detect the number of faces on image and prompt error message if there is more than 1 face

Hi all,

i am doing a face detection and recognition system . I am currently using matlab R2013a with computer vision tootkit. my concern now is that i would like to allow my user to upload a image from their computer directory but in order to do so, the image must only contain 1 front face. To prevent user from uploading more than 1 face, i would like to prompt them an error message. but i am not sure how to go about it.

appreciate anyone of your help is solving the question.

[filename, pathname] = uigetfile({'*.jpg;*.png;*.gif;*.bmp', 'All Image Files (*.jpg, *.png, *.gif, *.bmp)'; ...
      '*.*',                   'All Files (*.*)'}, ...
    'Pick an image file');

if filename ~= 0
FileName = fullfile(pathname,filename);
end

axes (handles.axes1);
F = imread (FileName);
imshow(F, 'Parent', handles.axes1);
faceDetector=vision.CascadeObjectDetector;
faceDetector.MinSize=[20 20];
faceDetector.MergeThreshold = 20;
bbox = step(faceDetector,F);
axes (handles.axes1);
imshow(F);
if numel(bbox) == 0
    errordlg('No face is detected in image. Please upload another one.');
end
hold on;
for i = 1:size(bbox,1)
    rectangle('Position',bbox(i,:),'LineWidth',3,'LineStyle','-','EdgeColor','r');
end    
hold off;

Answer 1

[Dima Lisin]

bbox is an M-by-4 matrix, where is row represents a bounding box as [x, y, width, height]. So if size(bbox, 1) is 0, then no faces were detected. If size(bbox, 1) is 1, then one face was detected. If it is greater than 1, then multiple faces were detected.

[Eliza Tham]

Hi Dima, when i enter the code below, they happen to have some errors,

When i insert and image of more than 1 person, instead of giving me the error message 'Please upload another one' it prompts a message of 'Image unsuitable for enrolment. Please upload another one.'

When I enter the image without any face, it prompts me with ''Image unsuitable enrolment. Please upload another one.' which appears to be right.

Is there anything wrong with the codes, i type?

if  size(bbox, 1) == 0
    errordlg('Image unsuitable enrolment. Please upload another one.');
elseif   size(bbox, 1)>1
    errordlg('Please upload another one.');
else 
    msgbox('One Face detected, Image suitable to upload');

[Dima Lisin]

Look at bbox in the debugger. Draw the bounding boxes on the image. There is always the possibility that vision.CascadeObjectDetector simply did not detect all the faces.