I have rewritten the function like this. Still the same problem. Seems that WP itself removes inline style tags…
protected function render_style_block() {
// Calculate the width (in %) of each image
$used_margin = $this->display_options [‘columns’] * 2;
$width = floor ( (100 – $used_margin) / $this->display_options [‘columns’] );
$output = ‘<style type=\”text/css\”>#{‘;
$output .= $this->album_id;
$output .= ‘}.epa-image{width:{‘;
$output .= $width;
$output .= ‘%;}</style>’;
return $ouput;
}