ref: cbf3fb39fd6aafc33505ea514b414021a43baaa8
parent: 3ffb822e925bef3f61dd29796e16e322f00451fc
author: Alexei Podtelezhnikov <[email protected]>
date: Fri Dec 21 09:20:25 EST 2012
* src/tools/cordic.py: Bring up to date with trigonometric core.
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2012-12-21 Alexei Podtelezhnikov <[email protected]>
+
+ * src/tools/cordic.py: Bring up to date with trigonometric core.
+
2012-12-21 Werner Lemberg <[email protected]>
Check parameters of `FT_Outline_New'.
--- a/src/tools/cordic.py
+++ b/src/tools/cordic.py
@@ -2,66 +2,21 @@
import sys, math
#units = 64*65536.0 # don't change !!
-units = 256
+units = 180 * 2**16
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 range(0,32):
-for n in r:
+ x = 0.5**n # tangent value
- if n >= 0:
- x = 1.0/(2.0**n) # tangent value
- else:
- x = 2.0**(-n)
+ angle = math.atan(x) # arctangent
+ angle2 = round(angle*scale) # arctangent in FT_Angle units
- 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
@@ -68,12 +23,11 @@
sys.stdout.write( comma + repr( int(angle2) ) )
comma = ", "
- shrink = shrink * math.cos( angle2/scale)
+ shrink /= math.sqrt( 1 + x*x )
-
print "shrink factor = " + repr( shrink )
-print "shrink factor 2 = " + repr( shrink * (2.0**32) )
-print "expansion factor = " + repr(1/shrink)
+print "shrink factor 2 = " + repr( int( shrink * (2**32) ) )
+print "expansion factor = " + repr( 1/shrink )
print ""