gistfile1.php

<?php
add_filter( 'jpeg_quality', 'tgm_image_full_quality' );
add_filter( 'wp_editor_set_quality', 'tgm_image_full_quality' );
/**
 * Filters the image quality for thumbnails to be at the highest ratio possible.
 *
 * Supports the new 'wp_editor_set_quality' filter added in WP 3.5.
 *
 * @since 1.0.0
 *
 * @param int $quality  The default quality (90).
 * @return int $quality Amended quality (100).
 */
function tgm_image_full_quality( $quality ) {

    return 100;

}