This is a very old article I wrote on my last blog I hope to write another, more up-to-date one soon.

I hacked together this basic script to detect faces in images using OpenCV, Python, and ImageMagick. It’s a fun wee learning experience.

At the moment it tries to replace a face with an image. Some more tweaking, and it should be good to go.

I also suppose it’s not much of a tutorial, but if you understand Python, and you have managed to get OpenCV installed, you should be fine.

To run it:

  import web, sys, os, subprocess, uuid
  from import *
  from opencv.highgui import *
  from shutil import copy
  def detectObjects(image, imagefile):
    grayscale = cvCreateImage(cvSize(image.width, image.height), 8, 1)
    cvCvtColor(image, grayscale, CV_BGR2GRAY)
    storage = cvCreateMemStorage(0)
    cvEqualizeHist(grayscale, grayscale)
    cascade = cvLoadHaarClassifierCascade(
    faces = cvHaarDetectObjects(grayscale, cascade, storage, 1.2, 2,
                              CV_HAAR_DO_CANNY_PRUNING, cvSize(50,50))
    if > 0:
      for f in faces:
          print("found a face: [(%d,%d) -> (%d,%d)]" % (f.x, f.y, f.x+f.width, f.y+f.height))
          foundFace(imagefile, f)
  def foundFace(imagefile, f):
      #os.system("convert {image} -stroke red -fill red -draw \"rectangle {a},{b} {c},{d}\" {output}".format(
      os.system("convert {image} -draw \"image SrcOver {a},{b} {c},{d} biglazer.png\" {output}".format(
  urls = (
      '/upload', 'Upload',
  class Upload:
      def GET(self):
          web.header("Content-Type","text/html; charset=utf-8")
          return """<html><head><link rel="shortcut icon" href="/static/favicon.ico"
                    <form method="POST" enctype="multipart/form-data" action="">
                    <input type="file" name="myfile" />
                    <input type="submit" />
      def POST(self):
          x = web.input(myfile={})
          filedir = '/home/mike/python/uploads' # change this to the directory you want to store the file in.
          if 'myfile' in x: # to check if the file-object is created
              filepath=x.myfile.filename.replace('\\','/') # replaces the windows-style slashes with linux ones.
              #filename=filepath.split('/')[-1] # splits the and chooses the last part (the filename with extension)
              filename = str(uuid.uuid4())
              fout = open(filedir +'/'+ filename,'w') # creates the file where the uploaded file should be stored
              fout.write( # writes the uploaded file to the newly created file.
              fout.close() # closes the file, upload complete.
              # detect face
              imagefile = filedir +'/'+ filename;
              image = cvLoadImage(imagefile);
              unique_name = str(uuid.uuid4())
              output_path = '/home/mike/python/static/%s.png' % unique_name
              if (detectObjects(image, imagefile) > 0):
                  copy(imagefile, output_path)
                  web.redirect("static/%s.png" % unique_name)
                  return """No face found."""
          raise web.seeother('/upload')
  if __name__ == "__main__":
    app = web.application(urls, globals(), True)

There are quite a few things you’ll need to change to get it working as well, such as the paths etc.

There are some problems – it doesn’t like bitmap (*.BMP) nor cartoon type images. Here are some examples of images that worked:

John Key

John Key Derp