diff --git a/CHANGELOG.md b/CHANGELOG.md
index 01a0a3ad0..e94fbac03 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
  - Hide all modules from documentation, and only export the specific structures that should be public.
  Previously there were too many implementation details made public. The modules are still public for the purposes of our integration tests,
  but we strongly advice against using undocumented modules. These may become private in the future.
+ - Internal refactoring and code cleanup
 
 ### Version 0.18.3
  - Return exit code of 1 if an error occurred while processing a file using the CLI app ([#93](https://github.com/shssoichiro/oxipng/issues/93))
diff --git a/src/lib.rs b/src/lib.rs
index 15fa4a472..9f10369a8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -130,109 +130,128 @@ pub struct Options {
 
 impl Options {
     pub fn from_preset(level: u8) -> Options {
-        let mut opts = Options::default();
+        let opts = Options::default();
         match level {
-            0 => {
-                opts.idat_recoding = false;
-                let mut compression = HashSet::new();
-                compression.insert(3);
-                opts.compression = compression;
-            }
-            1 => {
-                let filter = HashSet::new();
-                opts.filter = filter;
-                let strategies = HashSet::new();
-                opts.strategies = strategies;
-                opts.use_heuristics = true;
-            }
-            // 2 is the default
-            3 => {
-                let mut filter = HashSet::new();
-                filter.insert(0);
-                filter.insert(5);
-                opts.filter = filter;
-                let mut compression = HashSet::new();
-                compression.insert(9);
-                opts.compression = compression;
-                let mut memory = HashSet::new();
-                for i in 8..10 {
-                    memory.insert(i);
-                }
-                opts.memory = memory;
-                let mut strategies = HashSet::new();
-                for i in 0..4 {
-                    strategies.insert(i);
-                }
-                opts.strategies = strategies;
-            }
-            4 => {
-                let mut filter = HashSet::new();
-                for i in 0..6 {
-                    filter.insert(i);
-                }
-                opts.filter = filter;
-                let mut compression = HashSet::new();
-                compression.insert(9);
-                opts.compression = compression;
-                let mut memory = HashSet::new();
-                for i in 8..10 {
-                    memory.insert(i);
-                }
-                opts.memory = memory;
-                let mut strategies = HashSet::new();
-                for i in 0..4 {
-                    strategies.insert(i);
-                }
-                opts.strategies = strategies;
-            }
-            5 => {
-                let mut filter = HashSet::new();
-                for i in 0..6 {
-                    filter.insert(i);
-                }
-                opts.filter = filter;
-                let mut compression = HashSet::new();
-                for i in 3..10 {
-                    compression.insert(i);
-                }
-                opts.compression = compression;
-                let mut memory = HashSet::new();
-                for i in 8..10 {
-                    memory.insert(i);
-                }
-                opts.memory = memory;
-                let mut strategies = HashSet::new();
-                for i in 0..4 {
-                    strategies.insert(i);
-                }
-                opts.strategies = strategies;
-            }
-            // Level 6
-            // If higher than 6, assume 6
-            _ => {
-                let mut filter = HashSet::new();
-                for i in 0..6 {
-                    filter.insert(i);
-                }
-                opts.filter = filter;
-                let mut compression = HashSet::new();
-                for i in 1..10 {
-                    compression.insert(i);
-                }
-                opts.compression = compression;
-                let mut memory = HashSet::new();
-                for i in 7..10 {
-                    memory.insert(i);
-                }
-                opts.memory = memory;
-                let mut strategies = HashSet::new();
-                for i in 0..4 {
-                    strategies.insert(i);
-                }
-                opts.strategies = strategies;
-            }
+            0 => opts.apply_preset_0(),
+            1 => opts.apply_preset_1(),
+            2 => opts.apply_preset_2(),
+            3 => opts.apply_preset_3(),
+            4 => opts.apply_preset_4(),
+            5 => opts.apply_preset_5(),
+            _ => opts.apply_preset_6(),
+        }
+    }
+
+    fn apply_preset_0(mut self) -> Self {
+        self.idat_recoding = false;
+        let mut compression = HashSet::new();
+        compression.insert(3);
+        self.compression = compression;
+        self
+    }
+
+    fn apply_preset_1(mut self) -> Self {
+        let filter = HashSet::new();
+        self.filter = filter;
+        let strategies = HashSet::new();
+        self.strategies = strategies;
+        self.use_heuristics = true;
+        self
+    }
+
+    fn apply_preset_2(self) -> Self {
+        self
+    }
+
+    fn apply_preset_3(mut self) -> Self {
+        let mut filter = HashSet::new();
+        filter.insert(0);
+        filter.insert(5);
+        self.filter = filter;
+        let mut compression = HashSet::new();
+        compression.insert(9);
+        self.compression = compression;
+        let mut memory = HashSet::new();
+        for i in 8..10 {
+            memory.insert(i);
+        }
+        self.memory = memory;
+        let mut strategies = HashSet::new();
+        for i in 0..4 {
+            strategies.insert(i);
+        }
+        self.strategies = strategies;
+        self
+    }
+
+    fn apply_preset_4(mut self) -> Self {
+        let mut filter = HashSet::new();
+        for i in 0..6 {
+            filter.insert(i);
+        }
+        self.filter = filter;
+        let mut compression = HashSet::new();
+        compression.insert(9);
+        self.compression = compression;
+        let mut memory = HashSet::new();
+        for i in 8..10 {
+            memory.insert(i);
+        }
+        self.memory = memory;
+        let mut strategies = HashSet::new();
+        for i in 0..4 {
+            strategies.insert(i);
+        }
+        self.strategies = strategies;
+        self
+    }
+
+    fn apply_preset_5(mut self) -> Self {
+        let mut filter = HashSet::new();
+        for i in 0..6 {
+            filter.insert(i);
+        }
+        self.filter = filter;
+        let mut compression = HashSet::new();
+        for i in 3..10 {
+            compression.insert(i);
+        }
+        self.compression = compression;
+        let mut memory = HashSet::new();
+        for i in 8..10 {
+            memory.insert(i);
+        }
+        self.memory = memory;
+        let mut strategies = HashSet::new();
+        for i in 0..4 {
+            strategies.insert(i);
+        }
+        self.strategies = strategies;
+        self
+    }
+
+    fn apply_preset_6(mut self) -> Self {
+        let mut filter = HashSet::new();
+        for i in 0..6 {
+            filter.insert(i);
+        }
+        self.filter = filter;
+        let mut compression = HashSet::new();
+        for i in 1..10 {
+            compression.insert(i);
+        }
+        self.compression = compression;
+        let mut memory = HashSet::new();
+        for i in 7..10 {
+            memory.insert(i);
+        }
+        self.memory = memory;
+        let mut strategies = HashSet::new();
+        for i in 0..4 {
+            strategies.insert(i);
         }
-        opts
+        self.strategies = strategies;
+        self
     }
 }
 
diff --git a/src/png.rs b/src/png.rs
index 883bbc91b..759a7dd23 100644
--- a/src/png.rs
+++ b/src/png.rs
@@ -184,7 +184,7 @@ pub struct PngData {
 impl PngData {
     /// Create a new `PngData` struct by opening a file
     #[inline]
-    #[cfg(test)]
+    #[allow(dead_code)]
     pub fn new(filepath: &Path, fix_errors: bool) -> Result<PngData, PngError> {
         let byte_data = PngData::read_file(filepath)?;