scene sketch – color drawings
hand drawing reflecting an image scene by color, sketch is more a cartoon-like drawing
Extract a multi-resolution wavelet fingerprint of the complete image comparing color and shape. 20 compression coefficients allows efficient retrieval.
shape sketch – line drawings
this kind of hand drawings provide the most natural extension of a language based word-level query, which is just a rough outline of an object focusing entirely on the shape.
- Sketch is a thin line drawing focusing on shape, no appearance info, may contain one to many line stokes, define a valuable stroke point ordering.
- Contour is a connected sequence of points, which may come from the input sketch
- Contour fragment is a connected subset of a contour. an ordered list of points
- Chord is a line joining two points of a region boundary, some could be used as shape descriptor:
- histogram of distribution of chord lengths and angels
- relative orientations between specifically chosen chords
- used in Geometric hashing
user stroke and image edges may be over fragmented, and broken into multiple contours- so partial matching, e.g. The PArtial Contour and Efficient Matching (PACEM)
efficient image retrieval in large database by modeling object of interest using a sketch of the object shape.
a bag of local fragment codewords, which are fragment prototypes that are obtained from edges in image database.
use these fragment shape(codewords) to describe both the sketch query and images
painting as query
it is limited by perceptual error in both shape and color, as well as by the artistic prowess and patience of the user.
similar to the Fourier transform, but encodes both frequency and spacial information.
most used in area of image compression – saving the few largest wavelet coefficients for an image, throwing away all of the smaller coefficients, it is possible to recover a fairly accurate representation of image.
20 coeffs 100 coeffs 400 coeffs Original (16,000 coeffs)
by collecting 20 coefficients for each color channel, we distill a small signature for each of these images, save these signature and