Here's a great little line of code to put into your wp theme's functions php file: add_filter('jpeg_quality', function($arg){return 100;});
This will make the jpg compression quality full so degradation will be minimal.
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Change the Default WordPress Thumbnail JPG Compression Quality – Inspect Element
Quick question for WordPressers: Does the WP featured image functionality degrade the image at all?— Orman Clark (@ormanclark) March 21, 2012 A