Adds different thumbnail sizes and setups up default jpeg quality to be 100%

WordPressThemeSetup.php

<?php
function application_setup() {

	// Thumbnail sizes. Change as needed.
	// NOTE: These only take affect on new uploaded images.
	add_image_size('icon', 50, 50, true);
	add_image_size('small', 150, 150, true); // small, 150px width, 150px height, crop: true
	add_image_size('medium', 250, 250, true);
	add_image_size('large', 500, 500, true);
	add_image_size('xlarge', 1000, 1000, true);
	add_image_size('banner', 1400, 200, true);

	// Do NOT compress jpegs. We want beautiful images.
	add_filter('jpeg_quality', create_function( '', 'return 100;' ) );

}

// Sets up your theme-based functions
add_action('after_setup_theme', 'application_setup');
?>