refactor dct and quality

src/descriptors/mod.rs

@@ -13,22 +13,25 @@ pub trait Descriptor {
 
 /// Interprets a 64-element array as an 8x8 matrix
 /// returns a nicely printable string
-fn print_matrix<T: ToString>(array: [T; 64]) -> String {
+fn print_matrix<T: ToString + std::fmt::Display>(array: [T; 64]) -> String {
     let mut output = String::new();
     for x in 0..8 {
         for y in 0..8 {
-            output.push_str(&array[x*8+y].to_string());
-            output.push_str(",\t");
+            let element = format!("{:.2}", &array[x*8+y]);
+            let element = format!("{:8}\t", element);
+            output.push_str(&element);
         }
         output.push('\n');
     }
     output
 }
 
+/// A struct representing a Discrete Cosine Transform descriptor
+/// Transforms an image into an 8x8 grayscale version, and transforms it
+/// into the frequency domain
 pub struct DCT {
-    quantization_matrix: [u8; 64],
+    quantization_matrix: [u8; 64]
 }
-
 pub mod dct;
 
 // fn median64<T: Ord + Copy>(values: &[T]) -> T {