Detecting faces and adding santa claus hats for fun and profit

gistfile1.py

# Based on
# http://japskua.wordpress.com/2010/08/04/detecting-eyes-with-python-opencv/
# http://stackoverflow.com/questions/1650568/how-do-i-create-an-opencv-image-from-a-pil-image

import os
import sys
import logging
from cStringIO import StringIO

import cv
from PIL import Image, ImageFile

log = logging.getLogger(__name__)

RESOURCE_PATH = os.path.join(os.path.dirname(__file__), 'res')

FACE_CASCADE = cv.Load(os.path.join(RESOURCE_PATH, "model.xml")) # haarcascade_frontalface_alt_tree.xml
MUETZE = Image.open(StringIO(file(os.path.join(RESOURCE_PATH, "muetze.png"), "rb").read()))

def add_muetze(pil_image):
    rgb = pil_image.convert("RGB")
    image = cv.CreateImageHeader(rgb.size, cv.IPL_DEPTH_8U, 3)
    cv.SetData(image, rgb.rotate(180).tostring()[::-1])

    min_size = (20,20)
    image_scale = 2
    haar_scale = 1.1
    min_neighbors = 7
    haar_flags = 0

    # Allocate the temporary images
    gray = cv.CreateImage((image.width, image.height), 8, 1)
    smallImage = cv.CreateImage((cv.Round(image.width / image_scale), cv.Round(image.height / image_scale)), 8 ,1)

    # Convert color input image to grayscale
    cv.CvtColor(image, gray, cv.CV_RGB2GRAY)

    # Scale input image for faster processing
    cv.Resize(gray, smallImage, cv.CV_INTER_LINEAR)

    # Equalize the histogram
    cv.EqualizeHist(smallImage, smallImage)

    faces = cv.HaarDetectObjects(smallImage, FACE_CASCADE,
        cv.CreateMemStorage(0), haar_scale,
        min_neighbors, haar_flags, min_size)

    for ((x, y, w, h), n) in faces:
        x = int(x * image_scale)
        y = int(y * image_scale)
        w = int(w * image_scale)
        h = int(h * image_scale)

        x = int(x - w/2)
        w = int(w * 1.6)
        h = int(h * 1.6)

        scaled_muetze = MUETZE.copy()
        scaled_muetze.thumbnail((w, h), Image.ADAPTIVE)

        box = (x, y - int(h*0.5))
        pil_image.paste(scaled_muetze, box, scaled_muetze)
    return pil_image

if __name__ == "__main__":
    image = Image.open(StringIO(file(sys.argv[1]).read()))
    image.load()
    image = add_muetze(image)
    image.show()