1 files changed, 131 insertions, 0 deletions
diff --git a/pkg/images/imgeom/src/blkav.gx b/pkg/images/imgeom/src/blkav.gx
new file mode 100644
index 00000000..9c83ebab
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+++ b/pkg/images/imgeom/src/blkav.gx
@@ -0,0 +1,131 @@
+# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
+
+include	<imhdr.h>
+include	<error.h>
+
+define	AVG		1	# operation = arithmetic average
+define	SUM		2	# operation = arithmetic sum
+
+# change to (lrdx) in future
+$for (lrd)
+
+# BLKAVG -- Block average or sum on n-dimensional images.
+# For example, block averaging by a factor of 2 means that pixels 1 and 2
+# are averaged to produce the first output pixel, 3 and 4 are averaged to
+# produce the second output pixel, and so on.  Remainder pixels at the end
+# of a line, col, etc. are averaged correctly.
+
+procedure blkav$t (im1, im2, blkfac, option)
+
+pointer	im1			# input image
+pointer im2			# output image
+int	blkfac[IM_MAXDIM]	# blocking factors
+int	option			# block operation (average, sum, ...)
+
+int	num_oblks[IM_MAXDIM], i, count, ndim, dim, nlines_in_sum, nfull_blkx
+int	junk, num_ilines, num_olines, oline
+long	blkin_s[IM_MAXDIM], blkin_e[IM_MAXDIM]
+long	vin_s[IM_MAXDIM], vin_e[IM_MAXDIM], vout[IM_MAXDIM]
+$if (datatype != l)
+PIXEL	sum
+$else
+real	sum
+$endif
+pointer	sp, accum_ptr, iline_ptr, oline_ptr
+
+int	blkcomp(), imggs$t(), impnl$t() 
+errchk	imggs$t(), impnl$t()
+
+begin
+	call smark (sp)
+	call salloc (accum_ptr, IM_LEN(im1, 1), TY_PIXEL)
+
+	# Initialize; input and output vectors, block counters.
+	ndim = IM_NDIM(im1)
+	nfull_blkx = IM_LEN(im1, 1) / blkfac[1]
+	blkin_s[1] = long(1)
+	blkin_e[1] = long(IM_LEN(im1, 1))
+	vin_s[1]   = blkin_s[1]
+	vin_e[1]   = blkin_e[1]
+
+	do i = 1, ndim {
+	    num_oblks[i] = (IM_LEN(im1,i) + blkfac[i] - 1) / blkfac[i]
+	    IM_LEN(im2, i) = num_oblks[i]
+	}
+	num_olines = 1
+	do i = 2, ndim
+	    num_olines = num_olines * num_oblks[i]
+	call amovkl (long(1), vout, IM_MAXDIM)
+
+	# For each sequential output-image line, ...
+	do oline = 1, num_olines {
+
+	    call aclr$t (Mem$t[accum_ptr], IM_LEN(im1, 1))
+	    nlines_in_sum = 0
+
+	    # Compute block vector; initialize dim>1 input vector.
+	    num_ilines = blkcomp (im1, blkfac, vout, blkin_s, blkin_e,
+		vin_s, vin_e)
+
+	    # Output pointer; note impnl$t returns vout for NEXT output line.
+	    junk = impnl$t (im2, oline_ptr, vout)
+
+	    # For all input lines mapping to current output line, ...
+	    do i = 1, num_ilines {
+		# Get line from input image.
+		iline_ptr = imggs$t (im1, vin_s, vin_e, ndim)
+
+		# Increment general section input vector between block bounds.
+		do dim = 2, ndim {
+		    if (vin_s[dim] < blkin_e[dim]) {
+			vin_s[dim] = vin_s[dim] + 1
+			vin_e[dim] = vin_s[dim]
+			break
+		    } else {
+			vin_s[dim] = blkin_s[dim]
+			vin_e[dim] = vin_s[dim]
+		    }
+		}
+
+		# Accumulate line into block sum.  Keep track of no. of 
+		# lines in sum so that we can compute block average later.
+
+		call aadd$t (Mem$t[iline_ptr], Mem$t[accum_ptr],
+		    Mem$t[accum_ptr], IM_LEN(im1,1))
+		nlines_in_sum = nlines_in_sum + 1
+	    }
+
+	    # We now have a templine of sums; average/sum into output buffer
+	    # first the full blocks using a vop.
+	    if (option == AVG)
+		call abav$t (Mem$t[accum_ptr], Mem$t[oline_ptr], nfull_blkx,
+		    blkfac[1])
+	    else
+		call absu$t (Mem$t[accum_ptr], Mem$t[oline_ptr], nfull_blkx,
+		    blkfac[1])
+
+	    # Now average/sum the final partial block in x, if any.
+	    if (nfull_blkx < num_oblks[1]) {
+		sum = 0$f
+		count = 0
+		do i = nfull_blkx * blkfac[1] + 1, IM_LEN(im1,1) {
+		    sum = sum + Mem$t[accum_ptr+i-1]
+		    count = count + 1
+		}
+		if (option == AVG)
+		    Mem$t[oline_ptr+num_oblks[1]-1] = sum / count
+		else
+		    Mem$t[oline_ptr+num_oblks[1]-1] = sum
+	    }
+		
+	    # Block average into output line from the sum of all lines block
+	    # averaged in X.
+	    if (option == AVG)
+		call adivk$t (Mem$t[oline_ptr], PIXEL(nlines_in_sum),
+		    Mem$t[oline_ptr], num_oblks[1])
+	}
+	
+	call sfree (sp)
+end
+
+$endfor