Updated usage documentation

README.md

@@ -1,5 +1,12 @@
 # Cast2Gif
-An pure Python ANSI terminal emulator that can render AsciiCast terminal recordings to an animated GIF. 
+A pure Python ANSI terminal emulator that can render AsciiCast terminal recordings to an animated GIF or screenshot.
+
+Cast2Gif can also generate its own recordings directly, without requiring asciinema to be installed (see the `--exec` option).
+
+For example, to generate a PNG screenshot of the output of the `ls` command, run
+```bash
+cast2gif --screenshot --output ls.png  --exec  "ls"
+```
 
 ## Quickstart
 
@@ -13,26 +20,40 @@ This will automatically install the `cast2gif` executable in your path.
 ## Usage
 
 ```
-usage: cast2gif [-h] [-v] [-o OUTPUT] [--force] [--font FONT] [-s FONT_SIZE]
+usage: cast2gif [-h] [-v] [--exec ...] [--hide-prompt] [--ps1 PS1] [-o OUTPUT]
+                [--force] [--screenshot] [--font FONT] [-s FONT_SIZE]
                 [--fps FPS] [--idle-time-limit IDLE_TIME_LIMIT] [--loop LOOP]
-                [--quiet] [--width WIDTH] [--height HEIGHT]
-                ASCIICAST
+                [--quiet] [--width WIDTH] [--height HEIGHT] [--auto-size]
+                [ASCIICAST]
 
 Converts AsciiCast terminal recordings to animated GIFs
 
 positional arguments:
   ASCIICAST             The AsciiCast v2 file to convert, or '-' for STDIN
+                        (the default)
 
-optional arguments:
+options:
   -h, --help            show this help message and exit
   -v, --version         Print version information and exit
+  --exec ..., -c ...    Instead of parsing an AsciiCast v2 file, run the
+                        command immediately after `--exec` and use its output
+  --hide-prompt         By default, when using the `--exec` argument to run a
+                        command, the command prompt is included before the
+                        command output; this argument hides the prompt and
+                        only includes the output
+  --ps1 PS1             The PS1 command prompt to use in conjuction with the
+                        `--exec` output (default="${PS1}", if it is set,
+                        otherwise "$ " in green)
   -o OUTPUT, --output OUTPUT
                         The path for the output GIF file, or '-' for STDOUT
                         (default is the input filename plus '.gif', or STDOUT
                         if the input file is STDIN)
   --force               Overwrite the output file even if it already exists
+  --screenshot, -sc     Render a screenshot rather than an animated gif
   --font FONT           Path to a TrueType font for rendering; defaults to
-                        SourceCodePro
+                        SourceCodePro; this argument can be supplied multiple
+                        times, with additional fonts used in the event that
+                        one is missing a required glyph
   -s FONT_SIZE, --font-size FONT_SIZE
                         Font size (default=12)
   --fps FPS             Speficy the number of frames per second in the output
@@ -48,6 +69,9 @@ optional arguments:
   --quiet               Suppress all logging and status printouts
   --width WIDTH         Override the output width
   --height HEIGHT       Override the output height
+  --auto-size           Override the output dimensions to be wide enough to
+                        fit every line; if specified, this overrides the
+                        `--width` option
 ```
 
 ## License