Legacy ImageMagick Discussions Archive

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.....

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.

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.

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.

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

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

Thank you! It works fine!