Interpolation and file size

Discussions on NConvert - the command line tool for image conversion and manipulation

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Guidance
Posts: 9
Joined: Sun Oct 26, 2003 12:32 am

Interpolation and file size

Post by Guidance »

I'm looking for a converter to make thumbnails for my web page. I tried both xn and abc (advanced batch converter) and found xnconvert generate much more larger jpg files. For example, a 760kB 1600x1200 jpg => 120 width thumbnail jpg, will result 140~200kB in xn with 10~30 quality level, but only 3kB in abc with default quality level and bspline interpolation. And furthermore, the converted picture looks much nicer than xn!!
I use below command for xn:

nconvert -quiet -q 30 -opthuff -ratio -rflag decr -rtype linear -o d:\tmp\test1.jpg -truecolors -resize 120 -out jpeg "d:\tmp\big.jpg"

and this for abc:

abc.exe "d:\tmp\big.jpg" /reduce=(120,0,4) /convert=d:\tmp\test2.jpg

Why there's a so big gap? Does interpolation influence file size so much?
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xnview
Author of XnView
Posts: 43988
Joined: Mon Oct 13, 2003 7:31 am
Location: France

Re: interpolation and file size

Post by xnview »

Guidance wrote:I'm looking for a converter to make thumbnails for my web page. I tried both xn and abc (advanced batch converter) and found xnconvert generate much more larger jpg files. For example, a 760kB 1600x1200 jpg => 120 width thumbnail jpg, will result 140~200kB in xn with 10~30 quality level, but only 3kB in abc with default quality level and bspline interpolation. And furthermore, the converted picture looks much nicer than xn!!
I use below command for xn:

nconvert -quiet -q 30 -opthuff -ratio -rflag decr -rtype linear -o d:\tmp\test1.jpg -truecolors -resize 120 -out jpeg "d:\tmp\big.jpg"

and this for abc:

abc.exe "d:\tmp\big.jpg" /reduce=(120,0,4) /convert=d:\tmp\test2.jpg

Why there's a so big gap? Does interpolation influence file size so much?
By default, nconvert keep EXIF/IPTC data. To remove them, you must use -rmeta
Regards. Pierre.
Guidance
Posts: 9
Joined: Sun Oct 26, 2003 12:32 am

Thanks!

Post by Guidance »

It works, thanks! Now only 2~3kB with -q 60 typically. And the biggest problem of ABC is, that's not free, I can only use it for one month :(