[magick-developers] jpg to jpg bigger than through TIFF first

[dan1]

Hello.

I have seen a quite strange behaviour lately:
If I convert a picture from jpeg to jpeg in a smaller size, then I end up with 323Kbytes. However, if I do first convert this same source file to a TIFF (no resize), and then resize it from tiff to jpeg in the same dimension than the other file, I end up with only 255Kbytes.

So there seems to be a problem in how the conversion is handled inside the algorithm.
Visually speaking, I think that both results quality are exactly the same (watching closely), but the only difference is that we lose a lot of disk space from jpg to jpg..

Can someone tell me if this is a bug, a lack of optimization (I think so), or if there is something else to do ?
I would personnally suggest to re-code this part to make that the file would be uncompressed in memory the same way than in TIFF, and then compressed again, as the resulting compression is much better !

Currently I think of doing a script which does the conversion in two phases, but doing it directly so inside the algorithm would be great !

Here is the jpg source file I used, in 1600x1200 pixels:
http://www.edenpics.com/pub/bugs/001-001.jpg

This is the resulting file when converted directly from jpg to a resized jpg using the comand: 'convert -geometry 1024x768 -quality 82 -strip 001-001.jpg 001-001b.jpg:
http://www.edenpics.com/pub/bugs/001-001b.jpg

Here is the converted file when first converting from jpeg to TIFF with 'convert 001-001.jpg 001-001tiff.tif'
http://www.edenpics.com/pub/bugs/001-001tiff.tif

Here is the converted file from this last TIFF to jpeg resized using the command: 'convert -geometry 1024x768 -quality 82 -strip 001-001tiff.tif 001-001d.jpg'
http://www.edenpics.com/pub/bugs/001-001d.jpg

I am using ImageMagick V6.0.7.1-14 running on CentOS 4.3.

Please make some tries and tell me what you think.

Thank you,
Daniel