DSIFT() function.
Set to false to turn off the fast SIFT features computation by VL_DSIFT().
Step (in pixels) of the grid at which the dense SIFT features are extracted.
Choose between GRAY (PHOW-gray), RGB, HSV, and OPPONENT (PHOW-color).
Contrast threshold below which SIFT features are mapped to zero. The input image is scaled to have intensity range in [0,1] (rather than [0,255]) and this value is compared to the descriptor norm as returned by VL_DSIFT().
Size of the Gaussian window in units of spatial bins.
The image is smoothed by a Gaussian kernel of standard deviation SIZE / MAGNIF.
If set to TRUE, the descriptors are returned in floating point format.