Add support for ASCII tags

src/decoder/ifd.rs

@@ -6,7 +6,7 @@ use std::collections::{HashMap};
 use super::stream::{ByteOrder, SmartReader, EndianReader};
 use ::{TiffError, TiffResult};
 
-use self::Value::{Unsigned, List, Rational};
+use self::Value::{Unsigned, List, Rational, Ascii};
 
 macro_rules! tags {
     {$(
@@ -33,7 +33,7 @@ macro_rules! tags {
 // Note: These tags appear in the order they are mentioned in the TIFF reference
 tags!{
     // Baseline tags:
-    Artist 315; // TODO add support
+    Artist 315;
     // grayscale images PhotometricInterpretation 1 or 3
     BitsPerSample 258;
     CellLength 265; // TODO add support
@@ -41,22 +41,22 @@ tags!{
     // palette-color images (PhotometricInterpretation 3)
     ColorMap 320; // TODO add support
     Compression 259; // TODO add support for 2 and 32773
-    Copyright 33_432; // TODO add support
-    DateTime 306; // TODO add support
+    Copyright 33_432;
+    DateTime 306;
     ExtraSamples 338; // TODO add support
     FillOrder 266; // TODO add support
     FreeByteCounts 289; // TODO add support
     FreeOffsets 288; // TODO add support
     GrayResponseCurve 291; // TODO add support
     GrayResponseUnit 290; // TODO add support
-    HostComputer 316; // TODO add support
-    ImageDescription 270; // TODO add support
+    HostComputer 316;
+    ImageDescription 270;
     ImageLength 257;
     ImageWidth 256;
-    Make 271; // TODO add support
+    Make 271;
     MaxSampleValue 281; // TODO add support
     MinSampleValue 280; // TODO add support
-    Model 272; // TODO add support
+    Model 272;
     NewSubfileType 254; // TODO add support
     Orientation 274; // TODO add support
     PhotometricInterpretation 262;
@@ -91,7 +91,8 @@ pub enum Value {
     //Signed(i32),
     Unsigned(u32),
     List(Vec<Value>),
-    Rational(u32, u32)
+    Rational(u32, u32),
+    Ascii(String)
 }
 
 impl Value {
@@ -113,8 +114,8 @@ impl Value {
                 Ok(new_vec)
             },
             Unsigned(val) => Ok(vec![val]),
-            Rational(numerator, denominator) => Ok(vec![numerator, denominator])
-            //_ => Err(::image::FormatError("Tag data malformed.".to_string()))
+            Rational(numerator, denominator) => Ok(vec![numerator, denominator]),
+            Ascii(val) => Ok(val.chars().map(|x| x as u32).collect())
         }
     }
 }
@@ -196,6 +197,11 @@ impl Entry {
                 }
                 Ok(List(v))
             },
+            (Type::ASCII, n) => {
+                try!(decoder.goto_offset(try!(self.r(bo).read_u32())));
+                let string = try!(decoder.read_string(n as usize));
+                Ok(Ascii(string))
+            }
             _ => Err(TiffError::UnsupportedError("Unsupported data type.".to_string()))
         }
     }

src/decoder/mod.rs

@@ -2,6 +2,7 @@ use std::io::{self, Read, Seek};
 use std::mem;
 use num_traits::{FromPrimitive, Num};
 use std::collections::HashMap;
+use std::string::FromUtf8Error;
 
 use ::{ColorType, TiffError, TiffResult};
 
@@ -279,6 +280,16 @@ impl<R: Read + Seek> Decoder<R> {
         self.reader.read_u32()
     }
 
+    /// Reads a string
+    #[inline]
+    pub fn read_string(&mut self, length: usize) -> Result<String, FromUtf8Error> {
+        let mut out = String::with_capacity(length);
+        self.reader.read_to_string(&mut out);
+        // Strings may be null-terminated, so we trim anything downstream of the null byte
+        let trimmed = out.bytes().take_while(|&n| n != 0).collect::<Vec<u8>>();
+        String::from_utf8(trimmed)
+    }
+
     /// Reads a TIFF IFA offset/value field
     #[inline]
     pub fn read_offset(&mut self) -> Result<[u8; 4], io::Error> {