Add text overlays

README.md

@@ -16,7 +16,7 @@ This project is maintained by myself during my spare time. If you like and use i
 ## Usage
 
 ```
-slide [-t rotation_seconds] [-o background_opacity(0..255)] [-b blur_radius] -p image_folder -r
+slide [-t rotation_seconds] [-o background_opacity(0..255)] [-b blur_radius] -p image_folder [-r] [-O overlay_string]
 ```
 
 * `image_folder`: where to search for images (.jpg files)
@@ -26,7 +26,18 @@ slide [-t rotation_seconds] [-o background_opacity(0..255)] [-b blur_radius] -p
 * `rotation_seconds(default=30)`: time until next random image is chosen from the given folder
 * `background_opacity(default=150)`: opacity of the background filling image between 0 (black background) and 255
 * `blur_radius(default=20)`: blur radius of the background filling image
-
+* `-O` is used to create a overlay string.
+  * It defines overlays for all four edges in the order `top-left;top-right;bottom-left;bottom-right`
+  * All edges overlays are separated by `;`
+  * Each edge can either be just a test or contain formatting in the form `margin|fontsize|text`
+  * the text can contain special strings which are replaced during rendering:
+    * `<time>` current time
+    * `<date>` current date
+    * `<datetime>` current time and date
+    * `<filename>` filename of the current image
+    * `<exifdatetime>` time stamp from the EXIF data of the image
+  * Example: `slide -p ./images -O "20|60|Time: <time>;;;Picture taken at <exifdatetime>"`
+      
 ## Dependencies
 
 * libexif