feat(decor:shadow): add a background cli flag -b or --bg

 - this flag accepts `white`, `black` and `transparent`
 - it defaults to `white`
 - so that the target color where the gif needs to be embedded can be changed
 - extend the CHANGELOG.md

Author: sassman

CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [0.3.0] - XXXX
 ### Added
 - command line parameter `-d` or `--decor` that allows to turn on and off effects [feat(decor:shadow)]
+- command line parameter `-b` or `--bg` that allows to change the target background color to white, black or transparent
 - command line parameter `-v` or `--verbose` that shows insights on the window name and window id for the curious
 - turn on the new shadow decor effect by default 
 ![demo](./docs/demo-shadow.gif)

src/cli.rs

@@ -24,6 +24,16 @@ pub fn launch<'a>() -> ArgMatches<'a> {
                 .long("decor")
                 .help("Decorates the animation with certain, mostly border effects")
         )
+        .arg(
+            Arg::with_name("bg")
+                .takes_value(true)
+                .possible_values(&["white", "black", "transparent"])
+                .default_value("white")
+                .required(false)
+                .short("b")
+                .long("bg")
+                .help("Background color when decors are used")
+        )
         .arg(
             Arg::with_name("natural-mode")
                 .value_name("natural")

src/decor_effect.rs

@@ -15,7 +15,7 @@ use tempfile::TempDir;
 ///     -layers merge \
 ///     t-rec-frame-000000251.tga
 /// ```
-pub fn apply_shadow_effect(time_codes: &[u128], tempdir: &TempDir) -> Result<()> {
+pub fn apply_shadow_effect(time_codes: &[u128], tempdir: &TempDir, bg_color: String) -> Result<()> {
     apply_effect(
         time_codes,
         tempdir,
@@ -25,7 +25,7 @@ pub fn apply_shadow_effect(time_codes: &[u128], tempdir: &TempDir) -> Result<()>
                 .arg("(")
                 .args(&["+clone", "-background", "black", "-shadow", "100x20+0+0"])
                 .arg(")")
-                .args(&["+swap", "-background", "white"])
+                .args(&["+swap", "-background", bg_color.as_str()])
                 .args(&["-layers", "merge"])
                 .arg(file.to_str().unwrap())
                 .spawn()

src/main.rs

@@ -119,6 +119,7 @@ fn main() -> Result<()> {
         apply_shadow_effect(
             &time_codes.lock().unwrap(),
             tempdir.lock().unwrap().borrow(),
+            args.value_of("bg").unwrap().to_string(),
         )?
     }