output file with specified filesize + original geometry?

[cybersd]

I have pictures between 3 and 30 MB. All this pictures must be convert to the same output filesize 2MB but with the original geometry size.
I try this with -quality, resize etc., but I get different output filesizes or samler geometry.

I need help.....

[fmw42]

What format are your output images? What platform are you using?

Basically, other than your playing with -quality, there is no way to keep the image dimensions the same and get a specific file size as far a I know in IM.

[cybersd]

The Source image file is jpg and the Output file jpg, too.
I use an Linux System (debian, Suse).
I also make Tests with -quality, but the output size e.g. from a 8 MB file is sometimes 2,3 MB and sometimes 5 MB, with the Same quality Percent size.

[fmw42]

As I said you have to use trial an error to get the specified file size by changing -quality as the compression will be image dependent. There is no simple recipe to get a specified file size via -quality in IM.

I am not sure how PS does jpg compression to a given file size for web output.

The only way I know to do it is to iterate on the -quality until you get what you want for the filesize.

[anthony]

ImageMagick JPG coder can do that 'trial and error' for you.

See IM Examples, Common image file Formats, JPEG, Writing options
and specifically the -define jpeg:extent={size} option
http://www.imagemagick.org/Usage/formats/#jpg_write

[fmw42]

I stand corrected. Neat. I learned something new today.

[cybersd]

Thank you! It works fine!