Add support for 'Magic Kernel Sharp' resize algorithms

crates/bindings/chainner_ext.pyi

@@ -80,6 +80,8 @@ class ResizeFilter(Enum):
     Lanczos = 4
     Lagrange = 7
     Gauss = 5
+    MKS2013 = 12
+    MKS2021 = 13
 
 def resize(
     img: np.ndarray,

crates/bindings/src/resize.rs

@@ -24,6 +24,8 @@ pub enum ResizeFilter {
     Lanczos = 4,
     Lagrange = 7,
     Gauss = 5,
+    MKS2013 = 12,
+    MKS2021 = 13,
 }
 
 impl From<ResizeFilter> for Filter {
@@ -41,6 +43,8 @@ impl From<ResizeFilter> for Filter {
             ResizeFilter::Lanczos => Filter::Lanczos3,
             ResizeFilter::Lagrange => Filter::Lagrange,
             ResizeFilter::Gauss => Filter::Gauss,
+            ResizeFilter::MKS2013 => Filter::MKS2013,
+            ResizeFilter::MKS2021 => Filter::MKS2021,
         }
     }
 }

crates/image-ops/src/scale/filter.rs

@@ -12,6 +12,8 @@ pub enum Filter {
     Lanczos3,
     Lagrange,
     Gauss,
+    MKS2013,
+    MKS2021,
 }
 
 #[inline]
@@ -65,6 +67,40 @@ fn lagrange(x: f32, support: f32) -> f32 {
     value
 }
 
+// Taken from
+// https://github.com/ImageMagick/ImageMagick/blob/b5f748c38ad5bb6b58f46411b1bcb78392b5f575/MagickCore/resize.c#L428
+fn mks2013(x: f32) -> f32 {
+    let x = x.abs();
+    if x < 0.5 {
+        0.625 + 1.75 * (0.5 - x) * (0.5 + x)
+    } else if x < 1.5 {
+        (1.0 - x) * (1.75 - x)
+    } else if x < 2.5 {
+        -0.125 * (2.5 - x) * (2.5 - x)
+    } else {
+        0.0
+    }
+}
+
+// Taken from
+// https://github.com/ImageMagick/ImageMagick/blob/b5f748c38ad5bb6b58f46411b1bcb78392b5f575/MagickCore/resize.c#L448
+fn mks2021(x: f32) -> f32 {
+    let x = x.abs();
+    if x < 0.5 {
+        577.0 / 576.0 - 239.0 / 144.0 * x * x
+    } else if x < 1.5 {
+        35.0 / 36.0 * (x - 1.0) * (x - 239.0 / 140.0)
+    } else if x < 2.5 {
+        1.0 / 6.0 * (x - 2.0) * (65.0 / 24.0 - x)
+    } else if x < 3.5 {
+        1.0 / 36.0 * (x - 3.0) * (x - 3.75)
+    } else if x < 4.5 {
+        -1.0 / 288.0 * (x - 4.5) * (x - 4.5)
+    } else {
+        0.0
+    }
+}
+
 impl From<Filter> for resize::Type {
     fn from(filter: Filter) -> Self {
         match filter {
@@ -108,6 +144,14 @@ impl From<Filter> for resize::Type {
                 resize::Type::Custom(filter)
             }
             Filter::Gauss => resize::Type::Gaussian,
-        }
+            Filter::MKS2013 => {
+                let filter = resize::Filter::new(Box::new(|x| mks2013(x)), 2.5);
+                resize::Type::Custom(filter)
+            }
+            Filter::MKS2021 => {
+                let filter = resize::Filter::new(Box::new(|x| mks2021(x)), 4.5);
+                resize::Type::Custom(filter)
+            }
+		}
     }
 }

crates/image-ops/src/scale/scale.rs

@@ -293,4 +293,34 @@ mod tests {
         let nn = super::scale(original.view(), new_size, filter).unwrap();
         nn.snapshot("resize_lagrange_200");
     }
+
+    #[test]
+    fn scale_mks2013() {
+        let filter = super::Filter::MKS2013;
+
+        let original = small_portrait();
+        let new_size = original.size().scale(4.);
+        let nn = super::scale(original.view(), new_size, filter).unwrap();
+        nn.snapshot("resize_mks2013_4x");
+
+        let original = read_portrait();
+        let new_size = Size::new(200, 200);
+        let nn = super::scale(original.view(), new_size, filter).unwrap();
+        nn.snapshot("resize_mks2013_200");
+    }
+
+    #[test]
+    fn scale_mks2021() {
+        let filter = super::Filter::MKS2021;
+
+        let original = small_portrait();
+        let new_size = original.size().scale(4.);
+        let nn = super::scale(original.view(), new_size, filter).unwrap();
+        nn.snapshot("resize_mks2021_4x");
+
+        let original = read_portrait();
+        let new_size = Size::new(200, 200);
+        let nn = super::scale(original.view(), new_size, filter).unwrap();
+        nn.snapshot("resize_mks2021_200");
+    }
 }