Somehow the current offset was invalid when using multipage images. Now using the seek function to get the current offset

src/encoder/writer.rs

@@ -10,7 +10,6 @@ impl TiffByteOrder for LittleEndian {
     fn write_header<W: Write>(writer: &mut TiffWriter<W>) -> TiffResult<()> {
         writer.writer.write_u16::<LittleEndian>(0x4949)?;
         writer.writer.write_u16::<LittleEndian>(42)?;
-        writer.offset += 4;
 
         Ok(())
     }
@@ -20,7 +19,6 @@ impl TiffByteOrder for BigEndian {
     fn write_header<W: Write>(writer: &mut TiffWriter<W>) -> TiffResult<()> {
         writer.writer.write_u16::<BigEndian>(0x4d4d)?;
         writer.writer.write_u16::<BigEndian>(42)?;
-        writer.offset += 4;
 
         Ok(())
     }
@@ -28,75 +26,66 @@ impl TiffByteOrder for BigEndian {
 
 pub struct TiffWriter<W> {
     writer: W,
-    offset: u64,
 }
 
 impl<W: Write> TiffWriter<W> {
     pub fn new(writer: W) -> Self {
-        Self { writer, offset: 0 }
-    }
-
-    pub fn offset(&self) -> u64 {
-        self.offset
+        Self { writer }
     }
 
     pub fn write_bytes(&mut self, bytes: &[u8]) -> Result<(), io::Error> {
         self.writer.write_all(bytes)?;
-        self.offset += bytes.len() as u64;
         Ok(())
     }
 
     pub fn write_u8(&mut self, n: u8) -> Result<(), io::Error> {
         self.writer.write_u8(n)?;
-        self.offset += 1;
         Ok(())
     }
 
     pub fn write_i8(&mut self, n: i8) -> Result<(), io::Error> {
         self.writer.write_i8(n)?;
-        self.offset += 1;
         Ok(())
     }
 
     pub fn write_u16(&mut self, n: u16) -> Result<(), io::Error> {
         self.writer.write_u16::<NativeEndian>(n)?;
-        self.offset += 2;
 
         Ok(())
     }
 
     pub fn write_i16(&mut self, n: i16) -> Result<(), io::Error> {
         self.writer.write_i16::<NativeEndian>(n)?;
-        self.offset += 2;
 
         Ok(())
     }
 
     pub fn write_u32(&mut self, n: u32) -> Result<(), io::Error> {
         self.writer.write_u32::<NativeEndian>(n)?;
-        self.offset += 4;
 
         Ok(())
     }
 
     pub fn write_i32(&mut self, n: i32) -> Result<(), io::Error> {
         self.writer.write_i32::<NativeEndian>(n)?;
-        self.offset += 4;
 
         Ok(())
     }
 
     pub fn write_u64(&mut self, n: u64) -> Result<(), io::Error> {
         self.writer.write_u64::<NativeEndian>(n)?;
-        self.offset += 8;
 
         Ok(())
     }
 
+}
+
+impl<W: Write + Seek> TiffWriter<W> {
     pub fn pad_word_boundary(&mut self) -> Result<(), io::Error> {
-        if self.offset % 4 != 0 {
+        let offset = self.offset();
+        if offset % 4 != 0 {
             let padding = [0, 0, 0];
-            let padd_len = 4 - (self.offset % 4);
+            let padd_len = 4 - (offset % 4);
             self.writer.write_all(&padding[..padd_len as usize])?;
         }
 
@@ -106,8 +95,11 @@ impl<W: Write> TiffWriter<W> {
 
 impl<W: Seek> TiffWriter<W> {
     pub fn goto_offset(&mut self, offset: u64) -> Result<(), io::Error> {
-        self.offset = offset;
         self.writer.seek(SeekFrom::Start(offset as u64))?;
         Ok(())
     }
+
+    pub fn offset(&mut self) -> u64 {
+        self.writer.seek(SeekFrom::Current(0)).unwrap()
+    }
 }