Stop Image Compression in Theme

My theme is automatically compressing my images and it is making them look pixelated because I optimize my images prior to upload. The only thing I can find in my research is that I need to add this: add_filter( 'jpeg_quality', create_function( '', 'return 100;' ) ); to my functions.php… I have tried that and had no luck. I use the theme Minimalix and am very, very new to wordpress so any help would be MUCH appreciated… This is driving me insane!