1. How to make IF statement for im.MergeThreshold use in Viola-Jones Algorithm

Hi, i am trying to code an algorithm to detect facial features and extract its values.

I am using viola-jones algorithm for mouth, nose, and eyes detection. In the code, theres a threshold that is used to determine the number of detected object in the image. My problem is, when i input a new image, the algorithm cannot detect the features. Only when i change the threshold value will it detect. The values i specifies are random and are by trial and error. Are there a way for using an if or switch case statement for it to automatically try other threshold value? I am using a normalized 100x100 grayscale images of already cropped out face from original image to detect the eyes, nose, mouth.

example code:

mouthdetect = vision.CascadeObjectDetector('Mouth');
% Threshold value //CHANGE HERE IF ROI IS NOT DETECTED
mouthdetect.MergeThreshold = 50;
% Detects mouth in image.
bb_m = step(mouthdetect, face);
% Annotation
an_m = insertObjectAnnotation(face, 'rectangle', bb_m, 'Mouth');
% Crop segmented mouth
mouth = imcrop(face, bb_m);

2. Also, does anyone know what should i extract from gabor filtered image for expression recognition? I've read some research that uses std, var, pca, dct. But i get an array of values not a single value.

Answer 1

[Florian Morsch]

You can check your variables if they have values in them. If not, change the threshold and run again.

1. Create a flag, like "FaceFound = 0"

2. Use a while:

mouthdetect = vision.CascadeObjectDetector('Mouth');

mouthdetect.MergeThreshold = 1; % Threshold value, starts at 1 or any value you want

FaceFound = 0;

while FaceFound = 0

      bb_m = step(mouthdetect, face); % Detects mouth in image.

      if(bb_m == []) % Check if a mouth is found, if not increase the Threshold by 1
          mouthdetect.MergeThreshold = mouthdetect.MergeThreshold + 1;
      else  
          an_m = insertObjectAnnotation(face, 'rectangle', bb_m, 'Mouth'); % Annotation

          mouth = imcrop(face, bb_m); % Crop segmented mouth

          FaceFound = 1;
      end
 end

This way your programm will run as long as there is nothing found and increase the threshold. After a mouth is found the loop ends.

Remember to reset the variables before you run the loop again, if you still have values in your workspace you might get wrong results.

[Amirul Ibrahim]

Thanks a lot. This works for one of my application using it.

[amina benameur]

I am a graduate student at the University of Science and Technology Mohamed Boudiaf in Oran in Algeria and I am doing research in the theme Analysis of shape and texture of facial regions for the recognition of expressions.

i need a viola jones algorithm