Adjust the HTML that WordPress generates for SVG so they are resized to fit their container

adjust-svg-size.php

<?php

/**
 * Replace WordPress standard SVG width of 1 with 100%
 * @author Alain Schlesser ([email protected])
 * 
 * By default, WordPress renders all SVG files uploaded through the Media
 * Uploader with both width and height at "1".
 *
 * @param  string  $output  HTML output that Genesis has generated for a
 *                          requested image
 * @return string           modified version of the HTML $output
 *
 * @see http://docs.garyjones.co.uk/genesis/2.0.0/function-genesis_get_image.html
 * @see http://www.w3.org/TR/SVG/mimereg.html
 */
function as_avoid_tiny_svgs( $output ) {

	// replace width of "1" with a new width of "100%" and height of "1" with a
	// new height of "auto"
	$output = str_replace(
		'width="1" height="1"',
		'width="100%" height="auto"',
		$output );
	return $output;
}
add_filter( 'genesis_get_image', 'as_avoid_tiny_svgs' );