I use always:
- quality in 85
- progressive (comprobed compression)
- a very tiny gausssian blur to optimize the size (0.05 or 0.5 of radius) depends on the quality and size of the picture, this notably optimizes the size of the jpeg.
- Strip any comment or exif tag
in imagemagick should be
convert -strip -interlace Plane -gaussian-blur 0.05 -quality 85% source.jpg result.jpg
hope this be useful.
http://stackoverflow.com/questions/7261855/recommendation-for-compressing-jpg-files-with-imagemagick
