JPEG Quality Settings allwows you to fine tune the quality settings Wordpress uses for making JPEG thumnails.

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By default WordPress forces all thumbnails be set to a quality level of 82. But what if you want to change that? Sure the 
jpeg qualtiy filters exist if you want to code in a value, but they affect all JPEG thumbnails which may not be desirable.
For example you might want a blog background to be of a lower quality, hence lowering the filesize and increasing the speed 
of which the page loads.
By using the JPEG Quality Settings plugin you can now customize the quality based on whatever values you want.

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