  High fidelity reproductions of paintings provide new opportunities to museums
in preserving and providing access to cultural heritage. This paper presents an
integrated system which is able to capture and fabricate color, topography and
gloss of a painting, of which gloss capturing forms the most important
contribution. A 3D imaging system, using fringe-encoded stereo imaging, is
extended to capture spatially-varying gloss, utilizing specular reflectance
polarization. The gloss is measured by sampling the specular reflection around
Brewster's angle, where these reflections are effectively polarized, and can be
separated from the unpolarized, diffuse reflectance. Off-center gloss
measurements are calibrated relative to the center measurement. Off-specular
gloss measurements, following from local variation of the surface normal, are
masked based on the height map and corrected. Shadowed regions, caused by the
3D relief, are treated similarly. The area of a single capture is approximately
180x90mm at a resolution of 25x25micron. Aligned color, height, and gloss tiles
are stitched together, registering overlapping color areas. These maps are
inputs for a 3D printer. Two paintings were reproduced to verify the
effectiveness and efficiency of the proposed system. One painting was scanned
four times, consecutively rotated by 90 degrees, to evaluate the influence of
the scanning system geometric configuration on the gloss measurement.
Experimental results show that the method is sufficiently fast for practical
application. The results can well be used for the purpose of physical
reproduction and other applications needing first-order estimates of the
appearance. Our method to extend appearance scanning with gloss measurements is
a valuable addition in the quest for realistic reproductions, in terms of its
practical applicability and its perceptual added value, when added to color and
topography.
