plegendrepolynomialfitting

Approximates image to flat background using Legendre polynomial fitting.

Synopsis

plegendrepolynomialfitting xorder yorder [im_in|-] [im_mk|-] [im_out|-]

Description

plegendrepolynomialfitting converts an image content into a flat background image, using Legendre polynomial. It uses the orthogonality relation of the Legendre polynomials to expand an image as a double sum of those functions. The sum is then evaluated to produce an image that approximates a projection onto the space of polynomial images.

This operator removes all sorts of uneven illumination with a gradually change of background color raising or falling from any part of a border to the opposite border.

Parameters

xorder is the x order [0..10].
yorder is the y order [0..10].

Order values control the precision of the background fitting: the greater the order values, the closer to the input image content.

Inputs

im_in: a 2D image.

Outputs

im_out: a 2D image of the same type as the input image.

Result

Returns SUCCESS or FAILURE.

Examples

Correction the illumination of the tangram image using background subtraction. The background is approximated by linear regression:

   plegendrepolynomialfitting 2 2 tangram.pan a.pan
   psub tangram.pan a.pan b.pan
   pmeanvalue a.pan; mean=`pstatus`
   paddcst $mean b.pan out.pan

More examples

C++ Prototype

Errc PLegendrePolynomialFitting( const Img2duc &im_in, Img2duc &im_out, int yOrder, int yOrder );

Version française

Calcul de l'approximation du fond d'une image en utilisant une approximation par polynômes de Legendre.

Author: Régis Clouard