doc image saving and Tek mode menu functions

docs/mintty.1

@@ -874,7 +874,12 @@ PNG, JPEG, GIF, TIFF, BMP, Exif.
 Mintty supports Tektronix 4014 mode. It switches to Tek emulation on the 
 xterm sequence DECSET 38 (`\e[?38h`). It is suggested to adjust the window 
 size to the Tektronix 4010 resolution and aspect ratio before 
-(`echo -en "\e[4;$780;$1024t"`).
+(`echo -en "\e[4;$780;$1024t"`). The \fBtek\fP utility available in 
+the mintty utils repository \fIhttps://github.com/mintty/utils\fP helps to 
+enter Tek mode and set up some environment information properly.
+
+While in Tek mode, the context menu provides the Tektronix mode functions 
+RESET (like xterm), PAGE (minor reset), and COPY ("hard" copy to image file).
 
 .SS Emoji display support
 
@@ -899,6 +904,14 @@ configured as a relative path name using POSIX syntax (forward slashes).
 
 If Shift is held, the function also opens the HTML page.
 
+.SS Image dump of terminal contents
+
+Mintty can save the visual contents of the terminal screen in an image file 
+\fBmintty.date_time.png\fP. This is supported from the context menu or via 
+user-definable key functions. The current terminal dimensions are used for 
+the image size except in Tek mode, where one of the original Tek sizes is 
+used (depending on whether 12-bit pixel addresses are in effect).
+
 .SS Diagnostic support
 
 .TP

wiki/Changelog.md

@@ -4,10 +4,13 @@ Vector graphics
 Window handling
   * Prevent mouse wheel double interpretation, also fixing speed issues (mintty/wsltty#238).
   * Handle proper link attributes when screen is scrolled (#1021).
+  * Image saving feature for terminal contents (png format), DEC and Tek.
 
 Configuration
   * Support resource configuration directories via links (#1016).
   * New option PrintableControls to make controls visible (#1019).
+  * New options Tek*.
+  * New user-definable functions save-image, tek-copy, tek-page, tek-reset.
 
 ### 3.2.0 (20 June 2020) ###