Update desc

Author: yuanchuan

README.md

@@ -41,7 +41,9 @@ Generate an image from the css-doodle source file. The source file can be a `.cs
 * `-x, --scale`: Scale factor of the generated image, defaults to 1.
 * `-s, --selector`: CSS selector to target the rendered node, defaults to `css-doodle`.
 * `-d, --delay`: Delay after the image is rendered, e.g, `2s`.
-* `-t, --time`: Record screen for a specific time, e.g, `10s.
+* `-t, --time`: Record screen for a specific time, e.g, `10s`.
+* `-ws, --window-size`: `The size of the rendered window, e.g, `800x600`, defaults to `1600x900`.
+* `--mp4`: Transform the generated `webm` file into `mp4`.
 
 ```bash
 cssd render
@@ -57,6 +59,13 @@ Screen recording:
 cssd render -t 10s
 ```
 
+By default the generated video is in `webm` format, you can transform it automatically into `mp4` by adding `--mp4` option, or use an output filename with `.mp4` extension.
+
+```bash
+cssd render -t 10s --mp4
+cssd render -o result.mp4
+```
+
 ### preview
 Open a window to preview the css-doodle source file. The source file can be either `.css` or `.cssd`.
 

bin/index.js

@@ -46,9 +46,9 @@ program
     .option('-x, --scale <scale>', 'Scale factor of the generated image, defaults to `2`')
     .option('-s, --selector <selector>', 'CSS selector to target the rendered node, defaults to `css-doodle`')
     .option('-d, --delay <delay>', 'Delay after the image is rendered, e.g, `2s`')
-    .option('-t, --time <time>', 'Record screen for a specific time, e.g, `10s')
+    .option('-t, --time <time>', 'Record screen for a specific time, e.g, `10s`')
     .option('-ws, --window-size <size>', 'The size of the rendered window, e.g, `800x600`, defaults to `1600x900`')
-    .option('--mp4', 'Generate an mp4 video')
+    .option('--mp4', 'Transform the generated `webm` file into `mp4`')
     .action(handleRender);
 
 program