Face Detection with the Raspberry Pi Camera Board

I have a very basic face detection routine running with the Raspberry Pi camera board.

To do this I used Robidouille’s library functions (see previous post). I then modified the raspicam_cv.c example to use the face detection routine from Learning OpenCV. There were some tweaks so I will post the code below. You also need to modify the makefile to include the OpenCV object detection libraries.


Modified from code supplied by Emil Valkov (Raspicam libraries) and Noah Kuntz (Face detection)

License: http://www.opensource.org/licenses/bsd-license.php


#include <cv.h>
#include <highgui.h>

#include "RaspiCamCV.h"

int main(int argc, const char** argv){

//Initialise Camera object
 RaspiCamCvCapture * capture = raspiCamCvCreateCameraCapture(0); // Index doesn't really matter

 //initialise memory storage for Haar objects
 CvMemStorage* storage = cvCreateMemStorage(0);

 //Set up Haar Cascade - need quoted file in directory of program
 CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad( "haarcascade_frontalface_alt2.xml", 0, 0, 0);

 //Set scale down factor
 double scale = 1.8;

//Set colours for multiple faces
 static CvScalar colors[] = { {{0,0,255}}, {{0,128,255}}, {{0,255,255}}, {{0,255,0}}, {{255,128,0}}, {{255,255,0}}, {{255,0,0}}, {{255,0,255}} };

 //Open Window for Viewing
 cvNamedWindow("RaspiCamTest", 1);

 //Loop for frames - while no keypress
 do {
 //Capture a frame
 IplImage* img = raspiCamCvQueryFrame(capture);

 //Clear memory object
 cvClearMemStorage( storage );

 //Initialise grayscale image
 IplImage* gray = cvCreateImage( cvSize(img->width,img->height), 8, 1 );

 //Shrink image
 IplImage* small_img = cvCreateImage(cvSize( cvRound(img->width/scale), cvRound(img->height/scale)), 8, 1 );

 //Convert to gray
 cvCvtColor( img, gray, CV_BGR2GRAY );

 //Resize to small image size
 cvResize( gray, small_img, CV_INTER_LINEAR );

 //Finished with gray image - release memory
 cvReleaseImage( &gray );

 //Vertical flip image as camera is upside down
 cvFlip(small_img, NULL, -1);

 cvEqualizeHist( small_img, small_img );

 // Detect objects - last arg is max size -test parameters to optimise
 //Will detect biggest face with 6th arg as 4
 CvSeq* objects = cvHaarDetectObjects( small_img, cascade, storage, 1.1, 4, 4, cvSize( 40, 50 ), cvSize(small_img->width, small_img->height));

 int i;
 for(i = 0; i < (objects ? objects->total : 0); i++ )
 CvRect* r = (CvRect*)cvGetSeqElem( objects, i );

 //My compiler doesnt seem to be able to cope with default variables - need to specify all args - need to change '.' to '->' as r is pointer

 //This line appears to be the problem
 cvRectangle(small_img, cvPoint(r->x,r->y), cvPoint(r->x+r->width,r->y+r->height), colors[i%8], 2, 8, 0);

 cvShowImage("RaspiCamTest", small_img);
 //cvReleaseImage( &gray );
 cvReleaseImage( &small_img );

 } while (cvWaitKey(10) < 0);

 //Close window

 //Release memory

 return 0;



OBJS = objs

CFLAGS_OPENCV = -I/usr/include/opencv
LDFLAGS2_OPENCV = -lopencv_highgui -lopencv_core -lopencv_legacy -lopencv_video -lopencv_features2d -lopencv_calib3d -lopencv_imgproc -lopencv_objdetect

USERLAND_ROOT = $(HOME)/git/raspberrypi/userland
 -I$(USERLAND_ROOT)/host_applications/linux/libs/bcm_host/include \
 -I$(USERLAND_ROOT)/host_applications/linux/apps/raspicam \
 -I$(USERLAND_ROOT)/interface/vcos/pthreads \
 -I$(USERLAND_ROOT)/interface/vmcs_host/linux \
 -I$(USERLAND_ROOT)/interface/mmal \

LDFLAGS_PI = -L$(USERLAND_ROOT)/build/lib -lmmal_core -lmmal -l mmal_util -lvcos -lbcm_host



ifeq ($(BUILD_TYPE), debug)
ifeq ($(BUILD_TYPE), release)

LDFLAGS2 = $(LDFLAGS2_OPENCV) $(LDFLAGS_PI) -lX11 -lXext -lrt -lstdc++

 $(OBJS)/RaspiCamControl.o \
 $(OBJS)/RaspiCLI.o \
 $(OBJS)/RaspiCamCV.o \

 $(OBJS)/RaspiCamTest.o \

TARGETS = libraspicamcv.a raspicamtest

all: $(TARGETS)

$(OBJS)/%.o: %.c
 gcc -c $(CFLAGS) $< -o $@

$(OBJS)/%.o: $(USERLAND_ROOT)/host_applications/linux/apps/raspicam/%.c
 gcc -c $(CFLAGS) $< -o $@

libraspicamcv.a: $(RASPICAMCV_OBJS)
 ar rcs libraspicamcv.a -o $+

raspicamtest: $(RASPICAMTEST_OBJS) libraspicamcv.a
 gcc $(LDFLAGS) $+ $(LDFLAGS2) -L. -lraspicamcv -o $@

 rm -f $(OBJS)/* $(TARGETS)

-include $(OBJS)/*.d

Hacker News Update: Raspicam & WeMo

A quick update on my recent discoveries.


I now have a Raspberry Pi Camera Board (Raspicam)!

There is a brilliant combo deal on at the moment allowing you to buy a Raspicam, Model A + 4GB SD card for about £35 (including VAT + shipping!)! That’s £35 for a device that can run OpenCV with a camera capable of 30fps at HD resolutions. I will leave you to think about that for a moment.

The downside is that the software is still not quite there. The Raspicam couples directly to the Raspberry Pi; this means it is not (at the moment) available as a standard USB video device (e.g. /dev/video0 on Linux). Now most Linux software and packages like SimpleCV work based on a standard USB video device. This means as of 24 October 2013 you cannot use SimpleCV with the Raspicam.

However, not to fret! The Internet is on it. I imagine that we will see better drivers for the Raspicam from the official development communities very soon. While we wait:

WeMo and Python

As you will see from the previous posts I have been using IFTTT as a make-shift interface between my Raspberry Pi and my WeMo Motion detector and switch.  This morning though I found a Python module that appears to enable you to control the Switch and listen to motion events via Python. Hurray!

The module is called ouimeaux (there is a French theme this week). Details can be found here: link.

Very soon I hope to adapt my existing code to control my Hue lights based on motion events (e.g. turn on when someone walks in the room, turn off when no motion). Watch this space.