On the Utility of Spectral-Maximum- Based Automated Thread Counting from X-Radiographs of Paintings on Canvas

Manual thread counting is possible from the weave pattern visible at sufficient enlargement of the intensity pattern in an X-radiograph of a painting on canvas. a recently introduced algorithm [1] for automated thread counting relies upon the topography of the twodimensional Fourier transform of the X-radiograph. (For a description of the two-dimensional Fourier transform see the appendix.) a procedure based on a two-dimensional Fourier transform is at the heart of ongoing automated thread counting campaigns among paintings by van gogh, vermeer and the delft School, Matisse, renoir, Monet and gauguin. in combination with knowledge of the artist’s studio practice, such as van gogh’s rapid usage of rolls of pre-primed canvas during his late French period, thread count data can be used to assist in art historical issues such as dating and authentication. this paper presents the results of a number of numerical exper iments intended to elaborate on This paper establishes that the two-dimensional Fourier transform, spectral-maximum-based extraction of thread density appears suited to automatic thread counting from scanned X-radiographs of paintings for a range of European painters from the seventeenth century to the early twentieth century. With regularly woven canvas, striping occurring in color-coded maps of local thread count can be used to identify rollmate candidates originally separated by as much as a few meters, maybe more. These results suggest that recently developed spectral-maximum-based thread counting algorithms are sufficiently sophisticated to support major efforts in archival thread counting as key forensic data in a variety of art historical investigations. Still, the canvas and priming used by some artists require a more refined approach to automated thread counting than a simple spectral-maximum-based scheme.