[SOLVED] IM6 and IM7 give very different -resize results

[NicolasRobidoux]

Bleeding edge, up to date, IM6 and IM7: svn rev 9368, both compiled in HDRI mode on up to date Linux Mint 12.

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convert rose: input_rose.jpg
convert input_rose.jpg -resize 500% IM6rose.jpg
magick input_rose.jpg -resize 500% IM7rose.jpg

The max difference between the two images is 39, which is huge.
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I'll try to narrow down the problem.

[NicolasRobidoux]

I think IM7 is the broken one.

[NicolasRobidoux]

It's not a JPEG issue: Same if I use png.

[NicolasRobidoux]

It's not a negative lobe issue: Same with -filter Triangle.

[NicolasRobidoux]

Just to make sure it's clear:

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convert -version
Version: ImageMagick 6.7.9-6 2012-09-15 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenMP  HDRI
magick -version
Version: ImageMagick 7.0.0-0 2012-09-15 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenMP  HDRI

[NicolasRobidoux]

Not so sure it's IM7 that's broken.

[NicolasRobidoux]

The bleeding edge IM6 compiled with everything default (make clean && ./configure && make && sudo make install) gives the exact same result as shown in http://www.imagemagick.org/Usage/resize ... _sigmoidal (IM v6.7.9-1) with the following command:

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convert rose: -colorspace RGB  -filter Lanczos  -resize 200x \
           -colorspace sRGB rose_resize_RGB.new.png

(And an extremely different result when compiled in HDRI, which is not surprising given the negative lobes.)
I don't know what is going on.

[NicolasRobidoux]

I should go back to earlier IM7 and see if there is a difference, but I'll go buy winter tires instead.

[NicolasRobidoux]

-distort resize appears to be fine.
It's a -resize issue.

[NicolasRobidoux]

As of svn rev 9379, this seems to be fixed.

[NicolasRobidoux]

Still broken:

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convert rose: input_rose.jpg
convert input_rose.jpg -resize 500% IM6rose.jpg
magick input_rose.jpg -resize 500% IM7rose.jpg

still gives different images.
What fooled me for a minute is that

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magick rose: -resize 500% IM7rose.jpg
convert rose: -resize 500% IM6rose.jpg

give identical images.

[NicolasRobidoux]

A-ah! Could it be that IM6 and IM7 use different JPEG settings?

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convert rose: input_rose.png
convert input_rose.png -resize 500% IM6rose.png
magick input_rose.png -resize 500% IM7rose.png

do give identical images.

[NicolasRobidoux]

No: convert rose: roseIM6.jpg (with IM6 convert) and magick rose: roseIM7.jpg give identical images.

[NicolasRobidoux]

jpeg.c was just updated in both IM6 and IM7, but

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convert rose: input_rose.jpg
convert input_rose.jpg -resize 500% IM6rose.jpg
magick input_rose.jpg -resize 500% IM7rose.jpg

still gives different images.
For reference:

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magick -version
Version: ImageMagick 7.0.0-0 2012-09-17 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenMP  HDRI  
convert -version
Version: ImageMagick 6.7.9-7 2012-09-16 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2012 ImageMagick Studio LLC
Features: OpenMP  HDRI

[NicolasRobidoux]

Again for the record, this is how I compile both IM6 and IM7 (--enable-hdri is now unnecessary with IM7, but it should not hurt):

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make clean && CFLAGS="-march=native" CXXFLAGS="-march=native" ./configure --enable-hdri && make && sudo make install