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+.help rotate Dec98 images.imgeom
+.ih
+NAME
+rotate -- rotate and shift a list of images
+.ih
+USAGE
+rotate input output rotation
+.ih
+PARAMETERS
+.ls input
+List of images to be rotated.
+.le
+.ls output
+List of output images.
+.le
+.ls rotation
+Angle of rotation of the image in degrees. Positive angles will rotate
+the image counter-clockwise from the x axis.
+.le
+.ls xin = INDEF, yin = INDEF
+The origin of the rotation in pixels. Xin and yin default to the center of
+the input image.
+.le
+.ls xout = INDEF, yout = INDEF
+The origin of the output image. Xout and yout default to the center of the
+output image.
+.le
+.ls ncols = INDEF, nlines = INDEF
+The number of columns and rows in the output image. The default is to
+keep the dimensions the same as the input image. If ncols and nrows is
+less then or equal to zero the program will compute the number of columns
+and rows needed to include the whole image, excluding the effects of
+any origin shifts.
+.le
+.ls interpolant = "linear"
+The interpolant. The options are the following:
+.ls nearest
+Nearest neighbor.
+.le
+.ls linear
+Bilinear interpolation in x and y.
+.le
+.ls poly3
+Third order polynomial in x and y.
+.le
+.ls poly5
+Fifth order polynomial in x and y.
+.le
+.ls spline3
+Bicubic spline.
+.le
+.ls sinc
+2D sinc interpolation. Users can specify the sinc interpolant width by
+appending a width value to the interpolant string, e.g. sinc51 specifies
+a 51 by 51 pixel wide sinc interpolant. The sinc width will be rounded up to
+the nearest odd number.  The default sinc width is 31 by 31.
+.le
+.ls lsinc
+Look-up table sinc interpolation. Users can specify the look-up table sinc
+interpolant width by appending a width value to the interpolant string, e.g.
+lsinc51 specifies a 51 by 51 pixel wide look-up table sinc interpolant. The user
+supplied sinc width will be rounded up to the nearest odd number. The default
+sinc width is 31 by 31 pixels. Users can specify the resolution of the lookup
+table sinc by appending the look-up table size in square brackets to the
+interpolant string, e.g. lsinc51[20] specifies a 20 by 20 element sinc
+look-up table interpolant with a pixel resolution of 0.05 pixels in x and y.
+The default look-up table size and resolution are 20 by 20 and 0.05 pixels
+in x and y respectively.
+.le
+.ls drizzle
+2D drizzle resampling. Users can specify the drizzle pixel fraction in x and y
+by appending a value between 0.0 and 1.0 in square brackets to the
+interpolant string, e.g. drizzle[0.5]. The default value is 1.0.
+The value 0.0 is increased internally to 0.001. Drizzle resampling
+with a pixel fraction of 1.0 in x and y is equivalent to fractional pixel
+rotated block summing (fluxconserve = yes) or averaging (flux_conserve = no)  if
+xmag and ymag are > 1.0.
+.le
+.le
+.ls boundary = "nearest"
+The choices are:
+.ls nearest
+Use the value of the nearest boundary pixel.
+.le
+.ls constant
+Use a constant value.
+.le
+.ls reflect
+Generate a value by reflecting around the boundary.
+.le
+.ls wrap
+Generate a value by wrapping around to the opposite side of the image.
+.le
+.le
+.ls constant = 0.
+The value of the constant for constant boundary extension.
+.le
+.ls nxblock = 512, nyblock = 512
+If the dimensions of the output image are less than nxblock and nyblock
+then the entire image is rotated at once. Otherwise nxblock by nyblock
+segments of the image are rotated.
+.le
+.ih
+DESCRIPTION
+
+ROTATE rotates the list of images in input by rotation degrees and writes
+the output to the images specified by output. The origins of the input and
+output images may be specified by setting xin, yin, xout and yout. The
+transformation is described below.
+
+.nf
+    xt = (x - xin) * cos (rotation) - (y - yin) * sin (rotation) + xout
+    yt = (x - xin) * sin (rotation) + (y - yin) * cos (rotation) + yout
+
+.fi
+
+The output image gray levels are determined by interpolating in the input
+image at the positions of the transformed output pixels. ROTATE uses the
+routines in the 2-D interpolation package.
+
+.ih
+EXAMPLES
+
+.nf
+1. Rotate an image 45 degrees around its center.
+
+   cl> rotate m51 m51r45 45.0
+
+2. Rotate an image by 45 degrees around (100., 100.) and
+   shift the origin to (150., 150.0) using bicubic interpolation.
+
+   cl> rotate m92 m92r45 45.0 xin=100. yin=100. xout=150. yout=150.\
+   >>> interp=poly3
+
+3. Rotate an image 90 degrees counter-clockwise and clockwise around its
+   center. Note the use of imtranspose and image section notation.
+
+   cl> imtranspose m92[*,-*] m92d90
+
+   cl> imtranspose m92[-*,*] m92d270
+
+4. Rotate an image 180 degrees counter-clockwise. Note the use of imcopy
+   and image section notation.
+
+   cl> imcopy m92[-*,-*] m92d180
+.fi
+
+.ih
+TIMINGS
+It requires approximately 70 and 290 cpu seconds to rotate a 512 by 512
+real image using bilinear and biquintic interpolation respectively
+(Vax 11/750 fpa).
+.ih
+BUGS
+The interpolation operation is done in real arithmetic. However the output
+type of the pixels is set equal to the input type. This can lead to truncation
+problems for integer images.
+
+Simple 90, 180, 270 etc degree rotations are best performed using the
+imtranspose task and/or image section notation.
+.ih
+SEE ALSO
+imtranspose, imshift, magnify, lintran, geotran, geomap
+.endhelp