Author: dmeyer
Date: Sun Feb 19 18:53:57 2006
New Revision: 1202
Modified:
trunk/metadata/src/image/EXIF.py
Log:
ugly hack to make EXIF parsing much faster
Modified: trunk/metadata/src/image/EXIF.py
==============================================================================
--- trunk/metadata/src/image/EXIF.py (original)
+++ trunk/metadata/src/image/EXIF.py Sun Feb 19 18:53:57 2006
@@ -863,15 +863,46 @@
else:
values=[]
signed=(field_type in [6, 8, 9, 10])
- for j in range(count):
- if field_type in (5, 10):
- # a ratio
- value_j=Ratio(self.s2n(offset, 4, signed),
- self.s2n(offset+4, 4, signed))
+ if count > 100 and not field_type in (5, 10):
+ # BEGIN SPEEDUP
+ #
+ # The normal code seeks and reads for each field, see
below.
+ # For a large 'count', this slows down everything. I had
files
+ # with count > 3000 and using this extra code reduces the
+ # complete scanning time from 0.55 to 0.15 seconds.
+ #
+ # This changes are not yet in the original EXIF.py, there
are
+ # only in kaa.metadata for now. If it works like it should,
+ # please send this to the original author. This code still
+ # seeks too much in the file, only reading a very short
number
+ # of bytes.
+ #
+ self.file.seek(self.offset+offset)
+ buffer = self.file.read(typelen * count)
+ if self.endian == 'I':
+ s2n=s2n_intel
else:
- value_j=self.s2n(offset, typelen, signed)
- values.append(value_j)
- offset=offset+typelen
+ s2n=s2n_motorola
+ msb=1L << (8*typelen-1)
+ for j in range(count):
+ value_j = s2n(buffer[count*typelen:(count+1)*typelen])
+ # Sign extension ?
+ if signed:
+ if value_j & msb:
+ value_j=value_j-(msb << 1)
+ values.append(value_j)
+ offset=offset+typelen*count
+ # END SPEEDUP
+ else:
+ for j in range(count):
+ if field_type in (5, 10):
+ # a ratio
+ value_j=Ratio(self.s2n(offset, 4, signed),
+ self.s2n(offset+4, 4, signed))
+ else:
+ value_j=self.s2n(offset, typelen, signed)
+ values.append(value_j)
+ offset=offset+typelen
# now "values" is either a string or an array
if count == 1 and field_type != 2:
printable=str(values[0])
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