Reverse order of bit in repeating seqence of byte string
imageguy1206 at gmail.com
Sat Jan 3 21:10:15 CET 2009
On Jan 2, 7:33 pm, John Machin <sjmac... at lexicon.net> wrote:
> For some very strange definition of "works". You say you have 'bgr'
> and want to convert it to 'rbg'. The following code converts 'bgr' to
> 'rgb', which is somewhat more plausible, but not what you said you
Well that's embarrassing ... you are correct. I need to convert from
'bgr' to 'rgb'
Thanks to all others for suggestions
FWIW, I realized the the C.types string buffer is/was mutable so
settled on this;
for start in xrange(0, ctypes.sizeof(buffer), 3):
if buffer[start] != buffer[start+2]:
#only need to swap the bits if they are different. ie if
both are white or black, no change is required.
blue, red = buffer[start], buffer[start+2]
buffer[start], buffer[start+2] = red, blue
This was about 30-40% faster that converting to list, processing and
then converting back again.
Will try the array module too
... but I think I need to find a new graphic package rather that makes
working with the bits easier.
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