% @(#)align_imag.hlq 17.1.1.1 (ESO-DMD) 01/25/02 17:43:15 %++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ %.COPYRIGHT (c) 1990 European Southern Observatory %.IDENT align_imag.hlq %.AUTHOR KB, IPG/ESO %.KEYWORDS MIDAS, help files, ALIGN/IMAGE %.PURPOSE On-line help file for the command: ALIGN/IMAGE %.VERSION 1.0 03-JUNE-1986 : Creation, KB %---------------------------------------------------------------- \se SECTION./IMAG \es\co ALIGN/IMAGE 17-OCT-2001 KB \oc\su ALIGN/IMAGE intab reftab [option] [overlay_flag] [residual_flag] compute transformation coefficients for two rotated images \us\pu Purpose: Compute transformation coefficients for rotation translation and scaling of an image. \\ The coefficients are computed using two tables with columns of world coordinates of common objects in the image to be aligned and the reference image, respectively. \up\sub Subject: Alignment, Transformation, Superposition \bus\sy Syntax: ALIGN/IMAGE intab reftab [option] [overlay_flag] [residual_flag] \ys\pa intab = name of table and columns with world coordinates of object in the image to be aligned in the form: table[,:xlabel,:ylabel] \\ If the labels are omitted, they are defaulted to label :XCEN and :YCEN which are created by the Midas commands CENTER/GAUSS or CENTER/MOMENT \ap\pa reftab = name of table and columns with world coordinates of the same objects in the reference image in the form: table[,:xlabel,:ylabel]. \\ If the labels are omitted, they are defaulted to :XCEN,:YCEN \ap\pa option = type of transformation to calculate as given below: FREE, all parameters in the transformation are free; EQUAL, the scaling factors in x and y are equal; UNIT, the scaling factors in x and y are equal to 1; SHIFT, the scaling factors in x and y are equal to 1 and rotation angle = 0.0; thus, these options decrease in the degree of freedom for the paramaters of the solution; defaulted to UNIT \ap\pa overlay_flag = OVER,[intensity] - plot positions of the object in table `intab' transformed to the reference frame. \\ Points are plotted in the overlay plane with given intensity, default intensity = 255 (white); defaulted to no overlay \\ The reference frame must be displayed for this option to work! \ap\pa residual_flag = YES or NO - if you want to save the residuals calculated in ALIGN/IMAGE also to be stored in the input table `intab' in columns labeled :XRESIDUAL, :YRESIDUAL and :RESIDUALS; \\ defaulted to NO \ap\sa See also: Chapter 3 of Vol B of the MIDAS User's Guide, \\ CENTER/MOMENT, CENTER/GAUSS, REBIN/ROTATE, ALIGN/CENTER \\ ALIGN/INTER, TUTORIAL/ALIGN \as\no Note: The character column IDENT is used to find matching pairs in the input tables. Thus, this column must exist in both tables! For the SHIFT option one common object is sufficient while the other options require at least 3 common objects in the two tables. The higher the degree of freedom for the paramaters of the solution, the more objects should be used. Also, these objects should not be clustered in one part of the image but, preferably, spread apart covering the whole image area. The resulting rotation angle (in degrees), scaling factor in x and y are stored in the double precision keyword TRANSFRM(1,2,3), the transformation matrix in TRANSFRM(4-7), and the x,y translation in TRANSFRM(8-9). The values in TRANSFRM may be used later on as input for the REBIN/ROTATE command. Preparing the tables, applying ALIGN/IMAGE and finally rebinning the images accordingly is quite a complex process, therefore a command ALIGN/INTER exists to interactively align two images. At most 2000 coord. pairs (objects) are used for the alignment. \on\exs Examples: \ex ALIGN/IMAGE c1 c2 Use columns labeled :XCEN and :YCEN in tables `c1.tbl' and `c2.tbl' to obtain the world coordinates of common objects in the two images, say `im1.bdf' and `im2.bdf', from which tables `c1.tbl' and `c2.tbl' were built. \\ The method is defaulted to UNIT, so the scaling factors in x and y are forced to 1.0. \\ Then use: REBIN/ROTATE im1 im1r KEYWORD im2 \\ to obtain image `im1r.bdf' which is aligned with image `im2.bdf'. \xe\ex ALIGN/IMAGE c1,:X_COORD,:Y_COORD c2,:X_COORD,:Y_COORD F Use columns labeled :X_COORD and :Y_COORD in tables `c1.tbl' and `c2.tbl' to obtain the world coordinates of common objects in the two images from which table `c1.tbl' and `c2.tbl' were built. \\ All transformation coefficients are free. \xe\ex ALIGN/IMAGE c1,:X_COORD,:Y_COORD c2,:X_COORD,:Y_COORD E OV As above but force equal scaling factors in x and y and display calculated positions (using the coefficients just obtained) for the reference points. \xe \sxe