Performance Drop from 6.8.7-9

[sireeshala]

Exactly performance drop was found After 6.8.7-8 Means the drop starts from 6.8.7-9
We have gone through the logs and found out that the performance problem may caused by the following modification with rev. 13858+13859 in MagickCore/attribute.c

The modification causes these overhead steps if a b/w image is coded as G.4 TIFF:
• The image is converted from b/w to grayscale
• The grayscale image is normalized (enhances the contrast of a color image by mapping the darkest 2% of all pixel to black and the brightest 1% to white according to comment)
• The grayscale image is converted back to b/w

We observed the drop for b/w(black and white) and grayscale
attribute.patch gives the required modifications to avoid the over heads caused.

https://www.dropbox.com/s/isb3uhh9glbdgz1/attribute.c?dl=0
https://www.dropbox.com/s/2twn1xjxv8l5fep/attribute.patch?dl=0

[magick]

We can reproduce the problem you posted and applied your patch in ImageMagick 6.9.1-2 Beta, available by sometime tomorrow. Thanks.