Added random_color_transform and disturb_colors().

dlib/image_transforms.h

@@ -24,6 +24,7 @@
 #include "image_transforms/interpolation.h"
 #include "image_transforms/fhog.h"
 #include "image_transforms/lbp.h"
+#include "image_transforms/random_color_transform.h"
 
 #endif // DLIB_IMAGE_TRANSFORMs_
 

dlib/image_transforms/random_color_transform.h

+// Copyright (C) 2016  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_RANDOM_cOLOR_TRANSFORM_Hh_
+#define DLIB_RANDOM_cOLOR_TRANSFORM_Hh_
+
+#include "random_color_transform_abstract.h"
+#include "../image_processing/generic_image.h"
+#include "../pixel.h"
+#include "../rand.h"
+
+namespace dlib
+{
+
+// ----------------------------------------------------------------------------------------
+
+    class random_color_transform
+    {
+    public:
+
+        random_color_transform (
+            dlib::rand& rnd,
+            const double gamma_magnitude = 0.5,
+            const double color_magnitude = 0.2
+        )
+        {
+            // pick a random gamma correction factor.  
+            double gamma = std::max(0.0, 1 + gamma_magnitude*(rnd.get_random_double()-0.5));
+
+            // pick a random color balancing scheme.
+            double red_scale = 1-rnd.get_random_double()*color_magnitude;
+            double green_scale = 1-rnd.get_random_double()*color_magnitude;
+            double blue_scale = 1-rnd.get_random_double()*color_magnitude;
+            const double m = 255*std::max(std::max(red_scale,green_scale),blue_scale);
+            red_scale /= m;
+            green_scale /= m;
+            blue_scale /= m;
+
+            // Now compute a lookup table for all the color channels.  The table tells us
+            // what the transform does.
+            table.resize(256*3);
+            unsigned long i = 0;
+            for (int k = 0; k < 256; ++k)
+            {
+                double v = 255*std::pow(k*red_scale, gamma);
+                table[i++] = (unsigned char)(v + 0.5);
+            }
+            for (int k = 0; k < 256; ++k)
+            {
+                double v = 255*std::pow(k*green_scale, gamma);
+                table[i++] = (unsigned char)(v + 0.5);
+            }
+            for (int k = 0; k < 256; ++k)
+            {
+                double v = 255*std::pow(k*blue_scale, gamma);
+                table[i++] = (unsigned char)(v + 0.5);
+            }
+        }
+
+        rgb_pixel operator()(rgb_pixel p) const
+        {
+            p.red = table[(unsigned int)p.red];
+            p.green = table[(unsigned int)p.green+256];
+            p.blue = table[(unsigned int)p.blue+512];
+            return p;
+        }
+
+    private:
+        std::vector<unsigned char> table;
+    };
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    void disturb_colors (
+        image_type& img_,
+        dlib::rand& rnd,
+        const double gamma_magnitude = 0.5,
+        const double color_magnitude = 0.2
+    )
+    {
+        image_view<image_type> img(img_);
+        random_color_transform tform(rnd, gamma_magnitude, color_magnitude);
+        for (long r = 0; r < img.nr(); ++r)
+        {
+            for (long c = 0; c < img.nc(); ++c)
+            {
+                rgb_pixel temp;
+                assign_pixel(temp, img[r][c]);
+                temp = tform(temp);
+                assign_pixel(img[r][c], temp);
+            }
+        }
+    }
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_RANDOM_cOLOR_TRANSFORM_Hh_
+

dlib/image_transforms/random_color_transform_abstract.h

+// Copyright (C) 2016  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#undef DLIB_RANDOM_cOLOR_TRANSFORM_ABSTRACT_Hh_
+#ifdef DLIB_RANDOM_cOLOR_TRANSFORM_ABSTRACT_Hh_
+
+#include "../image_processing/generic_image.h"
+#include "../pixel.h"
+#include "../rand.h"
+
+namespace dlib
+{
+
+// ----------------------------------------------------------------------------------------
+
+    class random_color_transform
+    {
+        /*!
+            WHAT THIS OBJECT REPRESENTS
+                This object generates a random color balancing and gamma correction
+                transform.  It then allows you to apply that specific transform to as many
+                rgb_pixel objects as you like.
+        !*/
+
+    public:
+
+        random_color_transform (
+            dlib::rand& rnd,
+            const double gamma_magnitude = 0.5,
+            const double color_magnitude = 0.2
+        );
+        /*!
+            requires
+                - 0 <= gamma_magnitude 
+                - 0 <= color_magnitude <= 1
+            ensures
+                - This constructor generates a random color transform which can be applied
+                  by calling this object's operator() method.
+                - The color transform is a gamma correction and color rebalancing.  If
+                  gamma_magnitude == 0 and color_magnitude == 0 then the transform doesn't
+                  change any colors at all.  However, the larger these parameters the more
+                  noticeable the resulting transform.
+        !*/
+
+        rgb_pixel operator()(
+            rgb_pixel p
+        ) const;
+        /*!
+            ensures
+                - returns the color transformed version of p. 
+        !*/
+    };
+
+// ----------------------------------------------------------------------------------------
+
+    template <typename image_type>
+    void disturb_colors (
+        image_type& img,
+        dlib::rand& rnd,
+        const double gamma_magnitude = 0.5,
+        const double color_magnitude = 0.2
+    );
+    /*!
+        requires
+            - image_type == an image object that implements the interface defined in
+              dlib/image_processing/generic_image.h 
+        ensures
+            - Applies a random color transform to the given image.  This is done by
+              creating a random_color_transform with the given parameters and then
+              transforming each pixel in the image with the resulting transform.
+    !*/
+
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_RANDOM_cOLOR_TRANSFORM_ABSTRACT_Hh_
+