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# AMAPS -- Linear transformation, type short. The range of pixel values
# A1 to A2 are mapped into the range B1 to B2 using a linear transformation.
# Values less than A1 or greater than A2 are mapped into the values B1 and
# B2 upon output.
.data 0
.set A, 4
.set B, 8
.set NPIX, 12
.set A1, 16
.set A2, 20
.set B1, 24
.set B2, 28
.align 2
.globl _amaps_
.text
# AMAPS (a, b, npix, a1, a2, b1, b2)
#
# scalar = real (b2 - b1) / real (a2 - a1)
# minout = min (b1, b2)
# maxout = max (b1, b2)
#
# do i = 1, npix
# b[i] = max(minout, min(maxout,
# PIXEL((a[i] - a1) * scalar) + b1))
#
# Registers:
# r0 last_a
# r1 a
# r2 b
# r3 scalar
# r4 minout
# r5 maxout
# r6 a1
# r7 b1
_amaps_:
.word 01774 # save r2-r9
movl A(ap), r1
movl B(ap), r2
mull3 $2, *NPIX(ap), r0
addl2 r1, r0
movw *A1(ap), r6
movw *B1(ap), r7
movw *A2(ap), r8
movw *B2(ap), r9
subw3 r7, r9, r3 # r3 = (b2 - b1) / (a2 - a1)
cvtwf r3, r3
subw3 r6, r8, r4
cvtwf r4, r4
divf2 r4, r3
cmpw r7, r9 # b1 <= b2
bleq L1
movw r9, r4 # no, min=b2, max=b1
movw r7, r5
jbr L2
L1: movw r7, r4 # yes, min=b1, max=b2
movw r9, r5
L2:
subw3 r6, (r1)+, r8 # r8 = a[i] - a1
cvtwf r8, r8
mulf2 r3, r8 # (..) * scalar
cvtfw r8, r8
addw2 r7, r8 # (..) + b1
cmpw r8, r4 # r8 < minout?
bgtr L3
movw r4, (r2)+
jbr L5
L3:
cmpw r8, r5 # r8 > maxout?
blss L4
movw r5, (r2)+
jbr L5
L4:
movw r8, (r2)+ # new value in range
L5:
cmpl r1, r0
blssu L2 # loop again
ret
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