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To compare images from different instruments it is desirable for them to have the same scale and orientation. IRAF provides a number of tools which allow manipulation of images. For qp files QPOE Utilities.
To magnify or shrink (both linear transformations), specify the reduction factor in both x and y.
im> imlintran.ncols = 0 # necessary to set values in empty im> imlintran.nlines = 0 # pixels to zero. Use for shrinking. im> imlintran casa casa_m 0. 0. 2. 2. # input image casa.imh is shrunk factor of 2 # and result put in casa_m.imh
or this can be accomplished with,
im> magnify casa casa_m 0.5 0.5.
To shift, specify the old and new position of the image center.
im> imlintran casa_m casa_mt 0. 0. 1. 1. xin=256 yin=256 xout = 276 yout=456 # moves the image casa_m 20 pixels to the right and 200 pixels up.
To embed a small image in a larger (blank) array
im> magnify casa casa_big 1 1 x1=-56 x2=200 y1=-56 y2=200 # This example places the 144x144 array, ``casa'' at the center of a 256x256 array # with no change of scale.
To rotate, specify angle of rotation in degrees (positive is counter clockwise).
im> imlintran casa_m casa_mr 30. 30. 1. 1. # rotates image casa_m.imh # 30 deg ccw im> imlintran casa_m casa _mf 0. 180 1. 1. # flips the image, # output is mirror image # There is 180 rotation of y axis
A flip about the y axis, however, is more easily accomplished by
im> imcopy casa_m[*,-*] casa_mf
Note that several operations can be done at the same time
im> imlintran casa casa_mrt 45. 45. 1.25 1.25 xin=512 yin=512 xout=492 yout=519