From ae19a1314a224e88e8696d0579d05df8c8068e4a Mon Sep 17 00:00:00 2001
From: Justin Brooks <justin@jzbrooks.com>
Date: Sun, 12 Jan 2025 20:12:42 -0500
Subject: [PATCH] Add a background color CLI option

---
 CHANGELOG.md                             | 11 +++--------
 README.md                                |  9 ++++++---
 src/main/kotlin/com/jzbrooks/vat/Main.kt | 22 +++++++++++++++++-----
 3 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4050de7..9e9478a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,16 +4,11 @@
 
 ### Added
 - Build targets for windows and linux systems
+- Handle SVGs supported by vgo
+- `--background-color` option (hexadecimal RGBA format)
 
 ### Changed
-
-### Deprecated
-
-### Removed
-
-### Fixed
-
-### Security
+- Default to transparent background
 
 ## 0.0.2
 
diff --git a/README.md b/README.md
index 9c0819c..8e33fd1 100644
--- a/README.md
+++ b/README.md
@@ -25,10 +25,13 @@ The image can be found at http://plurib.us/1shot/2008/eleven_below/.
 ```
 > vat [options] [file]
 
+vat renders vector artwork (SVG & Android Vector Drawable) to the terminal.
+
 Options:
-  -s --scale      scale factor (float or integer)
-  -h --help       print this message
-  -v --version    print the version number
+  --background-color   background color in hexadecimal RGBA format
+  -s --scale           scale factor (float or integer)
+  -h --help            print this message
+  -v --version         print the version number
 ```
 
 > `java -jar vat` for Windows
diff --git a/src/main/kotlin/com/jzbrooks/vat/Main.kt b/src/main/kotlin/com/jzbrooks/vat/Main.kt
index 2006f73..bebebe0 100644
--- a/src/main/kotlin/com/jzbrooks/vat/Main.kt
+++ b/src/main/kotlin/com/jzbrooks/vat/Main.kt
@@ -19,9 +19,10 @@ private const val HELP_MESSAGE = """
 vat renders vector artwork (SVG & Android Vector Drawable) to the terminal.
 
 Options:
-  -s --scale      scale factor (float or integer)
-  -h --help       print this message
-  -v --version    print the version number
+  --background-color   background color in hexadecimal RGBA format
+  -s --scale           scale factor (float or integer)
+  -h --help            print this message
+  -v --version         print the version number
 """
 
 @OptIn(ExperimentalEncodingApi::class)
@@ -41,7 +42,7 @@ fun main(args: Array<String>) {
         return
     }
 
-    val scale = argReader.readOption("s|scale")?.let {
+    val scale = argReader.readOption("scale|s")?.let {
         val factor = it.toFloatOrNull()
         if (factor != null) {
             factor
@@ -51,6 +52,17 @@ fun main(args: Array<String>) {
         }
     } ?: 1f
 
+    val backgroundColor = argReader.readOption("background-color")?.let {
+        val rgba = it.removePrefix("0x").chunked(2).mapNotNull { it.toIntOrNull(16) }
+        if (rgba.size == 4) {
+            // The RGBA color must be re-packed as ARGB for skia, per its color packing rules
+            (rgba[3] shl 24) or (rgba[0] shl 16) or (rgba[1] shl 8) or rgba[2]
+        } else {
+            System.err.println("Unable to parse $it as a hexadecimal RGBA color e.g. 0xFF0000FF (red)")
+            null
+        }
+    } ?: 0
+
     val path = argReader.readArguments().first()
     val image =
         File(path).inputStream().use { inputStream ->
@@ -88,7 +100,7 @@ fun main(args: Array<String>) {
     }
 
     val surface = Surface.makeRasterN32Premul((width * scale).roundToInt(), (height * scale).roundToInt())
-    surface.canvas.clear(0)
+    surface.canvas.clear(backgroundColor)
 
     val visitor = DrawingVisitor(surface.canvas, scale, scale)
     image.accept(visitor)