Allow APNG with reductions disabled

src/lib.rs

@@ -32,6 +32,7 @@ use crate::png::PngImage;
 use crate::reduction::*;
 use log::{debug, info, trace, warn};
 use rayon::prelude::*;
+use std::borrow::Cow;
 use std::fmt;
 use std::fs::{copy, File, Metadata};
 use std::io::{stdin, stdout, BufWriter, Read, Write};
@@ -559,17 +560,30 @@ fn optimize_png(
     debug!("    IDAT size = {} bytes", idat_original_size);
     debug!("    File size = {} bytes", file_original_size);
 
+    // Check for APNG by presence of acTL chunk
+    let opts = if png.aux_chunks.iter().any(|c| &c.name == b"acTL") {
+        warn!("APNG detected, disabling all reductions");
+        let mut opts = opts.to_owned();
+        opts.interlace = None;
+        opts.bit_depth_reduction = false;
+        opts.color_type_reduction = false;
+        opts.palette_reduction = false;
+        opts.grayscale_reduction = false;
+        Cow::Owned(opts)
+    } else {
+        Cow::Borrowed(opts)
+    };
     let max_size = if opts.force {
         None
     } else {
         Some(png.estimated_output_size())
     };
-    if let Some(new_png) = optimize_raw(raw.clone(), opts, deadline, max_size) {
+    if let Some(new_png) = optimize_raw(raw.clone(), &opts, deadline, max_size) {
         png.raw = new_png.raw;
         png.idat_data = new_png.idat_data;
     }
 
-    postprocess_chunks(png, opts, &raw.ihdr);
+    postprocess_chunks(png, &opts, &raw.ihdr);
 
     let output = png.output();
 

src/png/mod.rs

@@ -93,8 +93,16 @@ impl PngData {
         let mut aux_chunks: Vec<Chunk> = Vec::new();
         while let Some(chunk) = parse_next_chunk(byte_data, &mut byte_offset, opts.fix_errors)? {
             match &chunk.name {
-                b"IDAT" => idat_data.extend_from_slice(chunk.data),
-                b"acTL" => return Err(PngError::APNGNotSupported),
+                b"IDAT" => {
+                    if idat_data.is_empty() {
+                        // Keep track of where the first IDAT sits relative to other chunks
+                        aux_chunks.push(Chunk {
+                            name: chunk.name,
+                            data: Vec::new(),
+                        })
+                    }
+                    idat_data.extend_from_slice(chunk.data);
+                }
                 b"IHDR" | b"PLTE" | b"tRNS" => {
                     key_chunks.insert(chunk.name, chunk.data.to_owned());
                 }
@@ -165,9 +173,10 @@ impl PngData {
         ihdr_data.write_all(&[0]).ok(); // Filter method -- 5-way adaptive filtering
         ihdr_data.write_all(&[self.raw.ihdr.interlaced as u8]).ok();
         write_png_block(b"IHDR", &ihdr_data, &mut output);
-        // Ancillary chunks
-        for chunk in self
-            .aux_chunks
+        // Ancillary chunks - split into those that come before IDAT and those that come after
+        let mut aux_split = self.aux_chunks.split(|c| &c.name == b"IDAT");
+        let aux_pre = aux_split.next().unwrap();
+        for chunk in aux_pre
             .iter()
             .filter(|c| !(&c.name == b"bKGD" || &c.name == b"hIST" || &c.name == b"tRNS"))
         {
@@ -202,15 +211,20 @@ impl PngData {
             _ => {}
         }
         // Special ancillary chunks that need to come after PLTE but before IDAT
-        for chunk in self
-            .aux_chunks
+        for chunk in aux_pre
             .iter()
             .filter(|c| &c.name == b"bKGD" || &c.name == b"hIST" || &c.name == b"tRNS")
         {
             write_png_block(&chunk.name, &chunk.data, &mut output);
         }
         // IDAT data
         write_png_block(b"IDAT", &self.idat_data, &mut output);
+        // Ancillary chunks that come after IDAT
+        for aux_post in aux_split {
+            for chunk in aux_post {
+                write_png_block(&chunk.name, &chunk.data, &mut output);
+            }
+        }
         // Stream end
         write_png_block(b"IEND", &[], &mut output);
 

tests/lib.rs

@@ -30,7 +30,7 @@ fn optimize_from_memory_apng() {
     in_file.read_to_end(&mut in_file_buf).unwrap();
 
     let result = oxipng::optimize_from_memory(&in_file_buf, &Options::default());
-    assert!(result.is_err());
+    assert!(result.is_ok());
 }
 
 #[test]
@@ -58,9 +58,9 @@ fn optimize_apng() {
     let result = oxipng::optimize(
         &"tests/files/apng_file.png".into(),
         &OutFile::Path(None),
-        &Options::default(),
+        &Options::from_preset(0),
     );
-    assert!(result.is_err());
+    assert!(result.is_ok());
 }
 
 #[test]