diff --git a/.gitignore b/.gitignore
index 74a7157..35022e0 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,3 @@
 /target
 /font
-/res
+font.sff
diff --git a/Cargo.lock b/Cargo.lock
index 1cf0e7e..aa4b812 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -386,6 +386,12 @@ dependencies = [
  "either",
 ]
 
+[[package]]
+name = "itoa"
+version = "1.0.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
+
 [[package]]
 name = "jobserver"
 version = "0.1.33"
@@ -407,6 +413,8 @@ name = "karlos-helper"
 version = "0.1.0"
 dependencies = [
  "image",
+ "serde",
+ "serde_json",
 ]
 
 [[package]]
@@ -760,6 +768,12 @@ version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8a0d197bd2c9dc6e53b84da9556a69ba4cdfab8619eb41a8bd1cc2027a0f6b1d"
 
+[[package]]
+name = "ryu"
+version = "1.0.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "28d3b2b1366ec20994f1fd18c3c594f05c5dd4bc44d8bb0c1c632c8d6829481f"
+
 [[package]]
 name = "serde"
 version = "1.0.219"
@@ -780,6 +794,18 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "serde_json"
+version = "1.0.141"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30b9eff21ebe718216c6ec64e1d9ac57087aad11efc64e32002bce4a0d4c03d3"
+dependencies = [
+ "itoa",
+ "memchr",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "serde_spanned"
 version = "0.6.9"
diff --git a/Cargo.toml b/Cargo.toml
index e8cd968..099585d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,3 +5,5 @@ edition = "2021"
 
 [dependencies]
 image = "0.25.6"
+serde = { version="1.0.219", features=["derive"] }
+serde_json = "1.0.141"
diff --git a/example/ascii.png b/example/ascii.png
new file mode 100644
index 0000000..fb24902
Binary files /dev/null and b/example/ascii.png differ
diff --git a/example/german.png b/example/german.png
new file mode 100644
index 0000000..a9ffda9
Binary files /dev/null and b/example/german.png differ
diff --git a/example/index.json b/example/index.json
new file mode 100644
index 0000000..d7ea5fb
--- /dev/null
+++ b/example/index.json
@@ -0,0 +1,26 @@
+{
+  "char_width": 8,
+  "char_height": 18,
+  "splitters": [
+    {
+      "Table": {
+        "path": "example/ascii.png",
+        "nrows": 6,
+        "ncols": 16,
+        "start_number": 32
+      }
+    },
+    {
+      "Individual": {
+        "path": "example/german.png",
+        "numbers": [228, 196, 246, 214, 252, 220, 223]
+      }
+    },
+    {
+      "Single": {
+        "path": "example/replacement.png",
+        "number": 65533
+      }
+    }
+  ]
+}
diff --git a/example/replacement.png b/example/replacement.png
new file mode 100644
index 0000000..3abb3e2
Binary files /dev/null and b/example/replacement.png differ
diff --git a/src/main.rs b/src/main.rs
index 0862bbc..db4aa1c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -41,7 +41,7 @@ fn load_font_dir<P: AsRef<Path>>(dir_with_images: P) -> HashMap<u32, BWImage> {
 fn image_split_table<P, Q>(
     src_image: P,
     dst_dir: Q,
-    start_number: usize,
+    start_number: u32,
     nrows: usize,
     ncols: usize,
     width_per_elem: usize,
@@ -76,7 +76,7 @@ fn image_split_table<P, Q>(
 fn image_split_individual<P, Q>(
     src_image: P,
     dst_dir: Q,
-    numbers: &[usize],
+    numbers: &[u32],
     width_per_elem: usize,
     height_per_elem: usize,
 ) where
@@ -126,15 +126,75 @@ fn sorted_numbers_into_ranges(sorted_numbers: &[u32]) -> Vec<TableRange> {
     out
 }
 
+#[derive(Debug, serde::Deserialize)]
+enum Splitter {
+    Table {
+        path: String,
+        nrows: usize,
+        ncols: usize,
+        start_number: u32,
+    },
+    Individual {
+        path: String,
+        numbers: Vec<u32>,
+    },
+    Single {
+        path: String,
+        number: u32,
+    },
+}
+
+#[derive(Debug, serde::Deserialize)]
+struct Index {
+    char_width: usize,
+    char_height: usize,
+    splitters: Vec<Splitter>,
+}
+
 fn main() {
-    image_split_table("res/ascii.png", "font", 32, 6, 16, 8, 18);
-    image_split_individual(
-        "res/german.png",
-        "font",
-        &[0x00e4, 0x00c4, 0x00f6, 0x00d6, 0x00fc, 0x00dc, 0x00df][..],
-        8,
-        18,
-    );
+    std::fs::remove_dir_all("font").unwrap();
+    std::fs::create_dir("font").unwrap();
+    let args: Vec<String> = std::env::args().collect();
+    let index: Index = serde_json::from_str(&std::fs::read_to_string(&args[1]).unwrap()).unwrap();
+    for splitter in index.splitters {
+        match splitter {
+            Splitter::Table {
+                path,
+                nrows,
+                ncols,
+                start_number,
+            } => {
+                image_split_table(
+                    path,
+                    "font",
+                    start_number,
+                    nrows,
+                    ncols,
+                    index.char_width,
+                    index.char_height,
+                );
+            }
+            Splitter::Individual { path, numbers } => {
+                image_split_individual(
+                    path,
+                    "font",
+                    &numbers[..],
+                    index.char_width,
+                    index.char_height,
+                );
+            }
+            Splitter::Single { path, number } => {
+                image_split_individual(
+                    path,
+                    "font",
+                    &[number][..],
+                    index.char_width,
+                    index.char_height,
+                );
+            }
+        }
+    }
+
     let map = load_font_dir("font");
     let mut sorted_keys: Vec<u32> = map.keys().copied().collect();
     sorted_keys.sort();