del2_5pt.m

基于matlab的反演程序,用于地球物理勘探中射线追踪及偏移成像程序.

function [output]=del2_5pt(input,delx)
% DEL2_5PT ... compute the 5 point Laplacian
%
% [output]=del2_5pt(input,delx)
%
% DEL2_5PT computes the 5 point approximation to the laplacian operator of 
% the two dimensional matrix 'input'.  The horizontal and vertical bin
% spacing of the matrix MUST be the same.    
%
% input = input matrix
% delx = the horizontal/ vertical bin spacing in consistent units
%
% output = the output matrix
%
% by Carris Youzwishen, April 1999
%
% NOTE: It is illegal for you to use this software for a purpose other
% than non-profit education or research UNLESS you are employed by a CREWES
% Project sponsor. By using this software, you are agreeing to the terms
% detailed in this software's Matlab source file.
 
% BEGIN TERMS OF USE LICENSE
%
% This SOFTWARE is maintained by the CREWES Project at the Department
% of Geology and Geophysics of the University of Calgary, Calgary,
% Alberta, Canada.  The copyright and ownership is jointly held by 
% its author (identified above) and the CREWES Project.  The CREWES 
% project may be contacted via email at:  [e-mail]
% 
% The term 'SOFTWARE' refers to the Matlab source code, translations to
% any other computer language, or object code
%
% Terms of use of this SOFTWARE
%
% 1) Use of this SOFTWARE by any for-profit commercial organization is
%    expressly forbidden unless said organization is a CREWES Project
%    Sponsor.
%
% 2) A CREWES Project sponsor may use this SOFTWARE under the terms of the 
%    CREWES Project Sponsorship agreement.
%
% 3) A student or employee of a non-profit educational institution may 
%    use this SOFTWARE subject to the following terms and conditions:
%    - this SOFTWARE is for teaching or research purposes only.
%    - this SOFTWARE may be distributed to other students or researchers 
%      provided that these license terms are included.
%    - reselling the SOFTWARE, or including it or any portion of it, in any
%      software that will be resold is expressly forbidden.
%    - transfering the SOFTWARE in any form to a commercial firm or any 
%      other for-profit organization is expressly forbidden.
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% END TERMS OF USE LICENSE

[nrows,ncolumns]=size(input);

input2=zeros(nrows+2,ncolumns+2);
input2(2:nrows+1,2:ncolumns+1)=input;
factor=1/(delx^2);
clear input


% for first dimension

   output = (input2(3:nrows+2,2:ncolumns+1) - 2.*input2(2:nrows+1,2:ncolumns+1) +...
                  input2(1:nrows,2:ncolumns+1))*factor;

% for second dimension 

 output = (input2(2:nrows+1,3:ncolumns+2) - 2.*input2(2:nrows+1,2:ncolumns+1) +...
                 input2(2:nrows+1,1:ncolumns))*factor+ output;