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improve upon premultiplied alpha tests in a51678d307

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This commit is contained in:
Dane Springmeyer 2012-08-28 18:53:27 -07:00
parent 9a51b31e01
commit 6aa9043352
1 changed files with 97 additions and 33 deletions
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130
tests/python_tests/compositing_test.py
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@ -11,49 +11,77 @@ def setup():
# from another directory we need to chdir()
os.chdir(execution_path('.'))
def validate_pixels_are_demultiplied(image):
bad_pixels = []
def is_pre(color,alpha):
return (color*255.0/alpha) <= 255
def debug_image(image,step=2):
for x in range(0,image.width(),step):
for y in range(0,image.height(),step):
pixel = image.get_pixel(x,y)
alpha = (pixel >> 24) & 0xff
red = pixel & 0xff
green = (pixel >> 8) & 0xff
blue = (pixel >> 16) & 0xff
print "rgba(%s,%s,%s,%s) at %s,%s" % (red,green,blue,alpha,x,y)
# note: it is impossible to know for all pixel colors
# we can only detect likely cases of non premultiplied colors
def validate_pixels_are_not_premultiplied(image):
over_alpha = False
transparent = True
fully_opaque = True
for x in range(0,image.width(),2):
for y in range(0,image.height(),2):
pixel = image.get_pixel(x,y)
r = pixel & 0xff
g = (pixel >> 8) & 0xff
b = (pixel >> 16) & 0xff
a = (pixel >> 24) & 0xff
is_valid = (r >=0 and r < 256) and \
(g >=0 and g < 256) and \
(b >=0 and b < 256) and \
(a >=0 and a < 256)
if not is_valid:
bad_pixels.append("rgba(%s,%s,%s,%s) at %s,%s" % (r,g,b,a,x,y))
num_bad = len(bad_pixels)
return (num_bad == 0,num_bad)
alpha = (pixel >> 24) & 0xff
if alpha > 0:
transparent = False
if alpha < 255:
fully_opaque = False
red = pixel & 0xff
green = (pixel >> 8) & 0xff
blue = (pixel >> 16) & 0xff
color_max = max(red,green,blue)
if color_max > alpha:
over_alpha = True
return over_alpha or transparent or fully_opaque
def validate_pixels_are_not_premultiplied2(image):
looks_not_multiplied = False
for x in range(0,image.width(),2):
for y in range(0,image.height(),2):
pixel = image.get_pixel(x,y)
alpha = (pixel >> 24) & 0xff
#each value of the color channels will never be bigger than that of the alpha channel.
if alpha > 0:
red = pixel & 0xff
green = (pixel >> 8) & 0xff
blue = (pixel >> 16) & 0xff
if red > 0 and red > alpha:
print 'red: %s, a: %s' % (red,alpha)
looks_not_multiplied = True
return looks_not_multiplied
def validate_pixels_are_premultiplied(image):
bad_pixels = []
for x in range(0,image.width(),2):
for y in range(0,image.height(),2):
pixel = image.get_pixel(x,y)
red = pixel & 0xff
green = (pixel >> 8) & 0xff
blue = (pixel >> 16) & 0xff
alpha = (pixel >> 24) & 0xff
a2 = alpha
if a2 == 0:
a2 = 1
else:
a2 = a2*256
is_valid = (red >=0 and red/a2 < 256) and \
(green >=0 and red/a2 < 256) and \
(blue >=0 and red/a2 < 256) and \
(alpha >=0 and alpha < 256)
if not is_valid:
import pdb;pdb.set_trace()
bad_pixels.append("rgba(%s,%s,%s,%s) at %s,%s" % (red,green,blue,alpha,x,y))
if alpha > 0:
pixel = image.get_pixel(x,y)
red = pixel & 0xff
green = (pixel >> 8) & 0xff
blue = (pixel >> 16) & 0xff
is_valid = ((0 <= red <= alpha) and is_pre(red,alpha)) \
and ((0 <= green <= alpha) and is_pre(green,alpha)) \
and ((0 <= blue <= alpha) and is_pre(blue,alpha)) \
and (alpha >= 0 and alpha <= 255)
if not is_valid:
bad_pixels.append("rgba(%s,%s,%s,%s) at %s,%s" % (red,green,blue,alpha,x,y))
num_bad = len(bad_pixels)
return (num_bad == 0,bad_pixels)
def test_compare_images():
b = mapnik.Image.open('./images/support/b.png')
b.premultiply()
@ -67,9 +95,8 @@ def test_compare_images():
if not valid[0]:
print '%s not validly pre-:\n\t%s pixels (%s)' % (name,len(valid[1]),valid[1][0])
a.demultiply()
valid = validate_pixels_are_demultiplied(a)
if not valid[0]:
print '%s not validly de-:\n\t%s pixels (%s)' % (name,len(valid[1]),valid[1][0])
if not validate_pixels_are_not_premultiplied(a):
print '%s not validly demultiplied' % (name)
a.save(actual)
expected_im = mapnik.Image.open(expected)
# compare them
@ -81,6 +108,43 @@ def test_compare_images():
#b.save('/tmp/mapnik-comp-op-test-original-mask.png')
#eq_(b.tostring(),expected_b.tostring(), '/tmp/mapnik-comp-op-test-original-mask.png is no longer equivalent to original mask: ./images/support/b.png')
def test_pre_multiply_status():
b = mapnik.Image.open('./images/support/b.png')
# not premultiplied yet, should appear that way
result = validate_pixels_are_not_premultiplied(b)
eq_(result,True)
# not yet premultiplied therefore should return false
result = validate_pixels_are_premultiplied(b)
eq_(result[0],False)
# now actually premultiply the pixels
b.premultiply()
# now checking if premultiplied should succeed
result = validate_pixels_are_premultiplied(b)
eq_(result[0],True)
# should now not appear to look not premultiplied
result = validate_pixels_are_not_premultiplied(b)
eq_(result,False)
# now actually demultiply the pixels
b.demultiply()
# should now appear demultiplied
result = validate_pixels_are_not_premultiplied(b)
eq_(result,True)
def test_pre_multiply_status_of_map1():
m = mapnik.Map(256,256)
im = mapnik.Image(m.width,m.height)
eq_(validate_pixels_are_not_premultiplied(im),True)
mapnik.render(m,im)
eq_(validate_pixels_are_not_premultiplied(im),True)
def test_pre_multiply_status_of_map2():
m = mapnik.Map(256,256)
m.background = mapnik.Color(1,1,1,255)
im = mapnik.Image(m.width,m.height)
eq_(validate_pixels_are_not_premultiplied(im),True)
mapnik.render(m,im)
eq_(validate_pixels_are_not_premultiplied(im),True)
if __name__ == "__main__":
setup()