Deletes an image style.
$style: An image style array.
$replacement_style_name: (optional) When deleting a style, specify a replacement style name so that existing settings (if any) may be converted to a new style.
TRUE on success.
function image_style_delete($style, $replacement_style_name = '') {
image_style_flush($style);
db_delete('image_effects')
->condition('isid', $style['isid'])
->execute();
db_delete('image_styles')
->condition('isid', $style['isid'])
->execute();
// Let other modules update as necessary on save.
$style['old_name'] = $style['name'];
$style['name'] = $replacement_style_name;
module_invoke_all('image_style_delete', $style);
return TRUE;
}