def _is_device_cs(xref, doc: fitz.Document):
'''Check whether object xref is a device based color space.
'''
# cs definition
obj_contents = doc.xrefObject(xref)
# for now, just check /ICCBased CS:
# it's treated as a device based cs if /Device[Gray|RGB|CMYK] exists in /Alternate.
#
# [ /ICCBased 15 0 R ]
#
# <<
# /Alternate /DeviceRGB
# /Filter /FlateDecode
# /Length 2597
# /N 3
# >>
if '/ICCBased' in obj_contents:
name, x, *_ = obj_contents[1:-1].strip().split()
ICC_contents = doc.xrefObject(int(x))
return '/Alternate /Device' in ICC_contents
# ignore all other color spaces, may include if facing associated cases
return False
def _check_device_cs(doc:fitz.Document, page:fitz.Page):
'''Get all color space name used in current page and check if they're device based color space.'''
# default device based cs
cs = {
'/DeviceGray': True,
'/DeviceRGB' : True,
'/DeviceCMYK': True
}
# content of page object, e.g.
# <<
# ...
# /Resources <<
# ...
# /ColorSpace <<
# /Cs6 14 0 R
# >>
# >>
# /Rotate 0
# /Type /Page
# >>
obj_contents = doc.xrefObject(page.xref)
cs_found = False
for line_ in obj_contents.splitlines():
line = line_.strip()
# check start/end of color space block
if not cs_found and line.startswith('/ColorSpace'):
cs_found = True
continue
if not cs_found:
continue
elif line=='>>':
break
# now within cs block, e.g. /Cs6 14 0 R
cs_name, xref, *_ = line.split()
cs[cs_name] = _is_device_cs(int(xref), doc)
return cs