From 73f8aad65d30db45cd98abb8544501b096289806 Mon Sep 17 00:00:00 2001
From: Andrew <andrew@digerati.co.nz>
Date: Tue, 1 Aug 2023 08:14:24 +1200
Subject: [PATCH] Check idat_recoding for all recompression

---
 src/lib.rs  | 28 +++++++++++++++-------------
 src/main.rs |  2 +-
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index ae3b93ef..bde4deed 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -180,7 +180,7 @@ pub struct Options {
     ///
     /// Default: `true`
     pub grayscale_reduction: bool,
-    /// Whether to perform IDAT recoding
+    /// Whether to perform recoding of IDAT and other compressed chunks
     ///
     /// If any type of reduction is performed, IDAT recoding will be performed
     /// regardless of this setting
@@ -904,23 +904,25 @@ fn postprocess_chunks(
                 None
             };
             // sRGB-like profile can be replaced with an sRGB chunk with the same rendering intent
-            // Otherwise try recompressing the profile
             if let Some(intent) = intent {
                 trace!("Replacing iCCP chunk with equivalent sRGB chunk");
                 png.aux_chunks[iccp_idx] = Chunk {
                     name: *b"sRGB",
                     data: vec![intent],
                 };
-            } else if let Ok(iccp) = construct_iccp(&icc, opts.deflate) {
-                let cur_len = png.aux_chunks[iccp_idx].data.len();
-                let new_len = iccp.data.len();
-                if new_len < cur_len {
-                    debug!(
-                        "Recompressed iCCP chunk: {} ({} bytes decrease)",
-                        new_len,
-                        cur_len - new_len
-                    );
-                    png.aux_chunks[iccp_idx] = iccp;
+            } else if opts.idat_recoding {
+                // Try recompressing the profile
+                if let Ok(iccp) = construct_iccp(&icc, opts.deflate) {
+                    let cur_len = png.aux_chunks[iccp_idx].data.len();
+                    let new_len = iccp.data.len();
+                    if new_len < cur_len {
+                        debug!(
+                            "Recompressed iCCP chunk: {} ({} bytes decrease)",
+                            new_len,
+                            cur_len - new_len
+                        );
+                        png.aux_chunks[iccp_idx] = iccp;
+                    }
                 }
             }
         }
@@ -950,7 +952,7 @@ fn postprocess_chunks(
         .iter_mut()
         .filter(|c| &c.name == b"fdAT")
         .collect();
-    if !fdat.is_empty() {
+    if opts.idat_recoding && !fdat.is_empty() {
         let buffer_size = orig_ihdr.raw_data_size();
         fdat.par_iter_mut()
             .with_max_len(1)
diff --git a/src/main.rs b/src/main.rs
index f2166785..d1b45465 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -231,7 +231,7 @@ fn main() {
         )
         .arg(
             Arg::new("no-recoding")
-                .help("No IDAT recoding unless necessary")
+                .help("No recoding of IDAT or other compressed chunks unless necessary")
                 .long("nz")
                 .action(ArgAction::SetTrue),
         )