Add median filter

dlib/image/filters/median.d

@@ -0,0 +1,96 @@
+/*
+Copyright (c) 2022-2023 Oleg Baharev, Timur Gafarov
+
+Boost Software License - Version 1.0 - August 17th, 2003
+
+Permission is hereby granted, free of charge, to any person or organization
+obtaining a copy of the software and accompanying documentation covered by
+this license (the "Software") to use, reproduce, display, distribute,
+execute, and transmit the Software, and to prepare derivative works of the
+Software, and to permit third-parties to whom the Software is furnished to
+do so, all subject to the following:
+
+The copyright notices in the Software and this entire statement, including
+the above license grant, this restriction and the following disclaimer,
+must be included in all copies of the Software, in whole or in part, and
+all derivative works of the Software, unless such copies or derivative
+works are solely in the form of machine-executable object code generated by
+a source language processor.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+*/
+
+/**
+ * Median filter.
+ *
+ * Copyright: Oleg Baharev, Timur Gafarov 2022-2023.
+ * License: $(LINK2 boost.org/LICENSE_1_0.txt, Boost License 1.0).
+ * Authors: Oleg Baharev, Timur Gafarov
+ */
+module dlib.image.filters.median;
+
+import std.algorithm: sort;
+import dlib.core.memory;
+import dlib.image.image;
+import dlib.image.color;
+
+/// Median filter
+auto medianFilter(SuperImage img, SuperImage outp, uint windowWidth, uint windowHeight)
+{
+    SuperImage res;
+    if (outp)
+        res = outp;
+    else
+        res = img.dup;
+
+    struct ColorAndLuma
+    {
+        Color4f color;
+        float luminance;
+    }
+
+    ColorAndLuma[] window = New!(ColorAndLuma[])(windowWidth * windowHeight);
+
+    uint halfWindowWidth = windowWidth / 2;
+    uint halfWindowHeight = windowHeight / 2;
+
+    foreach(y; 0..img.height)
+    foreach(x; 0..img.width)
+    {
+        foreach(wy; 0..windowHeight)
+        foreach(wx; 0..windowWidth)
+        {
+            int sampleX = x - halfWindowWidth + wx;
+            int sampleY = y - halfWindowHeight + wy;
+            if (sampleX < 0) sampleX = 0;
+            else if (sampleX >= img.width) sampleX = img.width - 1;
+            if (sampleY < 0) sampleY = 0;
+            else if (sampleY >= img.height) sampleY = img.height - 1;
+
+            auto sample = img[sampleX, sampleY];
+
+            auto windowSample = &window[wy * windowWidth + wx];
+            windowSample.color = sample;
+            windowSample.luminance = sample.luminance;
+        }
+
+        sort!("a.luminance > b.luminance")(window);
+        res[x, y] = window[$ / 2].color;
+    }
+
+    Delete(window);
+
+    return res;
+}
+
+/// ditto
+SuperImage medianFilter(SuperImage img, uint windowWidth, uint windowHeight)
+{
+    return medianFilter(img, null, windowWidth, windowHeight);
+}

dlib/image/filters/package.d

@@ -43,6 +43,7 @@ public
     import dlib.image.filters.desaturate;
     import dlib.image.filters.edgedetect;
     import dlib.image.filters.lens;
+    import dlib.image.filters.median;
     import dlib.image.filters.morphology;
     import dlib.image.filters.normalmap;
     import dlib.image.filters.sharpen;