diff --git a/Cargo.lock b/Cargo.lock
index aa4b812..b8cc995 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -17,6 +17,56 @@ dependencies = [
  "equator",
 ]
 
+[[package]]
+name = "anstream"
+version = "0.6.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "301af1932e46185686725e0fad2f8f2aa7da69dd70bf6ecc44d6b703844a3933"
+dependencies = [
+ "anstyle",
+ "anstyle-parse",
+ "anstyle-query",
+ "anstyle-wincon",
+ "colorchoice",
+ "is_terminal_polyfill",
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle"
+version = "1.0.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "862ed96ca487e809f1c8e5a8447f6ee2cf102f846893800b20cebdf541fc6bbd"
+
+[[package]]
+name = "anstyle-parse"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e7644824f0aa2c7b9384579234ef10eb7efb6a0deb83f9630a49594dd9c15c2"
+dependencies = [
+ "utf8parse",
+]
+
+[[package]]
+name = "anstyle-query"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c8bdeb6047d8983be085bab0ba1472e6dc604e7041dbf6fcd5e71523014fae9"
+dependencies = [
+ "windows-sys",
+]
+
+[[package]]
+name = "anstyle-wincon"
+version = "3.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "403f75924867bb1033c59fbf0797484329750cfbe3c4325cd33127941fabc882"
+dependencies = [
+ "anstyle",
+ "once_cell_polyfill",
+ "windows-sys",
+]
+
 [[package]]
 name = "anyhow"
 version = "1.0.98"
@@ -150,12 +200,58 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9555578bc9e57714c812a1f84e4fc5b4d21fcb063490c624de019f7464c91268"
 
+[[package]]
+name = "clap"
+version = "4.5.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed87a9d530bb41a67537289bafcac159cb3ee28460e0a4571123d2a778a6a882"
+dependencies = [
+ "clap_builder",
+ "clap_derive",
+]
+
+[[package]]
+name = "clap_builder"
+version = "4.5.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "64f4f3f3c77c94aff3c7e9aac9a2ca1974a5adf392a8bb751e827d6d127ab966"
+dependencies = [
+ "anstream",
+ "anstyle",
+ "clap_lex",
+ "strsim",
+]
+
+[[package]]
+name = "clap_derive"
+version = "4.5.41"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef4f52386a59ca4c860f7393bcf8abd8dfd91ecccc0f774635ff68e92eeef491"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "clap_lex"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b94f61472cee1439c0b966b47e3aca9ae07e45d070759512cd390ea2bebc6675"
+
 [[package]]
 name = "color_quant"
 version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
 
+[[package]]
+name = "colorchoice"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b05b61dc5112cbb17e4b6cd61790d9845d13888356391624cbe7e41efeac1e75"
+
 [[package]]
 name = "crc32fast"
 version = "1.5.0"
@@ -377,6 +473,12 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "is_terminal_polyfill"
+version = "1.70.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7943c866cc5cd64cbc25b2e01621d07fa8eb2a1a23160ee81ce38704e97b8ecf"
+
 [[package]]
 name = "itertools"
 version = "0.12.1"
@@ -412,6 +514,7 @@ checksum = "00810f1d8b74be64b13dbf3db89ac67740615d6c891f0e7b6179326533011a07"
 name = "karlos-helper"
 version = "0.1.0"
 dependencies = [
+ "clap",
  "image",
  "serde",
  "serde_json",
@@ -564,6 +667,12 @@ version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
+[[package]]
+name = "once_cell_polyfill"
+version = "1.70.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4895175b425cb1f87721b59f0f286c2092bd4af812243672510e1ac53e2e0ad"
+
 [[package]]
 name = "paste"
 version = "1.0.15"
@@ -842,6 +951,12 @@ version = "1.15.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "67b1b7a3b5fe4f1376887184045fcf45c69e92af734b7aaddc05fb777b6fbd03"
 
+[[package]]
+name = "strsim"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
+
 [[package]]
 name = "syn"
 version = "2.0.104"
@@ -943,6 +1058,12 @@ version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5a5f39404a5da50712a4c1eecf25e90dd62b613502b7e925fd4e4d19b5c96512"
 
+[[package]]
+name = "utf8parse"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
+
 [[package]]
 name = "v_frame"
 version = "0.3.9"
@@ -1039,6 +1160,79 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a751b3277700db47d3e574514de2eced5e54dc8a5436a3bf7a0b248b2cee16f3"
 
+[[package]]
+name = "windows-sys"
+version = "0.59.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e38bc4d79ed67fd075bcc251a1c39b32a1776bbe92e5bef1f0bf1f8c531853b"
+dependencies = [
+ "windows-targets",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9b724f72796e036ab90c1021d4780d4d3d648aca59e491e6b98e725b84e99973"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_gnullvm",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32a4622180e7a0ec044bb555404c800bc9fd9ec262ec147edd5989ccd0c02cd3"
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09ec2a7bb152e2252b53fa7803150007879548bc709c039df7627cabbd05d469"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e9b5ad5ab802e97eb8e295ac6720e509ee4c243f69d781394014ebfe8bbfa0b"
+
+[[package]]
+name = "windows_i686_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0eee52d38c090b3caa76c563b86c3a4bd71ef1a819287c19d586d7334ae8ed66"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "240948bc05c5e7c6dabba28bf89d89ffce3e303022809e73deaefe4f6ec56c66"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "147a5c80aabfbf0c7d901cb5895d1de30ef2907eb21fbbab29ca94c5b08b1a78"
+
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "24d5b23dc417412679681396f2b49f3de8c1473deb516bd34410872eff51ed0d"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.52.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
+
 [[package]]
 name = "winnow"
 version = "0.7.12"
diff --git a/Cargo.toml b/Cargo.toml
index 099585d..dc66f0b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,6 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+clap = { version = "4.5.42", features = ["derive"] }
 image = "0.25.6"
 serde = { version="1.0.219", features=["derive"] }
 serde_json = "1.0.141"
diff --git a/src/main.rs b/src/main.rs
index db4aa1c..07eb17a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,6 +2,7 @@ use std::collections::HashMap;
 use std::path::Path;
 
 mod image_wrapper;
+use clap::Parser;
 use image_wrapper::BWImage;
 mod sff;
 
@@ -35,6 +36,7 @@ fn load_font_dir<P: AsRef<Path>>(dir_with_images: P) -> HashMap<u32, BWImage> {
         assert!(!map.contains_key(&number));
         map.insert(number, img);
     }
+    assert!(!map.is_empty());
     map
 }
 
@@ -151,59 +153,31 @@ struct Index {
     splitters: Vec<Splitter>,
 }
 
-fn main() {
-    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,
-                );
-            }
-        }
+fn do_inspect<P: AsRef<Path>>(path: P) {
+    let read_file = std::fs::read(path).unwrap();
+    let fd = sff::decode(&read_file);
+    for i in 32..128 {
+        fd.print_symbol(fd.find_codepoint(i).unwrap());
     }
+}
 
-    let map = load_font_dir("font");
+fn do_create<P: AsRef<Path>, Q: AsRef<Path>>(font_dir: P, dest: Q, encoding: sff::Encoding) {
+    let map = load_font_dir(font_dir);
+    let (char_width, char_height) = {
+        let random_element = map.values().next().unwrap();
+        (
+            random_element.width as usize,
+            random_element.height as usize,
+        )
+    };
     let mut sorted_keys: Vec<u32> = map.keys().copied().collect();
     sorted_keys.sort();
     let ranges = sorted_numbers_into_ranges(&sorted_keys);
 
     let fdo = sff::FileDescOut {
-        char_width: 8,
-        char_height: 18,
-        encoding: sff::Encoding::BitPerPix4,
+        char_width,
+        char_height,
+        encoding,
         tables: ranges
             .into_iter()
             .map(|rng| sff::TableOut {
@@ -217,7 +191,121 @@ fn main() {
             .collect(),
     };
 
-    std::fs::write("font.sff", fdo.encode()).unwrap();
+    std::fs::write(dest, fdo.encode()).unwrap();
+}
+
+fn do_split<P: AsRef<Path>, Q: AsRef<Path>>(index: P, font_dir: Q) {
+    if std::fs::exists(font_dir.as_ref()).unwrap() {
+        std::fs::remove_dir_all(font_dir.as_ref()).unwrap();
+    }
+    std::fs::create_dir(font_dir.as_ref()).unwrap();
+    let index: Index = serde_json::from_str(&std::fs::read_to_string(index).unwrap()).unwrap();
+    println!("{:#?}", index);
+    for splitter in index.splitters {
+        match splitter {
+            Splitter::Table {
+                path,
+                nrows,
+                ncols,
+                start_number,
+            } => {
+                image_split_table(
+                    path,
+                    font_dir.as_ref(),
+                    start_number,
+                    nrows,
+                    ncols,
+                    index.char_width,
+                    index.char_height,
+                );
+            }
+            Splitter::Individual { path, numbers } => {
+                image_split_individual(
+                    path,
+                    font_dir.as_ref(),
+                    &numbers[..],
+                    index.char_width,
+                    index.char_height,
+                );
+            }
+            Splitter::Single { path, number } => {
+                image_split_individual(
+                    path,
+                    font_dir.as_ref(),
+                    &[number][..],
+                    index.char_width,
+                    index.char_height,
+                );
+            }
+        }
+    }
+}
+
+#[derive(clap::Parser, Debug)]
+struct Cli {
+    #[command(subcommand)]
+    cmd: Command,
+}
+
+#[derive(clap::Subcommand, Debug)]
+enum Command {
+    Inspect {
+        path: String,
+    },
+    Create {
+        #[arg(long)]
+        font_dir: String,
+        #[arg(short, long)]
+        encoding: String,
+        dest: String,
+    },
+    Split {
+        #[arg(long)]
+        index: String,
+        #[arg(long)]
+        font_dir: String,
+    },
+    SplitAndCreate {
+        #[arg(long)]
+        index: String,
+        #[arg(long)]
+        font_dir: String,
+        #[arg(short, long)]
+        encoding: String,
+        dest: String,
+    },
+}
+
+fn str_to_encoding(s: &str) -> sff::Encoding {
+    match s {
+        "BitPerPix1" => sff::Encoding::BitPerPix1,
+        "BitPerPix2" => sff::Encoding::BitPerPix2,
+        "BitPerPix4" => sff::Encoding::BitPerPix4,
+        "BitPerPix8" => sff::Encoding::BitPerPix8,
+        _ => panic!("unknown encoding"),
+    }
+}
+
+fn main() {
+    let cli = Cli::parse();
+    match cli.cmd {
+        Command::Inspect { path } => do_inspect(path),
+        Command::Create {
+            font_dir,
+            encoding,
+            dest,
+        } => do_create(font_dir, dest, str_to_encoding(&encoding)),
+        Command::Split { index, font_dir } => do_split(index, font_dir),
+        Command::SplitAndCreate {
+            index,
+            font_dir,
+            encoding,
+            dest,
+        } => {
+            do_split(index, &font_dir);
+            do_create(&font_dir, dest, str_to_encoding(&encoding));
+        }
+    }
 }
 
 #[cfg(test)]
diff --git a/src/sff.rs b/src/sff.rs
index 2d04443..3f154e5 100644
--- a/src/sff.rs
+++ b/src/sff.rs
@@ -58,7 +58,17 @@ impl Encoding {
     fn compress(self, input: &[u8]) -> Vec<u8> {
         let mut out = Vec::new();
         match self {
-            Encoding::BitPerPix1 => todo!(),
+            Encoding::BitPerPix1 => {
+                assert!(input.len() % 8 == 0); // TODO not strictly necessary
+                for c in 0..input.len() / 8 {
+                    let mut byte = 0u8;
+                    for i in 0..8 {
+                        let piece = input[(c << 3) + i] >> 7;
+                        byte |= piece << (7 - i);
+                    }
+                    out.push(byte);
+                }
+            }
             Encoding::BitPerPix2 => todo!(),
             Encoding::BitPerPix4 => {
                 assert!(input.len() % 2 == 0); // TODO not strictly necessary
@@ -88,7 +98,7 @@ fn get_u32(input: &[u8], byte_offset: usize) -> u32 {
 }
 
 #[derive(Debug)]
-struct FileDesc<'a> {
+pub struct FileDesc<'a> {
     input: &'a [u8],
     char_width: usize,
     char_height: usize,
@@ -96,6 +106,9 @@ struct FileDesc<'a> {
     tables: Vec<Table>,
 }
 
+#[derive(Debug, Copy, Clone)]
+pub struct GlyphOffset(u32);
+
 impl<'a> FileDesc<'a> {
     fn bytes_per_codepoint(&self) -> usize {
         let px_per_codepoint = self.char_width * self.char_height;
@@ -107,7 +120,7 @@ impl<'a> FileDesc<'a> {
         }
     }
 
-    fn find_codepoint(&self, codepoint: u32) -> Option<&[u8]> {
+    pub fn find_codepoint(&self, codepoint: u32) -> Option<GlyphOffset> {
         self.tables
             .iter()
             .find(|tab| {
@@ -117,26 +130,55 @@ impl<'a> FileDesc<'a> {
             .map(|tab| {
                 let off = tab.offset as usize
                     + (codepoint - tab.first_codepoint) as usize * self.bytes_per_codepoint();
-                &self.input[off..off + self.bytes_per_codepoint()]
+                GlyphOffset(off as u32)
             })
     }
 
-    // input should be result of find_codepoint here
-    fn get_pixel_value(&self, input: &[u8], row: u8, col: u8) -> Option<u8> {
-        if row as usize >= self.char_height || col as usize >= self.char_width {
-            return None;
-        }
-        let px_index = row as usize * self.char_width + col as usize;
+    // returns the unscaled pixel value!
+    pub fn get_pixel_value_raw(&self, off: GlyphOffset, row: usize, col: usize) -> u8 {
+        assert!(row < self.char_height);
+        assert!(col < self.char_width);
+        let px_index = row * self.char_width + col;
         let Access {
             byte_index,
             shift,
             mask,
         } = self.encoding.access_from_index(px_index);
-        Some((input[byte_index] >> shift) & mask)
+        (self.input[off.0 as usize + byte_index] >> shift) & mask
+    }
+
+    pub fn get_pixel_value_scaled(&self, off: GlyphOffset, row: usize, col: usize) -> u8 {
+        let raw = self.get_pixel_value_raw(off, row, col);
+        match self.encoding {
+            Encoding::BitPerPix1 => raw * 255,
+            Encoding::BitPerPix2 => (raw as usize * 255 / 3) as u8,
+            Encoding::BitPerPix4 => (raw as usize * 255 / 15) as u8,
+            Encoding::BitPerPix8 => raw,
+        }
+    }
+
+    pub fn print_symbol(&self, off: GlyphOffset) {
+        println!("warning: assuming dark mode console");
+        let p100 = '█';
+        let p75 = '▓';
+        let p50 = '▒';
+        let p25 = '░';
+        let p0 = ' ';
+        let chars = [p0, p25, p50, p75, p100];
+
+        for row in 0..self.char_height {
+            for col in 0..self.char_width {
+                let value = self.get_pixel_value_scaled(off, row, col);
+                // map 0..=255 to 0..=4
+                let c = chars[value as usize * 4 / 255];
+                print!("{}{}", c, c);
+            }
+            println!();
+        }
     }
 }
 
-fn decode(input: &[u8]) -> FileDesc<'_> {
+pub fn decode(input: &[u8]) -> FileDesc<'_> {
     if input[0] != b's' || input[1] != b'f' || input[2] != b'f' || input[3] != b'\0' {
         panic!("invalid header magic");
     }