opencv: Expose retinex parameters

Makes the plugin a tad more useful :)

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1845>

docs/plugins/gst_plugins_cache.json

@@ -213020,6 +213020,20 @@
                     }
                 },
                 "properties": {
+                    "gain": {
+                        "blurb": "Gain",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "128",
+                        "max": "2147483647",
+                        "min": "0",
+                        "mutable": "null",
+                        "readable": true,
+                        "type": "gint",
+                        "writable": true
+                    },
                     "method": {
                         "blurb": "Retinex method to use",
                         "conditionally-available": false,
@@ -213032,6 +213046,20 @@
                         "type": "GstRetinexMethod",
                         "writable": true
                     },
+                    "offset": {
+                        "blurb": "Offset",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "128",
+                        "max": "2147483647",
+                        "min": "0",
+                        "mutable": "null",
+                        "readable": true,
+                        "type": "gint",
+                        "writable": true
+                    },
                     "scales": {
                         "blurb": "Amount of gaussian filters (scales) used in multiscale retinex",
                         "conditionally-available": false,
@@ -213045,6 +213073,20 @@
                         "readable": true,
                         "type": "gint",
                         "writable": true
+                    },
+                    "sigma": {
+                        "blurb": "Sigma",
+                        "conditionally-available": false,
+                        "construct": false,
+                        "construct-only": false,
+                        "controllable": false,
+                        "default": "14",
+                        "max": "1.79769e+308",
+                        "min": "0",
+                        "mutable": "null",
+                        "readable": true,
+                        "type": "gdouble",
+                        "writable": true
                     }
                 },
                 "rank": "none"

ext/opencv/gstretinex.cpp

@@ -79,7 +79,10 @@ enum
 {
   PROP_0,
   PROP_METHOD,
-  PROP_SCALES
+  PROP_SCALES,
+  PROP_SIGMA,
+  PROP_GAIN,
+  PROP_OFFSET,
 };
 typedef enum
 {
@@ -89,6 +92,9 @@ typedef enum
 
 #define DEFAULT_METHOD METHOD_BASIC
 #define DEFAULT_SCALES 3
+#define DEFAULT_SIGMA 14.0
+#define DEFAULT_GAIN 128
+#define DEFAULT_OFFSET 128
 
 #define GST_TYPE_RETINEX_METHOD (gst_retinex_method_get_type ())
 static GType
@@ -160,6 +166,42 @@ gst_retinex_class_init (GstRetinexClass * klass)
           4, DEFAULT_SCALES,
           (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
 
+  /**
+   * GstRetinex:sigma:
+   *
+   * Sigma
+   *
+   * Since: 1.20
+   */
+  g_object_class_install_property (gobject_class, PROP_SIGMA,
+      g_param_spec_double ("sigma", "Sigma",
+			   "Sigma", 0.0, G_MAXDOUBLE, DEFAULT_SIGMA,
+          (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
+
+  /**
+   * GstRetinex:gain:
+   *
+   * Gain
+   *
+   * Since: 1.20
+   */
+  g_object_class_install_property (gobject_class, PROP_GAIN,
+      g_param_spec_int ("gain", "gain",
+			"Gain", 0, G_MAXINT, DEFAULT_GAIN,
+          (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
+
+  /**
+   * GstRetinex:offset:
+   *
+   * Offset
+   *
+   * Since: 1.20
+   */
+  g_object_class_install_property (gobject_class, PROP_OFFSET,
+      g_param_spec_int ("offset", "Offset",
+			"Offset", 0, G_MAXINT, DEFAULT_OFFSET,
+          (GParamFlags) (G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS)));
+
   gst_element_class_set_static_metadata (element_class,
       "Retinex image colour enhancement", "Filter/Effect/Video",
       "Multiscale retinex for colour image enhancement",
@@ -182,6 +224,9 @@ gst_retinex_init (GstRetinex * filter)
   filter->method = DEFAULT_METHOD;
   filter->scales = DEFAULT_SCALES;
   filter->current_scales = 0;
+  filter->gain = DEFAULT_GAIN;
+  filter->offset = DEFAULT_OFFSET;
+  filter->sigma = DEFAULT_SIGMA;
   gst_opencv_video_filter_set_in_place (GST_OPENCV_VIDEO_FILTER_CAST (filter),
       TRUE);
 }
@@ -217,6 +262,15 @@ gst_retinex_set_property (GObject * object, guint prop_id,
     case PROP_SCALES:
       retinex->scales = g_value_get_int (value);
       break;
+  case PROP_SIGMA:
+    retinex->sigma = g_value_get_double (value);
+    break;
+    case PROP_GAIN:
+      retinex->gain = g_value_get_int (value);
+      break;
+    case PROP_OFFSET:
+      retinex->offset = g_value_get_int (value);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -236,6 +290,15 @@ gst_retinex_get_property (GObject * object, guint prop_id,
     case PROP_SCALES:
       g_value_set_int (value, filter->scales);
       break;
+    case PROP_SIGMA:
+      g_value_set_double (value, filter->sigma);
+      break;
+    case PROP_GAIN:
+      g_value_set_int (value, filter->gain);
+      break;
+    case PROP_OFFSET:
+      g_value_set_int (value, filter->offset);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;
@@ -265,9 +328,6 @@ gst_retinex_transform_ip (GstOpencvVideoFilter * filter, GstBuffer * buf,
     Mat img)
 {
   GstRetinex *retinex = GST_RETINEX (filter);
-  double sigma = 14.0;
-  int gain = 128;
-  int offset = 128;
   int filter_size;
 
   /* Basic retinex restoration.  The image and a filtered image are converted
@@ -280,7 +340,7 @@ gst_retinex_transform_ip (GstOpencvVideoFilter * filter, GstBuffer * buf,
     log (retinex->cvA, retinex->cvB);
 
     /*  Compute log of blurred image */
-    filter_size = (int) floor (sigma * 6) / 2;
+    filter_size = (int) floor (retinex->sigma * 6) / 2;
     filter_size = filter_size * 2 + 1;
 
     img.convertTo (retinex->cvD, retinex->cvD.type ());
@@ -292,7 +352,7 @@ gst_retinex_transform_ip (GstOpencvVideoFilter * filter, GstBuffer * buf,
     subtract (retinex->cvB, retinex->cvC, retinex->cvA);
 
     /*  Restore */
-    retinex->cvA.convertTo (img, img.type (), (float) gain, (float) offset);
+    retinex->cvA.convertTo (img, img.type (), (float) retinex->gain, (float) retinex->offset);
   }
   /* Multiscale retinex restoration.  The image and a set of filtered images are
      converted to the log domain and subtracted from the original with some set
@@ -339,7 +399,7 @@ gst_retinex_transform_ip (GstOpencvVideoFilter * filter, GstBuffer * buf,
     }
 
     /*  Restore */
-    retinex->cvB.convertTo (img, img.type (), (float) gain, (float) offset);
+    retinex->cvB.convertTo (img, img.type (), (float) retinex->gain, (float) retinex->offset);
   }
 
   return GST_FLOW_OK;

ext/opencv/gstretinex.h

@@ -72,6 +72,9 @@ struct _GstRetinex
   double *weights;
   double *sigmas;
 
+  double sigma;
+  int gain, offset;
+
   cv::Mat cvA;
   cv::Mat cvB;
   cv::Mat cvC;