--- rxvt-unicode/src/perl/background	2012/07/14 08:42:54	1.74
+++ rxvt-unicode/src/perl/background	2012/08/14 23:57:07	1.76
@@ -14,6 +14,30 @@
          --background-border
          --background-interval seconds
 
+=head1 QUICK AND DIRTY CHEAT SHEET
+
+Just load a random jpeg image and tile the background with it without
+scaling or anything else:
+
+   load "/path/to/img.jpg"
+
+The same, but use mirroring/reflection instead of tiling:
+
+   mirror load "/path/to/img.jpg"
+
+Load an image and scale it to exactly fill the terminal window:
+
+   scale keep { load "/path/to/img.jpg" }
+
+Implement pseudo-transparency by using a suitably-aligned root pixmap
+as window background:
+
+   rootalign root
+
+Likewise, but keep a blurred copy:
+
+   rootalign keep { blur 10, root }
+
 =head1 DESCRIPTION
 
 This extension manages the terminal background by creating a picture that
@@ -400,6 +424,8 @@
       $base
    }
 
+=back
+
 =head2 TILING MODES
 
 The following operators modify the tiling mode of an image, that is, the
@@ -829,6 +855,8 @@
 Due to idiosyncrasies in the underlying XRender extension, biases less
 than zero can be I<very> slow.
 
+You can also try the experimental(!) C<muladd> operator.
+
 =cut
 
    sub contrast($$;$$;$) {
@@ -855,6 +883,26 @@
       $img
    }
 
+=item muladd $mul, $add, $img # EXPERIMENTAL
+
+First multipliesthe pixels by C<$mul>, then adds C<$add>. This cna be used
+to implement brightness and contrast at the same time, with a wider value
+range than contrast and brightness operators.
+
+Due to numerous bugs in XRender implementations, it can also introduce a
+number of visual artifacts.
+
+Example: increase contrast by a factor of C<$c> without changing image
+brightness too much.
+
+   muladd $c, (1 - $c) * 0.5, $img
+
+=cut
+
+   sub muladd($$$) {
+      $_[2]->muladd ($_[0], $_[1])
+   }
+
 =item blur $radius, $img
 
 =item blur $radius_horz, $radius_vert, $img