On Sun, 29 Mar 2009 17:22:47 -0700 Fred Weinhaus <[email protected]> wrote:
| | | >The program is not available anymore and I do not have a copy. | >I believe it is used more for photo scanning of documents and books | >rather than real world images at a longer distance. | > | >However taking a straight on photo of a picket fence or equally spaced | >houses, should be able to produce a similar set of lines. Though one | >which an automatic coordinate extraction program would not be able to | >directly handle. | > | >But I understand how the program works in automatically finding the | >line crossings of the equally spaced parallel lines, and once it has | >determined those coordinates the rest is much like your spread sheet | >but with far more coordinates, spread over a larger radial range. | > | >That allows for better matching by least squares function fitting. | >Something IM already does for handing large numbers of 'control | >points' than the minimum needed for affine, perspective, or (still | >undocumented) polynomial distortions, in pixel coordinates. | > | > | >FYI Polynomial Distortion | > -distort polynomial 'order, coordinate-pairs, ....' | >Where order is largest X or Y power of for the polynomial | >and determines the minimum number of coordinates needed | > order function minimum coodinates | > 0 constant 1 | > 1 affine 3 | > 1.5 bilinear 4 | > 2 quadratic 6 | > 3 cubic 10 | > 4 quartic 15 | > 5 quintic 21 | > | >For example a cubic distortion (order 3) | >distorts the image using the reverse mapping function | > Xsrc = a0 + a1*x + a2*y # affine terms | > + a3*x*y # bi-linear term | > + a4*x^2 + a5*y^2 # quadratic terms | > + a6*x^3 + a7*x^2*y + a8*x*y^2 + a9*y^3 # cubic terms | > | >and a similar but completely separate Y coordinate mapping function. | > | | | Anthony, | | Currently your least squares fit only works with X,Y coordinate to | fit an X equation and a Y equation. I am not sure you have anything | that will work directly with fitting a single polynomial in | R=sqrt(X^2+Y^2). Or do you? | I was thinking of extracting coordinates in terms of radii, then feeding them into the polynomial just a X coordinates, so as to get the verbose best fit polynomial X formula. Then the parameters can be scaled appropriately for their order to get the barrel parameters. It is an Idea, but I need an image of parallel lines to try out. Anthony Thyssen ( System Programmer ) <[email protected]> ----------------------------------------------------------------------------- The better the monkeys got at answering those questions, the more baffling the universe became; knowledge increases ignorance. -- Terry Pratchett, "The Science of Diskworld" ----------------------------------------------------------------------------- Anthony's Home is his Castle http://www.cit.gu.edu.au/~anthony/ _______________________________________________ Magick-users mailing list [email protected] http://studio.imagemagick.org/mailman/listinfo/magick-users
