+ * You can control how the image is compressed by passing _comp_, which
+ * is a hash whose :lossy entry is true if the image should be
+ * compressed lossily. If :lossy is true, the :quality entry
+ * (0-100, default 100) sets the compression quality.
+ * If :lossy is false, the :level entry (0-9, default 9) sets the
+ * compression level. If _comp_ isn't passed, then the
+ * image is stored losslessly.