[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 false
Set to true to compute PHOW-color rather than PHOW-gray.
- 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.