diff options
author | Qt by Nokia <qt-info@nokia.com> | 2011-04-27 12:05:43 +0200 |
---|---|---|
committer | axis <qt-info@nokia.com> | 2011-04-27 12:05:43 +0200 |
commit | 38be0d13830efd2d98281c645c3a60afe05ffece (patch) | |
tree | 6ea73f3ec77f7d153333779883e8120f82820abe /src/3rdparty/freetype/src/tools/cordic.py |
Initial import from the monolithic Qt.
This is the beginning of revision history for this module. If you
want to look at revision history older than this, please refer to the
Qt Git wiki for how to use Git history grafting. At the time of
writing, this wiki is located here:
http://qt.gitorious.org/qt/pages/GitIntroductionWithQt
If you have already performed the grafting and you don't see any
history beyond this commit, try running "git log" with the "--follow"
argument.
Branched from the monolithic repo, Qt master branch, at commit
896db169ea224deb96c59ce8af800d019de63f12
Diffstat (limited to 'src/3rdparty/freetype/src/tools/cordic.py')
-rw-r--r-- | src/3rdparty/freetype/src/tools/cordic.py | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/src/3rdparty/freetype/src/tools/cordic.py b/src/3rdparty/freetype/src/tools/cordic.py new file mode 100644 index 0000000000..3f80c5f09a --- /dev/null +++ b/src/3rdparty/freetype/src/tools/cordic.py @@ -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 "" + |