diff options
| -rw-r--r-- | Doc/whatsnew/3.4.rst | 7 | ||||
| -rw-r--r-- | Lib/colorsys.py | 18 | ||||
| -rw-r--r-- | Lib/test/test_colorsys.py | 32 | ||||
| -rw-r--r-- | Misc/NEWS | 3 |
4 files changed, 51 insertions, 9 deletions
diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst index 44762a1..80b4b01 100644 --- a/Doc/whatsnew/3.4.rst +++ b/Doc/whatsnew/3.4.rst @@ -251,6 +251,13 @@ platform-dependent. (Contributed by Christian Heimes in :issue:`11016`.) The module supports new file types: door, event port and whiteout. +colorsys +-------- + +The number of digits in the coefficients for the RGB --- YIQ conversions have +been expanded so that they match the FCC NTSC versions. The change in +results should be less than 1% and may better match results found elsewhere. + Optimizations ============= diff --git a/Lib/colorsys.py b/Lib/colorsys.py index a6c0cf6..b93e384 100644 --- a/Lib/colorsys.py +++ b/Lib/colorsys.py @@ -33,17 +33,25 @@ TWO_THIRD = 2.0/3.0 # YIQ: used by composite video signals (linear combinations of RGB) # Y: perceived grey level (0.0 == black, 1.0 == white) # I, Q: color components +# +# There are a great many versions of the constants used in these formulae. +# The ones in this library uses constants from the FCC version of NTSC. def rgb_to_yiq(r, g, b): y = 0.30*r + 0.59*g + 0.11*b - i = 0.60*r - 0.28*g - 0.32*b - q = 0.21*r - 0.52*g + 0.31*b + i = 0.74*(r-y) - 0.27*(b-y) + q = 0.48*(r-y) + 0.41*(b-y) return (y, i, q) def yiq_to_rgb(y, i, q): - r = y + 0.948262*i + 0.624013*q - g = y - 0.276066*i - 0.639810*q - b = y - 1.105450*i + 1.729860*q + # r = y + (0.27*q + 0.41*i) / (0.74*0.41 + 0.27*0.48) + # b = y + (0.74*q - 0.48*i) / (0.74*0.41 + 0.27*0.48) + # g = y - (0.30*(r-y) + 0.11*(b-y)) / 0.59 + + r = y + 0.9468822170900693*i + 0.6235565819861433*q + g = y - 0.27478764629897834*i - 0.6356910791873801*q + b = y - 1.1085450346420322*i + 1.7090069284064666*q + if r < 0.0: r = 0.0 if g < 0.0: diff --git a/Lib/test/test_colorsys.py b/Lib/test/test_colorsys.py index e405b8a..a24e3ad 100644 --- a/Lib/test/test_colorsys.py +++ b/Lib/test/test_colorsys.py @@ -1,4 +1,4 @@ -import unittest, test.support +import unittest import colorsys def frange(start, stop, step): @@ -69,8 +69,32 @@ class ColorsysTest(unittest.TestCase): self.assertTripleEqual(hls, colorsys.rgb_to_hls(*rgb)) self.assertTripleEqual(rgb, colorsys.hls_to_rgb(*hls)) -def test_main(): - test.support.run_unittest(ColorsysTest) + def test_yiq_roundtrip(self): + for r in frange(0.0, 1.0, 0.2): + for g in frange(0.0, 1.0, 0.2): + for b in frange(0.0, 1.0, 0.2): + rgb = (r, g, b) + self.assertTripleEqual( + rgb, + colorsys.yiq_to_rgb(*colorsys.rgb_to_yiq(*rgb)) + ) + + def test_yiq_values(self): + values = [ + # rgb, yiq + ((0.0, 0.0, 0.0), (0.0, 0.0, 0.0)), # black + ((0.0, 0.0, 1.0), (0.11, -0.3217, 0.3121)), # blue + ((0.0, 1.0, 0.0), (0.59, -0.2773, -0.5251)), # green + ((0.0, 1.0, 1.0), (0.7, -0.599, -0.213)), # cyan + ((1.0, 0.0, 0.0), (0.3, 0.599, 0.213)), # red + ((1.0, 0.0, 1.0), (0.41, 0.2773, 0.5251)), # purple + ((1.0, 1.0, 0.0), (0.89, 0.3217, -0.3121)), # yellow + ((1.0, 1.0, 1.0), (1.0, 0.0, 0.0)), # white + ((0.5, 0.5, 0.5), (0.5, 0.0, 0.0)), # grey + ] + for (rgb, yiq) in values: + self.assertTripleEqual(yiq, colorsys.rgb_to_yiq(*rgb)) + self.assertTripleEqual(rgb, colorsys.yiq_to_rgb(*yiq)) if __name__ == "__main__": - test_main() + unittest.main() @@ -202,6 +202,9 @@ Core and Builtins Library ------- +- Issue #14323: Expanded the number of digits in the coefficients for the + RGB -- YIQ conversions so that they match the FCC NTSC versions. + - Issue #17998: Fix an internal error in regular expression engine. - Issue #17557: Fix os.getgroups() to work with the modified behavior of |