Con PHP algo asi
Código PHP:
<?php
$file = "algo.jpg"
header("Content-Disposition: attachment; filename='$file'\n");
header("Content-transfer-encoding: binary\n");
header("Content-length: " . filesize($file) . "\n");
if (strstr($HTTP_USER_AGENT,"MSIE") && strstr($HTTP_USER_AGENT,"Mac_PowerPC")){
header("Content-type: application/force-download\n");
}else{
header("Content-type: application/octet-stream\n");
}
$fp=fopen($file, "r");
fpassthru($fp);
?>