diff -r f9283dc4860d -r 88f2e05288ba misc/libfreetype/src/tools/cordic.py --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/misc/libfreetype/src/tools/cordic.py Mon Apr 25 01:46:54 2011 +0200 @@ -0,0 +1,79 @@ +# compute arctangent table for CORDIC computations in fttrigon.c +import sys, math + +#units = 64*65536.0 # don't change !! +units = 256 +scale = units/math.pi +shrink = 1.0 +comma = "" + +def calc_val( x ): + global units, shrink + angle = math.atan(x) + shrink = shrink * math.cos(angle) + return angle/math.pi * units + +def print_val( n, x ): + global comma + + lo = int(x) + hi = lo + 1 + alo = math.atan(lo) + ahi = math.atan(hi) + ax = math.atan(2.0**n) + + errlo = abs( alo - ax ) + errhi = abs( ahi - ax ) + + if ( errlo < errhi ): + hi = lo + + sys.stdout.write( comma + repr( int(hi) ) ) + comma = ", " + + +print "" +print "table of arctan( 1/2^n ) for PI = " + repr(units/65536.0) + " units" + +# compute range of "i" +r = [-1] +r = r + range(32) + +for n in r: + + if n >= 0: + x = 1.0/(2.0**n) # tangent value + else: + x = 2.0**(-n) + + angle = math.atan(x) # arctangent + angle2 = angle*scale # arctangent in FT_Angle units + + # determine which integer value for angle gives the best tangent + lo = int(angle2) + hi = lo + 1 + tlo = math.tan(lo/scale) + thi = math.tan(hi/scale) + + errlo = abs( tlo - x ) + errhi = abs( thi - x ) + + angle2 = hi + if errlo < errhi: + angle2 = lo + + if angle2 <= 0: + break + + sys.stdout.write( comma + repr( int(angle2) ) ) + comma = ", " + + shrink = shrink * math.cos( angle2/scale) + + +print +print "shrink factor = " + repr( shrink ) +print "shrink factor 2 = " + repr( shrink * (2.0**32) ) +print "expansion factor = " + repr(1/shrink) +print "" +