fixed rotation issues + updated readme

rustitch/src/exp.rs

@@ -42,7 +42,7 @@ pub fn parse(data: &[u8]) -> Result<Vec<StitchCommand>, Error> {
                         break;
                     }
                     let dx = data[i] as i8 as i16;
-                    let dy = data[i + 1] as i8 as i16;
+                    let dy = -(data[i + 1] as i8 as i16);
                     commands.push(StitchCommand::Jump { dx, dy });
                     i += 2;
                 }
@@ -53,7 +53,7 @@ pub fn parse(data: &[u8]) -> Result<Vec<StitchCommand>, Error> {
             }
         } else {
             let dx = b1 as i8 as i16;
-            let dy = b2 as i8 as i16;
+            let dy = -(b2 as i8 as i16);
             commands.push(StitchCommand::Stitch { dx, dy });
             i += 2;
         }
@@ -88,8 +88,8 @@ mod tests {
     fn parse_simple_stitches() {
         let data = [0x0A, 0x14, 0x05, 0x03];
         let cmds = parse(&data).unwrap();
-        assert!(matches!(cmds[0], StitchCommand::Stitch { dx: 10, dy: 20 }));
-        assert!(matches!(cmds[1], StitchCommand::Stitch { dx: 5, dy: 3 }));
+        assert!(matches!(cmds[0], StitchCommand::Stitch { dx: 10, dy: -20 }));
+        assert!(matches!(cmds[1], StitchCommand::Stitch { dx: 5, dy: -3 }));
         assert!(matches!(cmds[2], StitchCommand::End));
     }
 
@@ -98,10 +98,7 @@ mod tests {
         // -10 as i8 = 0xF6, -20 as i8 = 0xEC
         let data = [0xF6, 0xEC];
         let cmds = parse(&data).unwrap();
-        assert!(matches!(
-            cmds[0],
-            StitchCommand::Stitch { dx: -10, dy: -20 }
-        ));
+        assert!(matches!(cmds[0], StitchCommand::Stitch { dx: -10, dy: 20 }));
     }
 
     #[test]
@@ -110,14 +107,14 @@ mod tests {
         let cmds = parse(&data).unwrap();
         assert!(matches!(cmds[0], StitchCommand::Stitch { .. }));
         assert!(matches!(cmds[1], StitchCommand::ColorChange));
-        assert!(matches!(cmds[2], StitchCommand::Stitch { dx: 5, dy: 3 }));
+        assert!(matches!(cmds[2], StitchCommand::Stitch { dx: 5, dy: -3 }));
     }
 
     #[test]
     fn parse_jump() {
         let data = [0x80, 0x04, 0x0A, 0x14];
         let cmds = parse(&data).unwrap();
-        assert!(matches!(cmds[0], StitchCommand::Jump { dx: 10, dy: 20 }));
+        assert!(matches!(cmds[0], StitchCommand::Jump { dx: 10, dy: -20 }));
     }
 
     #[test]