NAME: CORRMAT_ANALYZE PURPOSE: Find the optimal (x,y) offset to maximize correlation of 2 images EXPLANATION: Analyzes the 2-D cross-correlation function of two images and finds the optimal(x,y) pixel offsets. Intended for use with function CORREL_IMAGES. CALLING SEQUENCE: corrmat_analyze, correl_mat, xoffset_optimum, yoffset_optimum, max_corr, edge, plateau, [XOFF_INIT=, YOFF_INIT=, REDUCTION=, MAGNIFICATION=, PLATEAU_THRESH=, /PRINT] INPUTS: correl_mat = the cross-correlation matrix of 2 images. (as computed by function CORREL_IMAGES( imA, imB ) ). NOTE: If correl_mat(*,*,1) is the number of pixels for each correlation, (the case when /NUMPIX was specified in call to CORREL_IMAGES) then sqrt( sqrt( # pixels )) is used as correlation weighting factor. OPTIONAL INPUT KEYWORDS: XOFF_INIT = initial X pixel offset of image_B relative to image_A. YOFF_INIT = Y pixel offset, (both as specified to correl_images). REDUCTION = reduction factor used in call to CORREL_IMAGES. MAGNIFICATION = magnification factor used in call to CORREL_IMAGES, this allows determination of offsets up to fractions of a pixel. PLATEAU_THRESH = threshold used for detecting plateaus in the cross-correlation matrix near maximum, (default=0.01), used only if MAGNIFICATION > 1 /PRINT causes the result of analysis to be printed. OUTPUTS: xoffset_optimum = optimal X pixel offset of image_B relative to image_A. yoffset_optimum = optimal Y pixel offset. max_corr = the maximal correlation corresponding to optimal offset. edge = 1 if maximum is at edge of correlation domain, otherwise=0. plateau = 1 if maximum is in a plateau of correlation function, else=0. PROCEDURE: Find point of maximum cross-correlation and calc. corresponding offsets. If MAGNIFICATION > 1: the correl_mat is checked for plateau near maximum, and if found, the center of plateau is taken as point of maximum cross-correlation. MODIFICATION HISTORY: Written, July-1991, Frank Varosi, STX @ NASA/GSFC Use ROUND instead of NINT, June 1995 Wayne Landsman HSTX Remove use of non-standard !DEBUG system variable W.L. HSTX Converted to IDL V5.0 W. Landsman September 1997