Actually in current version there is not a good way to do this.
However, i've just commited a method github (quality()) that let's you do this for example:
{% set blog_image = page.media.images|first.grayscale().contrast(30).quality(90).brightnes s(-100).colorize(-35,81,122) %}
You can add this method yourself to your current version. It will be part of the next release.