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pdfminer.six
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PNG predictor added

pull/1/head
Yusuke Shinyama 2011-06-07 00:46:33 +09:00
parent 18a5058af6
commit 0278076ea8
1 changed files with 13 additions and 6 deletions
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19
pdfminer/utils.py
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@ -25,15 +25,22 @@ def apply_png_predictor(pred, colors, columns, bitspercomponent, data):
# PNG none
buf += line1
elif pred == '\x01':
# PNG sub
b = 0
for c in line1:
b += ord(c)
buf += chr(b & 255)
# PNG sub (UNTESTED)
c = 0
for b in line1:
c = (c+ord(b)) & 255
buf += chr(c)
elif pred == '\x02':
# PNG up
for (a,b) in zip(line0,line1):
buf += chr((ord(a)+ord(b)) & 255)
c = (ord(a)+ord(b)) & 255
buf += chr(c)
elif pred == '\x03':
# PNG average (UNTESTED)
c = 0
for (a,b) in zip(line0,line1):
c = ((c+ord(a)+ord(b))/2) & 255
buf += chr(c)
else:
# unsupported
raise ValueError(pred)