By default, pictures are divided in 9 x 9 blocks.
value, and it can be changed with
For large databases, for complex images, for images with a lot of text or
for sets of near-similar images, it might be better to raise that value to
However, raising that value obviously means that vectors will require more
value should remain the same in order to get comparable vectors. So if you
(for instance), you should always use that value for all pictures you will
compute a digest for.
The average intensity of each block is based upon a small centered zone.
The "p ratio" determines the size of that zone. The default is 2.0, and that
ratio mimics the behavior that is described in the reference algorithm.
For very specific cases (complex images) or if you get too many false
positives, as an alternative to increasing lambdas, you can try to lower that
value, for instance to 1.5.
The lowest acceptable value is 1.0.
By default, featureless borders of the original image are ignored. The size
of each border depends on the sum of absolute values of differences between
adjacent pixels, relative to the total sum.
That feature can be disabled with
Any other value will enable it.
changes the tolerance. The default value is 5. Less shaves less, more shaves
This is a safe-guard against unwanted excessive auto-cropping.
The default (0.25) means that no more than 25% of the total width (or
height) will ever be shaved.