A scaling function for CONTENTdm

calculate_contentdm_scaling.php

<?php

/**
 * Return CONTENTdm scaling of $width and $height to $maxwidth and $maxheight.
 *
 * @param string $width starting width
 * @param string $height starting height
 * @param string $maxwidth width limit
 * @param string $maxheight height limit
 * @return array dmscale, dmwidth, dmheight
 * @author Stephen Ball
 */
function calculate_contentdm_scaling($width, $height, $maxwidth, $maxheight)
{
    $original_width = $width;
    $original_height = $height;
    // scale the width and height if necessary to get under maxwidth
    if ($width > $maxwidth) {
        $width_diff = $width / $maxwidth;
        $width = $width / $width_diff;
        $height = $height / $width_diff;
        $target_dimension = $maxwidth;
        $original_dimension = $original_width;
    }
    // scale the height and width if necessary to get under maxheight
    if ($height > $maxheight) {
        $height_diff = $height / $maxheight;
        $height = $height / $height_diff;
        $width = $width / $height_diff;
        $target_dimension = $maxheight;
        $original_dimension = $original_height;
    }
    // construct the scaling in "dm" values
    $dmHeight = round($height, 0);
    $dmWidth = round($width, 0);
    $dmScale = ($target_dimension * 100) / $original_dimension;
    return array($dmScale, $dmWidth, $dmHeight);
}

?>