diff --git a/bingus/src/bin_/bytes.rs b/bingus/src/bin_/bytes.rs
index bdcc719..0b77a2c 100644
--- a/bingus/src/bin_/bytes.rs
+++ b/bingus/src/bin_/bytes.rs
@@ -1,4 +1,4 @@
-use std::convert::Infallible;
+use std::{borrow::Cow, convert::Infallible};
 
 use rayon::iter::{IntoParallelRefMutIterator, ParallelIterator};
 
@@ -27,8 +27,8 @@ impl TryFromDataBytes for Bytes {
 
 impl Bendable for Bytes {
     type Unit = u8;
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(mut self, f: F) -> Self {
-        self.par_iter_mut().for_each(|e| *e = f(e));
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(mut self, f: F) -> Self {
+        self.par_iter_mut().for_each(|e| *e = f(Cow::Borrowed(e)));
         self
     }
     fn format() -> crate::Format {
diff --git a/bingus/src/doc/pdf.rs b/bingus/src/doc/pdf.rs
index 81de293..dca00ab 100644
--- a/bingus/src/doc/pdf.rs
+++ b/bingus/src/doc/pdf.rs
@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use printpdf::{
     Op, PdfDocument, PdfPage, PdfParseErrorSeverity, PdfParseOptions, PdfSaveOptions, PdfWarnMsg,
 };
@@ -60,7 +62,7 @@ impl IntoDataBytes for PdfDocument {
 impl Bendable for PdfDocument {
     type Unit = Op;
 
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(self, f: F) -> Self {
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(self, f: F) -> Self {
         let PdfDocument {
             metadata,
             resources,
@@ -71,7 +73,11 @@ impl Bendable for PdfDocument {
             pages: pages
                 .into_iter()
                 .map(|page| PdfPage {
-                    ops: page.ops.into_iter().map(|op| f(&op)).collect::<Vec<Op>>(),
+                    ops: page
+                        .ops
+                        .into_iter()
+                        .map(|op| f(Cow::Owned(op)))
+                        .collect::<Vec<Op>>(),
                     ..page
                 })
                 .collect(),
@@ -108,7 +114,7 @@ mod tests {
         }
         assert_eq!(
             format!("{:?}", original),
-            format!("{:?}", original.clone().map(|u| u.clone()))
+            format!("{:?}", original.clone().map(|u| u.into_owned()))
         )
     }
 }
diff --git a/bingus/src/fnt/fontkit.rs b/bingus/src/fnt/fontkit.rs
index 3da11ac..caff993 100644
--- a/bingus/src/fnt/fontkit.rs
+++ b/bingus/src/fnt/fontkit.rs
@@ -1,6 +1,6 @@
 use font_kit::error::FontLoadingError;
 pub use font_kit::font::Font;
-use std::sync::Arc;
+use std::{borrow::Cow, sync::Arc};
 
 use crate::{Bendable, IntoDataBytes, TryFromDataBytes};
 
@@ -31,7 +31,7 @@ impl IntoDataBytes for Font {
 impl Bendable for Font {
     type Unit = u8;
 
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(self, f: F) -> Self {
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(self, f: F) -> Self {
         Self::try_from_data_bytes(self.into_data_bytes().map(f), (), Default::default())
             .expect("coudn't get font back from bytes after map")
     }
diff --git a/bingus/src/img/image.rs b/bingus/src/img/image.rs
index 0f47b2d..c91e359 100644
--- a/bingus/src/img/image.rs
+++ b/bingus/src/img/image.rs
@@ -1,4 +1,5 @@
 use std::{
+    borrow::Cow,
     convert::Infallible,
     iter::once,
     ops::{Add, Deref, DerefMut, Div, Mul, Sub},
@@ -177,8 +178,8 @@ where
     P: Send + Sync,
 {
     type Unit = P;
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(mut self, f: F) -> Self {
-        self.par_pixels_mut().for_each(|p| *p = f(p));
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(mut self, f: F) -> Self {
+        self.par_pixels_mut().for_each(|p| *p = f(Cow::Borrowed(p)));
         self
     }
     fn format() -> crate::Format {
diff --git a/bingus/src/lib.rs b/bingus/src/lib.rs
index fb89b3e..d4765fb 100644
--- a/bingus/src/lib.rs
+++ b/bingus/src/lib.rs
@@ -9,6 +9,7 @@ pub type Bytes = Vec<u8>;
 
 mod dynamic {
     use std::{
+        borrow::Cow,
         fs::File,
         io::{self, Read, Write},
         path::Path,
@@ -98,7 +99,7 @@ mod dynamic {
         type Unit = u8;
 
         /// /!\ may panic with io errors /!\
-        fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(mut self, f: F) -> Self {
+        fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(mut self, f: F) -> Self {
             let mut bytes = Vec::new();
             self.read_to_end(&mut bytes).expect("couldn't read file");
             self.write_all(&bytes.map(f)).expect("couldn't write file");
@@ -164,7 +165,7 @@ mod dynamic {
     }
 }
 
-use std::convert::Infallible;
+use std::{borrow::Cow, convert::Infallible};
 
 pub use dynamic::*;
 
@@ -184,7 +185,7 @@ pub trait Bendable: TryFromDataBytes + IntoDataBytes {
     ) -> Result<Self, <Self as TryFromDataBytes>::Error> {
         Self::try_from_data_bytes(b.into_data_bytes(), format, crop)
     }
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(self, f: F) -> Self;
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(self, f: F) -> Self;
     fn format() -> Format;
 }
 
diff --git a/bingus/src/snd/raw.rs b/bingus/src/snd/raw.rs
index 6b0bfb0..35ed099 100644
--- a/bingus/src/snd/raw.rs
+++ b/bingus/src/snd/raw.rs
@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use super::Sample;
 use derive_wrapper::{AsRef, From};
 use num::{
@@ -71,8 +73,8 @@ where
     for<'a> Vec<T>: IntoParallelRefMutIterator<'a, Item = &'a mut T>,
 {
     type Unit = T;
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(mut self, f: F) -> Self {
-        self.0.par_iter_mut().for_each(|e| *e = f(e));
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(mut self, f: F) -> Self {
+        self.0.par_iter_mut().for_each(|e| *e = f(Cow::Borrowed(e)));
         self
     }
     fn format() -> crate::dynamic::Format {
diff --git a/bingus/src/txt/bare.rs b/bingus/src/txt/bare.rs
index 92652a1..9cbb537 100644
--- a/bingus/src/txt/bare.rs
+++ b/bingus/src/txt/bare.rs
@@ -28,8 +28,11 @@ impl IntoDataBytes for Text<'_> {
 impl Bendable for Text<'_> {
     type Unit = char;
 
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(self, f: F) -> Self {
-        self.chars().map(|c| f(&c)).collect::<String>().into()
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(self, f: F) -> Self {
+        self.chars()
+            .map(|c| f(Cow::Owned(c)))
+            .collect::<String>()
+            .into()
     }
 
     fn format() -> crate::Format {
diff --git a/bingus/src/txt/shiva.rs b/bingus/src/txt/shiva.rs
index f6748f9..5b4c7bd 100644
--- a/bingus/src/txt/shiva.rs
+++ b/bingus/src/txt/shiva.rs
@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use derive_new::new;
 pub use shiva::core::DocumentType;
 use shiva::core::{bytes::Bytes, Document, Element};
@@ -47,12 +49,13 @@ impl IntoDataBytes for ShivaDocument {
 impl Bendable for ShivaDocument {
     type Unit = Element;
 
-    fn map<F: Fn(&Self::Unit) -> Self::Unit + Sync>(self, f: F) -> Self {
+    fn map<F: Fn(Cow<Self::Unit>) -> Self::Unit + Sync>(self, f: F) -> Self {
         ShivaDocument::new(
             Document::new(
                 self.document
                     .get_all_elements()
                     .into_iter()
+                    .map(Cow::Borrowed)
                     .map(f)
                     .collect(),
             ),