Recognize Photoshop 8BIM information

examples/check.rs

@@ -33,10 +33,67 @@ fn main() {
             frame.dispose,
             frame.needs_user_input
         );
+
+        reader.icc_profile().map(|icc| {
+            println!("  ICC profile: {} bytes", icc.len());
+        });
+
+        reader.xmp_metadata().map(|xmp| {
+            println!("  XMP metadata: {} bytes", xmp.len());
+        });
+
+        reader.photoshop_irb().map(|irb| {
+            println!("  Photoshop IRB: {} bytes", irb.len());
+            iterate_irb(irb);
+        });
     }
+
+    let _ = reader.next_frame_info();
+
+    reader.icc_profile().map(|icc| {
+        println!("  ICC profile: {} bytes", icc.len());
+    });
 }
 
 fn explain_usage() -> ! {
     println!("Print information on the frames of a gif.\n\nUsage: check <file>");
     process::exit(1)
 }
+
+fn iterate_irb(mut data: &[u8]) {
+    while data.len() >= 12 {
+        let signature = &data[0..4];
+        let key = u16::from_be_bytes(data[4..6].as_chunks::<2>().0[0]);
+
+        let identifier_len = data[6];
+        let identifier = &data[7..][..usize::from(identifier_len)];
+
+        let padded_len = (usize::from(identifier_len) + 1).div_ceil(2) * 2;
+        let length = u32::from_be_bytes(data[6..][padded_len..].as_chunks::<4>().0[0]) as usize;
+
+        if signature != b"8BIM" {
+            println!("   Invalid IRB signature: {:?}", signature);
+            return;
+        }
+
+        if data.len() < 12 + length {
+            println!("   Truncated IRB data");
+            return;
+        }
+
+        println!(
+            "   IRB block: key={:x}/{:?} length={}",
+            key,
+            str::from_utf8(identifier).unwrap_or("<invalid utf8>"),
+            length
+        );
+
+        if key == 0x3f8 {
+            println!("    (contains transfer functions)");
+            println!("    {:?}", &data[6 + padded_len + 4..][..length]);
+        }
+
+        let total_length = 6 + padded_len + 4 + length + (length % 2); // padded to even length
+        data = &data[total_length..];
+    }
+}

src/reader/mod.rs

@@ -259,15 +259,18 @@ impl<R: Read> ReadDecoder<R> {
 const EXT_NAME_NETSCAPE: &[u8] = b"NETSCAPE2.0";
 const EXT_NAME_XMP: &[u8] = b"XMP DataXMP";
 const EXT_NAME_ICC: &[u8] = b"ICCRGBG1012";
+const EXT_NAME_MAGICK_8BIM: &[u8] = b"MGK8BIM0000";
 
 /// State when parsing application extension
+#[derive(Debug)]
 enum AppExtensionState {
     /// Waiting for app name
     None,
     Netscape,
     Xmp,
     Icc,
     Skip,
+    Magick8Bim,
 }
 
 #[allow(dead_code)]
@@ -285,6 +288,8 @@ pub struct Decoder<R: Read> {
     xmp_metadata: Option<Vec<u8>>,
     /// ICC profile bytes.
     icc_profile: Option<Vec<u8>>,
+    /// 8BIM (Photoshop) profile bytes as encoded by imagemagick.
+    magick_8bim_profile: Option<Vec<u8>>,
 }
 
 impl<R> Decoder<R>
@@ -320,6 +325,7 @@ where
             app_extension_state: AppExtensionState::None,
             xmp_metadata: None,
             icc_profile: None,
+            magick_8bim_profile: None,
         }
     }
 
@@ -375,6 +381,10 @@ where
                         self.icc_profile = Some(Vec::new());
                         AppExtensionState::Icc
                     }
+                    EXT_NAME_MAGICK_8BIM => {
+                        self.magick_8bim_profile = Some(Vec::new());
+                        AppExtensionState::Magick8Bim
+                    }
                     _ => AppExtensionState::Skip,
                 }
             }
@@ -420,6 +430,12 @@ where
                     icc.extend_from_slice(data);
                 }
             }
+            AppExtensionState::Magick8Bim => {
+                if let Some(profile) = &mut self.magick_8bim_profile {
+                    self.memory_limit.try_reserve(profile, data.len())?;
+                    profile.extend_from_slice(data);
+                }
+            }
             AppExtensionState::Skip => {}
         };
         if is_last {
@@ -607,6 +623,15 @@ where
         self.icc_profile.as_deref()
     }
 
+    /// Photoshop Image Resource Block stored in the image.
+    #[inline]
+    #[must_use]
+    #[doc(alias = "8BIM")]
+    #[doc(alias = "image resource block")]
+    pub fn photoshop_irb(&self) -> Option<&[u8]> {
+        self.magick_8bim_profile.as_deref()
+    }
+
     /// Abort decoding and recover the `io::Read` instance
     pub fn into_inner(self) -> io::BufReader<R> {
         self.decoder.into_inner()