From fb30648c12a774e9a4603a77ab83b38c4a5f0878 Mon Sep 17 00:00:00 2001
From: Birk Tjelmeland <birktjelmeland@yahoo.no>
Date: Thu, 31 Jan 2019 21:20:49 +0100
Subject: [PATCH] Implemented basic tiff encoding

---
 src/decoder/ifd.rs    |   6 +
 src/encoder/mod.rs    | 264 ++++++++++++++++++++++++++++++++++++++++++
 src/encoder/writer.rs |  92 +++++++++++++++
 src/lib.rs            |   1 +
 4 files changed, 363 insertions(+)
 create mode 100644 src/encoder/mod.rs
 create mode 100644 src/encoder/writer.rs

diff --git a/src/decoder/ifd.rs b/src/decoder/ifd.rs
index 3679e51..515006e 100644
--- a/src/decoder/ifd.rs
+++ b/src/decoder/ifd.rs
@@ -26,6 +26,12 @@ macro_rules! tags {
                     Tag::Unknown(n)
                 }
             }
+            pub fn to_u16(&self) -> u16 {
+                match self {
+                    $( Tag::$tag => $val, )*
+                    Tag::Unknown(n) => *n,
+                }
+            }
         }
     }
 }
diff --git a/src/encoder/mod.rs b/src/encoder/mod.rs
new file mode 100644
index 0000000..f0a197e
--- /dev/null
+++ b/src/encoder/mod.rs
@@ -0,0 +1,264 @@
+mod writer;
+use self::writer::*;
+use std::io::{self, Write, Seek};
+use crate::decoder::ifd;
+use std::collections::{BTreeMap, HashMap};
+
+pub struct Rational {
+    pub n: u32,
+    pub d: u32,
+}
+
+pub trait IfdType {
+    type Inner;
+    fn byte_len() -> u32;
+    fn field_type() -> u16;
+    fn count(&self) -> u32;
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error>;
+}
+
+impl IfdType for [u8] {
+    type Inner = u8;
+    fn byte_len() -> u32 {
+        1
+    }
+    fn field_type() -> u16 {
+        1
+    }
+    fn count(&self) -> u32 {
+        self.len() as u32
+    }
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error> {
+        for x in self {
+            writer.write_u8(*x)?;
+        }
+        Ok(())
+    }
+}
+
+impl IfdType for [u16] {
+    type Inner = u16;
+    fn byte_len() -> u32 {
+        2
+    }
+    fn field_type() -> u16 {
+        3
+    }
+    fn count(&self) -> u32 {
+        self.len() as u32
+    }
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error> {
+        for x in self {
+            writer.write_u16(*x)?;
+        }
+        Ok(())
+    }
+}
+
+impl IfdType for [u32] {
+    type Inner = u32;
+    fn byte_len() -> u32 {
+        4
+    }
+    fn field_type() -> u16 {
+        4
+    }
+    fn count(&self) -> u32 {
+        self.len() as u32
+    }
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error> {
+        for x in self {
+            writer.write_u32(*x)?;
+        }
+        Ok(())
+    }
+}
+
+impl IfdType for [Rational] {
+    type Inner = Rational;
+    fn byte_len() -> u32 {
+        8
+    }
+    fn field_type() -> u16 {
+        5
+    }
+    fn count(&self) -> u32 {
+        self.len() as u32
+    }
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error> {
+        for x in self {
+            writer.write_u32(x.n)?;
+            writer.write_u32(x.d)?;
+        }
+        Ok(())
+    }
+}
+
+impl IfdType for [i8] {
+    type Inner = i8;
+    fn byte_len() -> u32 {
+        1
+    }
+    fn field_type() -> u16 {
+        6
+    }
+    fn count(&self) -> u32 {
+        self.len() as u32
+    }
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error> {
+        for x in self {
+            writer.write_u8(*x as u8)?;
+        }
+        Ok(())
+    }
+}
+
+impl IfdType for str {
+    type Inner = u8;
+    fn byte_len() -> u32 {
+        1
+    }
+    fn field_type() -> u16 {
+        2
+    }
+    fn count(&self) -> u32 {
+        self.len() as u32
+    }
+    fn write<W: Write>(&self, writer: &mut TiffWriter<W>) -> Result<(), io::Error> {
+        for x in self.chars() {
+            if x.is_ascii() {
+                writer.write_u8(x as u8)?;
+            }
+        }
+        writer.write_u8(0)?;
+        Ok(())
+    }
+}
+
+pub struct TiffEncoder<W> {
+    writer: TiffWriter<W>,
+    // Sort tags by ascending order
+    ifd: BTreeMap<u16, (u16, u32, Vec<u8>)>,
+    ifd_offsets: HashMap<u16, u32>,
+    strip_number: u32,
+}
+
+impl<W: Write + Seek> TiffEncoder<W> {
+    pub fn new_le(writer: W) -> TiffEncoder<W> {
+        TiffEncoder {
+            writer: TiffWriter::new_le(writer),
+            ifd: BTreeMap::new(),
+            ifd_offsets: HashMap::new(),
+            strip_number: 0,
+        }
+    }
+
+    pub fn new_be(writer: W) -> TiffEncoder<W> {
+        TiffEncoder {
+            writer: TiffWriter::new_be(writer),
+            ifd: BTreeMap::new(),
+            ifd_offsets: HashMap::new(),
+            strip_number: 0,
+        }
+    }
+
+    pub fn write_header(&mut self) -> Result<(), io::Error> {
+        match self.writer.byte_order() {
+            ByteOrder::LittleEndian => self.writer.write_u16(0x4949)?,
+            ByteOrder::BigEndian => self.writer.write_u16(0x4d4d)?,
+        };
+        self.writer.write_u16(42)?;
+
+        Ok(())
+    }
+
+    pub fn new_ifd(&mut self) -> Result<(), io::Error> {
+        self.writer.pad_word_boundary()?;
+        let offset = self.writer.offset();
+        self.writer.write_u32(offset + 4)?;
+
+        self.ifd = BTreeMap::new();
+
+        Ok(())
+    }
+
+    pub fn new_ifd_entry<T: IfdType + ?Sized>(&mut self, tag: ifd::Tag, value: &T) {
+        let mut bytes: Vec<u8> = Vec::new();
+        {
+            let mut writer = TiffWriter::new(&mut bytes, self.writer.byte_order());
+            value.write(&mut writer).unwrap();
+        }
+        self.ifd.insert(tag.to_u16(), (<T>::field_type(), value.count(), bytes));
+    }
+
+    pub fn finish_ifd(&mut self) -> Result<(), io::Error> {
+        self.ifd_offsets = HashMap::new();
+        self.writer.write_u16(self.ifd.len() as u16)?;
+
+        let mut value_offset = self.writer.offset() + self.ifd.len() as u32 * 12 + 4;
+
+        {
+            let mut ifd_values = Vec::new();
+
+            for (tag, (type_, count, bytes)) in &self.ifd {
+                self.writer.write_u16(*tag)?;
+                self.writer.write_u16(*type_)?;
+                self.writer.write_u32(*count)?;
+                if bytes.len() <= 4 {
+                    self.ifd_offsets.insert(*tag, self.writer.offset());
+                    self.writer.write_bytes(bytes)?;
+                    for _ in 0..4 - bytes.len() {
+                        self.writer.write_u8(0)?;
+                    }
+                }
+                else {
+                    self.ifd_offsets.insert(*tag, value_offset);
+                    self.writer.write_u32(value_offset)?;
+                    ifd_values.push(bytes);
+                    value_offset += bytes.len() as u32;
+                }
+            }
+
+            self.writer.write_u32(0)?;
+
+            for value in ifd_values {
+                self.writer.write_bytes(value)?;
+            }
+        }
+
+        self.ifd = BTreeMap::new();
+
+        Ok(())
+    }
+
+    pub fn update_ifd_value<T: IfdType + ?Sized>(&mut self, tag: ifd::Tag, idx: u32, value: &T) -> Result<(), io::Error> {
+        if let Some(off) = self.ifd_offsets.get(&tag.to_u16()) {
+            let curr_offset = self.writer.offset();
+            self.writer.too_offset(off + idx * <T>::byte_len())?;
+            value.write(&mut self.writer)?;
+            self.writer.too_offset(curr_offset)?;
+        }
+
+        Ok(())
+    }
+
+    pub fn write_strip(&mut self, strip_value: &[u8]) -> Result<(), io::Error> {
+        let offset = self.writer.offset();
+        self.writer.write_bytes(strip_value)?;
+
+        let n = self.strip_number;
+
+        self.update_ifd_value::<[u32]>(ifd::Tag::StripOffsets, n, &[offset])?;
+        self.update_ifd_value::<[u32]>(ifd::Tag::StripByteCounts, n, &[strip_value.len() as u32])?;
+
+        Ok(())
+    }
+}
+
+pub struct IfdEncoder<'a, W> {
+    tiff_encoder: &'a mut TiffEncoder<W>,
+}
+
+pub struct ImageEncoder<'a, W> {
+    tiff_encoder: &'a mut TiffEncoder<W>,
+}
diff --git a/src/encoder/writer.rs b/src/encoder/writer.rs
new file mode 100644
index 0000000..1e4ac10
--- /dev/null
+++ b/src/encoder/writer.rs
@@ -0,0 +1,92 @@
+use std::io::{self, Write, Seek, SeekFrom};
+use byteorder::{WriteBytesExt, BigEndian, LittleEndian};
+
+/// Byte order of the TIFF file.
+#[derive(Clone, Copy, Debug)]
+pub enum ByteOrder {
+    /// little endian byte order
+    LittleEndian,
+    /// big endian byte order
+    BigEndian
+}
+
+pub struct TiffWriter<W> {
+    writer: W,
+    byte_order: ByteOrder,
+    offset: u32,
+}
+
+impl<W: Write> TiffWriter<W> {
+    pub fn new(writer: W, byte_order: ByteOrder) -> Self {
+        Self {
+            writer,
+            byte_order,
+            offset: 0,
+        }
+    }
+    pub fn new_le(writer: W) -> Self {
+        Self::new(writer, ByteOrder::LittleEndian)
+    }
+
+    pub fn new_be(writer: W) -> Self {
+        Self::new(writer, ByteOrder::BigEndian)
+    }
+
+    pub fn byte_order(&self) -> ByteOrder {
+        self.byte_order
+    }
+
+    pub fn offset(&self) -> u32 {
+        self.offset
+    }
+
+    pub fn write_bytes(&mut self, bytes: &[u8]) -> Result<(), io::Error> {
+        self.writer.write_all(bytes)?;
+        self.offset += bytes.len() as u32;
+        Ok(())
+    }
+
+    pub fn write_u8(&mut self, n: u8) -> Result<(), io::Error> {
+        self.writer.write_u8(n)?;
+        self.offset += 1;
+        Ok(())
+    }
+
+    pub fn write_u16(&mut self, n: u16) -> Result<(), io::Error> {
+        match self.byte_order {
+            ByteOrder::LittleEndian => self.writer.write_u16::<LittleEndian>(n),
+            ByteOrder::BigEndian => self.writer.write_u16::<BigEndian>(n),
+        }?;
+
+        self.offset += 2;
+
+        Ok(())
+    }
+
+    pub fn write_u32(&mut self, n: u32) -> Result<(), io::Error> {
+        match self.byte_order {
+            ByteOrder::LittleEndian => self.writer.write_u32::<LittleEndian>(n),
+            ByteOrder::BigEndian => self.writer.write_u32::<BigEndian>(n),
+        }?;
+        
+        self.offset += 4;
+
+        Ok(())
+    }
+
+    pub fn pad_word_boundary(&mut self) -> Result<(), io::Error> {
+        while self.offset % 4 != 0 {
+            self.writer.write_u8(0)?;
+        }
+    
+        Ok(())
+    }
+}
+
+impl<W: Seek> TiffWriter<W> {
+    pub fn too_offset(&mut self, offset: u32) -> Result<(), io::Error> {
+        self.offset = offset;
+        self.writer.seek(SeekFrom::Start(offset as u64))?;
+        Ok(())
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 2722a90..bf4a1bb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,6 +12,7 @@ extern crate lzw;
 extern crate num_traits;
 
 pub mod decoder;
+pub mod encoder;
 mod error;
 
 pub use self::error::{TiffError, TiffFormatError, TiffUnsupportedError, TiffResult};