Get better uploaded quality or save bandwidth: Change the JPEG compression-level of uploaded images and thumbnails.
‘Resized Image Quality’ lets you easily change the compression-level of uploaded JPEG images and thumbnails. Set it for maximum quality when you want images to look their best, or take advantage of lower quality settings to save bandwidth.
The only interface is a slider aqdded to the Settings > Media admin page, making this easier to use than other compression plugins or functions.php settings.