Add DifferenceHash implemnentations

src/lib.rs

@@ -17,6 +17,7 @@
 //! ## Supported Algorithms
 //!
 //! - Average Hash (aHash)
+//! - Difference Hash (dHash)
 //!
 //! ## Usage
 //!
@@ -88,6 +89,60 @@ pub fn average_hash(image: &image::DynamicImage, op: &ImageOp) -> Vec<bool> {
  pixels.iter().map(|&v| v as u16 > average).collect()
 }
 
+/// Provides difference hash (dHash) calculation.
+pub struct DifferenceHash<'a> {
+ op: &'a ImageOp,
+}
+
+impl<'a> DifferenceHash<'a> {
+ /// Creates a new `DifferenceHasher` with default parameters.
+ pub fn new() -> Self {
+ DifferenceHash::default()
+ }
+
+ /// Creates a new `DifferenceHasher` with the specified parameters.
+ pub fn with_op(op: &'a ImageOp) -> Self {
+ DifferenceHash { op }
+ }
+
+ /// Calculates difference hash (dHash) of the image and returns as a hex string.
+ pub fn hash(&self, image: &image::DynamicImage) -> String {
+ let bits = difference_hash(image, self.op);
+ let bytes = bits_to_bytes(&bits);
+ bytes_to_hex(&bytes)
+ }
+}
+
+impl Default for DifferenceHash<'_> {
+ /// Creates a new `DifferenceHasher` with default parameters.
+ fn default() -> Self {
+ DifferenceHash {
+ op: &ImageOp {
+ width: 9,
+ height: 8,
+ filter: FilterType::Lanczos3,
+ },
+ }
+ }
+}
+
+/// Calculates difference hash (dHash) of the image.
+pub fn difference_hash(image: &image::DynamicImage, op: &ImageOp) -> Vec<bool> {
+ let preprocessed = image
+ .grayscale()
+ .resize_exact(op.width as u32, op.height as u32, op.filter);
+ let pixels = preprocessed.into_luma8().into_raw();
+ let mut bits = vec![false; ((op.width - 1) * op.height) as usize];
+ for y in 0..op.height {
+ for x in 0..op.width - 1 {
+ let offset_p = (y * op.width + x) as usize;
+ let offset_b = (y * (op.width - 1) + x) as usize;
+ bits[offset_b] = pixels[offset_p + 1] > pixels[offset_p];
+ }
+ }
+ bits
+}
+
 fn bits_to_bytes(bits: &[bool]) -> Vec<u8> {
  let mut bytes = vec![0; (bits.len() + 7) / 8];
  for (i, bit) in bits.iter().enumerate() {

tests/test.rs

@@ -27,3 +27,17 @@ fn test_average_hash_2() {
  let result = AverageHash::default().hash(&dynimg);
  assert_eq!(result, "fff7e7e3c3000000");
 }
+
+#[test]
+fn test_difference_hash_1() {
+ let dynimg = image::open("tests/1.jpg").unwrap();
+ let result = DifferenceHash::default().hash(&dynimg);
+ assert_eq!(result, "e0e0f0c4c6d290c0");
+}
+
+#[test]
+fn test_difference_hash_2() {
+ let dynimg = image::open("tests/2.jpg").unwrap();
+ let result = DifferenceHash::default().hash(&dynimg);
+ assert_eq!(result, "ededcc860b0c19b6");
+}