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# APMAPR -- Vector linear transformation. Map the range of pixel values
# a1, a2 from a into the range b1, b2 into b. It is assumed that a1 < a2
# and b1 < b2.
real procedure apmapr (a, a1, a2, b1, b2)
real a # the value to be mapped
real a1, a2 # the numbers specifying the input data range
real b1, b2 # the numbers specifying the output data range
real minout, maxout, aoff, boff
real scalar
begin
scalar = (real (b2) - real (b1)) / (real (a2) - real (a1))
minout = min (b1, b2)
maxout = max (b1, b2)
aoff = a1
boff = b1
return (max(minout, min(maxout, real((a - aoff) * scalar) + boff)))
end
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