diff --git a/src/main.rs b/src/main.rs
index 69ed9a1..7e88e12 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -92,7 +92,55 @@ impl<'input, I> Iterator for Decoder<I> where I: Iterator<Item=u8> {
 
     fn next(&mut self) -> Option<Self::Item> {
         let byte = self.bytes.next()?;
-        todo!();
+        match byte {
+            QOI_OP_RGB => {
+                return Some(PixelRGBA {
+                    r: self.bytes.next()?,
+                    g: self.bytes.next()?,
+                    b: self.bytes.next()?,
+                    a: self.prev_pixel.a,
+                });
+            },
+            QOI_OP_RGBA => {
+                return Some(PixelRGBA {
+                    r: self.bytes.next()?,
+                    g: self.bytes.next()?,
+                    b: self.bytes.next()?,
+                    a: self.bytes.next()?,
+                });
+            },
+            QOI_OP_INDEX => {
+                let idx = (byte | 0b0011_1111) as usize;
+                return Some(self.back_buffer[idx]);
+            },
+            QOI_OP_DIFF => {
+                let dr = ((byte | 0b0011_0000) >> 4) - 2;
+                let dg = ((byte | 0b0000_1100) >> 2) - 2;
+                let db = (byte | 0b0000_0011) - 2;
+                return Some(PixelRGBA {
+                    r: self.prev_pixel.r + dr,
+                    g: self.prev_pixel.g + dg,
+                    b: self.prev_pixel.b + db,
+                    a: self.prev_pixel.a
+                });
+            },
+            QOI_OP_LUMA => {
+                let dg = (byte | 0b0011_1111) - 32;
+                let packed = self.bytes.next()?;
+                let drdg = ((packed | 0b1111_0000) >> 4) - 8;
+                let dbdg = (packed | 0b0000_1111) - 8;
+                let dr = drdg + dg;
+                let db = dbdg + dg;
+                return Some(PixelRGBA {
+                    r: self.prev_pixel.r + dr,
+                    g: self.prev_pixel.g + dg,
+                    b: self.prev_pixel.b + db,
+                    a: self.prev_pixel.a
+                });
+            },
+            QOI_OP_RUN => {todo!("Impl Decode QOI_OP_RUN")},
+            _ => {panic!("bad op code")}
+        }
     }
 }