Page speed – Page speed at which images are not compressed

Original picture Bart-had-a-groove.gif Size is 753.43 KB,

Processed image bart-had-a-groove.gif.pagespeed.ce.gB3ARqAHA8.gif Size is still 753.43 KB,

Mods used:

        pagespeed DisableRewriteOnNoTransform off;

pagespeed EnableFilters rewrite_images;
pagespeed EnableFilters sprite_images;
pagespeed EnableFilters insert_image_dimensions;
pagespeed EnableFilters resize_images;
pagespeed EnableFilters resize_rendered_image_dimensions;
pagespeed EnableFilters rewrite_images;
pagespeed EnableFilters strip_image_color_profile;
pagespeed EnableFilters strip_image_meta_data;

The file is renamed and headers contain the page speed so page speed works.

Could it be that the original image was already compressed to the maximum or something?