QubesOS/qubes-linux-utils
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

replace tinting algorithm with one that partially preserves saturation too

Browse Source 
This algorithm partially preserves saturation, for a  better result, but
enforces a minimum chroma, so that greyscale images get tinted.
This commit is contained in:
qubesuser 2017-11-08 17:31:24 +01:00
parent 843ac6c477
commit ee58088dec
1 changed files with 39 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

71
imgconverter/qubesimgconverter/__init__.py
View File

@ -96,31 +96,18 @@ get_from_stream(), get_from_vm(), get_xdg_icon_from_vm(), get_through_dvm()'''
tr, tg, tb = hex_to_int(colour)
tM = max(tr, tg, tb)
tm = min(tr, tg, tb)
tl2 = tM + tm
# (trn/tdn, tgn/tdn, tbn/tdn) is the tint color with lightness set to 0.5
if tl2 == 0 or tl2 == 510: # avoid division by 0
tdn = 2
# (trn/tdn, tgn/tdn, tbn/tdn) is the tint color with maximum saturation
if tm == tM:
trn = 1
tgn = 1
tbn = 1
elif tl2 <= 255:
tdn = tl2
trn = tr
tgn = tg
tbn = tb
tdn = 2
else:
tdn = 510 - tl2
trn = tdn - (255 - tr)
tgn = tdn - (255 - tg)
tbn = tdn - (255 - tb)
# (trni/tdn, tgni/tdn, tbni/tdn) is the inverted tint color with lightness set to 0.5
trni = tdn - trn
tgni = tdn - tgn
tbni = tdn - tbn
tdn255 = tdn * 255
trn = tr - tm
tgn = tg - tm
tbn = tb - tm
tdn = tM - tm
# use a 1D image representation since we only process a single pixel at a time
pixels = self._size[0] * self._size[1]
@ -129,20 +116,40 @@ get_from_stream(), get_from_vm(), get_xdg_icon_from_vm(), get_through_dvm()'''
g = x[:, 1]
b = x[:, 2]
a = x[:, 3]
M = numpy.maximum(numpy.maximum(r, g), b)
m = numpy.minimum(numpy.minimum(r, g), b)
M = numpy.maximum(numpy.maximum(r, g), b).astype('u4')
m = numpy.minimum(numpy.minimum(r, g), b).astype('u4')
# l2 is the lightness of the pixel in the original image in 0-510 range
l2 = M.astype('u4') + m.astype('u4')
l2i = 510 - l2
l2low = l2 <= 255
# Tn/Td is how much chroma range is reserved for the tint color
# 0 -> greyscale image becomes greyscale image
# 1 -> image becomes solid tint color
Tn = 1
Td = 4
# change lightness of tint color to lightness of image pixel
# if l2 is low, just multiply tint color with 0.5 lightness by pixel lightness
# else, invert tint color, multiply by inverted pixel lightness, then invert again
rt = (numpy.select([l2low, True], [l2 * trn, tdn255 - l2i * trni]) // tdn).astype('B')
gt = (numpy.select([l2low, True], [l2 * tgn, tdn255 - l2i * tgni]) // tdn).astype('B')
bt = (numpy.select([l2low, True], [l2 * tbn, tdn255 - l2i * tbni]) // tdn).astype('B')
# set chroma to the original pixel chroma mapped to the Tn/Td .. 1 range
# float c2 = (Tn/Td) + (1.0 - Tn/Td) * c
# set lightness to the original pixel lightness mapped to the range for the new chroma value
# float m2 = m * (1.0 - c2) / (1.0 - c)
c = M - m
c2 = (Tn * 255) + (Td - Tn) * c
c2d = Td
m2 = ((255 * c2d) - c2) * m
# the maximum avoids division by 0 when c = 255 (m2 is 0 anyway, so m2d doesn't matter)
m2d = numpy.maximum((255 - c) * c2d, 1)
# precomputed values
c2d_tdn = tdn * c2d
m2_c2d_tdn = m2 * c2d_tdn
m2d_c2d_tdn = m2d * c2d_tdn
c2_m2d = c2 * m2d
# float vt = m2 + tvn * c2
rt = ((m2_c2d_tdn + trn * c2_m2d) // m2d_c2d_tdn).astype('B')
gt = ((m2_c2d_tdn + tgn * c2_m2d) // m2d_c2d_tdn).astype('B')
bt = ((m2_c2d_tdn + tbn * c2_m2d) // m2d_c2d_tdn).astype('B')
xt = numpy.column_stack((rt, gt, bt, a))
return self.__class__(rgba=xt.tobytes(), size=self._size)