Add SubAssign, Add and Sub to Pixel trait requirements

proc_macros/src/lib.rs

@@ -26,6 +26,12 @@ fn impl_pixel(name: syn::Ident, fields: Vec<syn::Ident>) -> TokenStream {
             }
         }
 
+        impl std::ops::SubAssign for #name {
+            fn sub_assign(&mut self, other: Self) {
+                #( self.#fields -= other.#fields; )*
+            }
+        }
+
         impl std::ops::MulAssign<f32> for #name {
             fn mul_assign(&mut self, scalar: f32) {
                 #( self.#fields *= scalar; )*
@@ -38,6 +44,24 @@ fn impl_pixel(name: syn::Ident, fields: Vec<syn::Ident>) -> TokenStream {
             }
         }
 
+        impl std::ops::Add for #name {
+            type Output = Self;
+
+            fn add(mut self, other: Self) -> Self {
+                self += other;
+                self
+            }
+        }
+
+        impl std::ops::Sub for #name {
+            type Output = Self;
+
+            fn sub(mut self, other: Self) -> Self {
+                self -= other;
+                self
+            }
+        }
+
         impl std::ops::Mul<f32> for #name {
             type Output = Self;
 

src/image.rs

@@ -36,8 +36,11 @@ pub trait Format<P> {
 
 pub trait Pixel:
     std::ops::AddAssign
+    + std::ops::SubAssign
     + std::ops::MulAssign<f32>
     + std::ops::DivAssign<f32>
+    + std::ops::Add<Output = Self>
+    + std::ops::Sub<Output = Self>
     + std::ops::Mul<f32, Output = Self>
     + std::ops::Div<f32, Output = Self>
     + Clone
@@ -51,8 +54,11 @@ pub trait Pixel:
 
 impl<P> Pixel for P where
     P: std::ops::AddAssign
+        + std::ops::SubAssign
         + std::ops::MulAssign<f32>
         + std::ops::DivAssign<f32>
+        + std::ops::Add<Output = Self>
+        + std::ops::Sub<Output = Self>
         + std::ops::Mul<f32, Output = Self>
         + std::ops::Div<f32, Output = Self>
         + Clone