From 76d24ff2267cf8c9653a89a8fe7285e632c902ea Mon Sep 17 00:00:00 2001
From: Andrew <andrew@digerati.co.nz>
Date: Sun, 2 Feb 2025 22:38:31 +1300
Subject: [PATCH] Use chunks_exact

---
 src/filters.rs             | 4 ++--
 src/headers.rs             | 2 +-
 src/reduction/alpha.rs     | 6 +++---
 src/reduction/bit_depth.rs | 6 +++---
 src/reduction/color.rs     | 2 +-
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/filters.rs b/src/filters.rs
index e1074ed5..d0b03b1d 100644
--- a/src/filters.rs
+++ b/src/filters.rs
@@ -126,8 +126,8 @@ impl RowFilter {
             return;
         }
 
-        let mut pixels: Vec<_> = data.chunks_mut(bpp).collect();
-        let prev_pixels: Vec<_> = prev_line.chunks(bpp).collect();
+        let mut pixels: Vec<_> = data.chunks_exact_mut(bpp).collect();
+        let prev_pixels: Vec<_> = prev_line.chunks_exact(bpp).collect();
         for i in 0..pixels.len() {
             if pixels[i].iter().skip(color_bytes).all(|b| *b == 0) {
                 // If the first pixel in the row is transparent, find the next non-transparent pixel and pretend
diff --git a/src/headers.rs b/src/headers.rs
index 1c3860a4..cf447ed0 100644
--- a/src/headers.rs
+++ b/src/headers.rs
@@ -225,7 +225,7 @@ fn palette_to_rgba(
 ) -> Result<Vec<RGBA8>, PngError> {
     let palette_data = palette_data.ok_or_else(|| PngError::new("no palette in indexed image"))?;
     let mut palette: Vec<_> = palette_data
-        .chunks(3)
+        .chunks_exact(3)
         .map(|color| RGBA8::new(color[0], color[1], color[2], 255))
         .collect();
 
diff --git a/src/reduction/alpha.rs b/src/reduction/alpha.rs
index 9e17be9e..04527cfd 100644
--- a/src/reduction/alpha.rs
+++ b/src/reduction/alpha.rs
@@ -17,7 +17,7 @@ pub fn cleaned_alpha_channel(png: &PngImage) -> Option<PngImage> {
     let colored_bytes = bpp - byte_depth;
 
     let mut reduced = Vec::with_capacity(png.data.len());
-    for pixel in png.data.chunks(bpp) {
+    for pixel in png.data.chunks_exact(bpp) {
         if pixel.iter().skip(colored_bytes).all(|b| *b == 0) {
             reduced.resize(reduced.len() + bpp, 0);
         } else {
@@ -46,7 +46,7 @@ pub fn reduced_alpha_channel(png: &PngImage, optimize_alpha: bool) -> Option<Png
     let mut has_transparency = false;
     let mut used_colors = vec![false; 256];
 
-    for pixel in png.data.chunks(bpp) {
+    for pixel in png.data.chunks_exact(bpp) {
         if optimize_alpha && pixel.iter().skip(colored_bytes).all(|b| *b == 0) {
             // Fully transparent, we may be able to reduce with tRNS
             has_transparency = true;
@@ -75,7 +75,7 @@ pub fn reduced_alpha_channel(png: &PngImage, optimize_alpha: bool) -> Option<Png
     };
 
     let mut raw_data = Vec::with_capacity(png.data.len());
-    for pixel in png.data.chunks(bpp) {
+    for pixel in png.data.chunks_exact(bpp) {
         match transparency_pixel {
             Some(trns) if pixel.iter().skip(colored_bytes).all(|b| *b == 0) => {
                 raw_data.resize(raw_data.len() + colored_bytes, trns);
diff --git a/src/reduction/bit_depth.rs b/src/reduction/bit_depth.rs
index ee8b6314..caa83980 100644
--- a/src/reduction/bit_depth.rs
+++ b/src/reduction/bit_depth.rs
@@ -16,13 +16,13 @@ pub fn reduced_bit_depth_16_to_8(png: &PngImage, force_scale: bool) -> Option<Pn
     }
 
     // Reduce from 16 to 8 bits per channel per pixel
-    if png.data.chunks(2).any(|pair| pair[0] != pair[1]) {
+    if png.data.chunks_exact(2).any(|pair| pair[0] != pair[1]) {
         // Can't reduce
         return None;
     }
 
     Some(PngImage {
-        data: png.data.iter().step_by(2).copied().collect(),
+        data: png.data.chunks_exact(2).map(|pair| pair[0]).collect(),
         ihdr: IhdrData {
             color_type: png.ihdr.color_type.clone(),
             bit_depth: BitDepth::Eight,
@@ -41,7 +41,7 @@ pub fn scaled_bit_depth_16_to_8(png: &PngImage) -> Option<PngImage> {
     // Reduce from 16 to 8 bits per channel per pixel by scaling when necessary
     let data = png
         .data
-        .chunks(2)
+        .chunks_exact(2)
         .map(|pair| {
             if pair[0] == pair[1] {
                 return pair[0];
diff --git a/src/reduction/color.rs b/src/reduction/color.rs
index fe11d048..ddf40234 100644
--- a/src/reduction/color.rs
+++ b/src/reduction/color.rs
@@ -106,7 +106,7 @@ pub fn reduced_rgb_to_grayscale(png: &PngImage) -> Option<PngImage> {
     let byte_depth = png.bytes_per_channel();
     let bpp = png.channels_per_pixel() * byte_depth;
     let last_color = 2 * byte_depth;
-    for pixel in png.data.chunks(bpp) {
+    for pixel in png.data.chunks_exact(bpp) {
         if byte_depth == 1 {
             if pixel[0] != pixel[1] || pixel[1] != pixel[2] {
                 return None;