Added parameter to control high-contrast detection sensitivity

config/openalpr.conf.in

@@ -49,6 +49,10 @@ must_match_pattern = 0
 ; Bypasses plate detection.  If this is set to 1, the library assumes that each region provided is a likely plate area.
 skip_detection = 0
 
+; OpenALPR detects high-contrast plate crops and uses an alternative edge detection technique.  Setting this to 0.0 
+; would classify  ALL images as high-contrast, setting it to 1.0 would classify no images as high-contrast. 
+contrast_detection_threshold = 0.3
+
 max_plate_angle_degrees = 15
 
 ocr_min_font_point = 6

src/openalpr/config.cpp

@@ -183,6 +183,8 @@ namespace alpr
     maxDetectionInputWidth = getInt(ini, "", "max_detection_input_width", 1280);
     maxDetectionInputHeight = getInt(ini, "", "max_detection_input_height", 768);
 
+    contrastDetectionThreshold = getFloat(ini, "", "contrast_detection_threshold", 0.3);
+    
     mustMatchPattern = getBoolean(ini, "", "must_match_pattern", false);
     
     skipDetection = getBoolean(ini, "", "skip_detection", false);

src/openalpr/config.h

@@ -57,6 +57,8 @@ namespace alpr
       int maxDetectionInputWidth;
       int maxDetectionInputHeight;
       
+      float contrastDetectionThreshold;
+      
       bool skipDetection;
 
       bool auto_invert;

src/openalpr/edges/edgefinder.cpp

@@ -339,7 +339,7 @@ namespace alpr
       cout << "High Contrast Detection Time: " << diffclock(startTime, endTime) << "ms." << endl;
     }
     
-    return contrast > 0.3;
+    return contrast > pipeline_data->config->contrastDetectionThreshold;
   }
 
 }