[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.
- Verbose [false]
Set to true to turn on verbose output.
- Sizes [[4 6 8 10]]
Scales at which the dense SIFT features are extracted. Each value is used as bin size for the VL_DSIFT() function.
- Fast [true]
Set to false to turn off the fast SIFT features computation by VL_DSIFT().
- Step [2]
Step (in pixels) of the grid at which the dense SIFT features are extracted.
- Color [GRAY]
Choose between GRAY (PHOW-gray), RGB, HSV, and OPPONENT (PHOW-color).
- ContrastThreshold [0.005]
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().
- WindowSize [1.5]
Size of the Gaussian window in units of spatial bins.
- Magnif [6]
The image is smoothed by a Gaussian kernel of standard deviation SIZE / MAGNIF.
- FloatDescriptors [false]
If set to TRUE, the descriptors are returned in floating point format.