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Month: December 2009

OpenCV: Hue, Saturation and Value.

Here a simple OpenCV example of separation of a image into its hue, saturation and value channels.

#include 
#include 
#include 

int main( int argc, char **argv ){
    IplImage *img, *hsv, *hue, *sat, *val;
    int key = 0, depth;
    CvSize size;

    /* Load command line passed image, check it. */
    if (argc>1) {
        img = cvLoadImage(argv[1], CV_LOAD_IMAGE_COLOR);
        if(!img){
            printf("Could not open image.");
            exit -1;
        }
        if(img->nChannels!=3){
            printf("We need color image!");
            exit -1;
        }
    } else {
        printf("Usage: %s VIDEO_FILE\n", argv[0]);
        return 1;
    }

    /* Create a hsv image with 3 channels and hue, sat e val with 1 channel.
       All with the same size */
    size = cvGetSize(img);
    depth = img->depth;
    hue = cvCreateImage(size, depth, 1);
    sat = cvCreateImage(size, depth, 1);
    val = cvCreateImage(size, depth, 1);
    hsv = cvCreateImage(size, depth, 3);
    cvZero(hue);
    cvZero(sat);
    cvZero(val);
    cvZero(hsv);

    /* Convert from Red-Green-Blue to Hue-Saturation-Value */
    cvCvtColor( img, hsv, CV_BGR2HSV );

    /* Split hue, saturation and value of hsv on them */
    cvSplit(hsv, hue, sat, val, 0);
    
    /* Create windows, display them, wait for a key */
    cvNamedWindow("original", CV_WINDOW_AUTOSIZE);
    cvNamedWindow("hue", CV_WINDOW_AUTOSIZE);
    cvNamedWindow("saturation", CV_WINDOW_AUTOSIZE);
    cvNamedWindow("value", CV_WINDOW_AUTOSIZE);

    cvShowImage("original", img);
    cvShowImage("hue", hue);
    cvShowImage("saturation", sat);
    cvShowImage("value", val);

    cvWaitKey(0);

    /* Free memory and get out */
    cvDestroyWindow("original");
    cvDestroyWindow("hue");
    cvDestroyWindow("saturation");
    cvDestroyWindow("value");

    cvReleaseImage(&img);
    cvReleaseImage(&hsv);
    cvReleaseImage(&hue);
    cvReleaseImage(&sat);
    cvReleaseImage(&val);

    return 0;
}

Resized original image, photo by Robert Bradshaw at Wikimedia Commons.

Sunset Peter Iredale

Hue channel:

hue sunset Peter Iredale

Saturation channel:

saturation sunset Peter Iredale

Value channel:

value sunset Peter Iredale

OpenCV: adding two images

This is a very simple example of how to open two images and display them added.

I got two pictures at project Commons from Wikimedia that were highlighted on Featured Pictures. I did a crop on both to have the same size, as I’m trying to make this example as simple as possible.

The first one is a photo of our Milky Way, taken at Paranal Observatory by Stéphane Guisard.

milkyway

The second one is a California surfer inside wave, taken by Mila Zinkova.

surfer

In this simple OpenCV code below, we open the images, create a new one to display the result and use cvAdd to add them. We do not save the result or handle more than the ordinary case of two images with the same size.

#include 
#include 
#include 

int main( int argc, char **argv ){
    IplImage *surfer, *milkyway, *result;
    int key = 0;
    CvSize size;

    /* load images, check, get size (both should have the same) */
    surfer = cvLoadImage("surfer.jpg", CV_LOAD_IMAGE_COLOR);
    milkyway = cvLoadImage("milkyway.jpg", CV_LOAD_IMAGE_COLOR);
    if((!surfer)||(!milkyway)){
        printf("Could not open one or more images.");
        exit -1;
    }
    size = cvGetSize(surfer);

    /* create a empty image, same size, depth and channels of others */
    result = cvCreateImage(size, surfer->depth, surfer->nChannels);
    cvZero(result);

    /* result = surfer + milkyway (NULL mask)*/
    cvAdd(surfer, milkyway, result, NULL);
 
    /* create a window, display the result, wait for a key */
    cvNamedWindow("example", CV_WINDOW_AUTOSIZE);
    cvShowImage("example", result);
    cvWaitKey(0);

    /* free memory and get out */
    cvDestroyWindow("example");
    cvReleaseImage(&surfer);
    cvReleaseImage(&milkyway);
    cvReleaseImage(&result);
    return 0;
}

/* gcc add.c -o add `pkg-config opencv --libs --cflags` */

Compile it (on a well configured OpenCV development environment) and run it:

gcc add.c -o add `pkg-config opencv –libs –cflags`
./add

The result got pretty cool, a milky way surfer.

surfer in the milk way

OpenCV: Edge Detection

This is a simple example of how pass edge detection in a video using OpenCV. It uses the built-in OpenCV Canny edge detector algorithm.

#include 
#include 
#include 

int main(int argc, char *argv[]) {
    int delay = 0, key=0, i=0;
    char *window_name;
    CvCapture *video = NULL;
    IplImage  *frame = NULL;
    IplImage  *grey  = NULL;
    IplImage  *edges = NULL;

    /* check for video file passed by command line */
    if (argc>1) {
        video = cvCaptureFromFile(argv[1]);
    } else {
        printf("Usage: %s VIDEO_FILE\n", argv[0]);
        return 1;
    }

    /* check file was correctly opened */
    if (!video) {
        printf("Unable to open \"%s\"\n", argv[1]);
        return 1;
    }

    /* create a video window with same name of the video file, auto sized */
    window_name = argv[1];
    cvNamedWindow(window_name, CV_WINDOW_AUTOSIZE);

    /* Get the first frame and create a edges image with the same size */
    frame = cvQueryFrame(video);
    grey  = cvCreateImage(cvGetSize(frame), IPL_DEPTH_8U, 1);
    edges = cvCreateImage(cvGetSize(frame), IPL_DEPTH_8U, 1);

    /* calculate the delay between each frame and display video's FPS */
    printf("%2.2f FPS\n", cvGetCaptureProperty(video, CV_CAP_PROP_FPS));
    delay = (int) (1000/cvGetCaptureProperty(video, CV_CAP_PROP_FPS));

    while (frame) {
	/* Edges on the input gray image (needs to be grayscale) using the Canny algorithm.
           Uses two threshold and a aperture parameter for Sobel operator. */
        cvCvtColor(frame, grey, CV_BGR2GRAY);
        cvCanny( grey, edges, 1.0, 1.0, 3);

	/* show loaded frame */
        cvShowImage(window_name, edges);
	
	/* load and check next frame*/
        frame = cvQueryFrame(video);
	if(!frame) {
		printf("error loading frame.\n");
		return 1;
	}

	/* wait delay and check for the quit key */
        key = cvWaitKey(delay);
        if(key=='q') break;
    }
}

To compile it in a well configured OpenCV development environment:

gcc edgeplayer.c -o edgeplayer `pkg-config opencv –libs –cflags`

To run it call edgeplayer and the name of the video:

./edgeplayer rick.avi

The result is something similar to this:

rick roll edge

CEJUG Tech Day 2009

ctd poster 50dpi

O Grupo de Usuários Java do Ceará estará realizando no próximo dia 04 de dezembro o CEJUG Tech Day na Fanor.

Este ano, precisamente nos dias 8 e 9 de dezembro, a Sun Microsystems estará realizando a edição 2009-2010 do Sun Tech Days, em São Paulo. Provavelmente será o último STD realizado. Felizmente, teremos mais uma vez um palestrante internacional da Sun, graças ao Maurício Leal, que organizou mais uma caravana dos palestrantes da Sun no Brasil.

Simon Ritter já esteve em Fortaleza participando do Café com Tapioca de Coco em 2008 e este ano palestrará sobre o futuro da JDK 7. Guilherme Silveira também participará e falará sobre REST e RESTful. Julio Viegas falará sobre infraestrutura e ambientes em Java de alta demanda e por fim, Josênio Cândido falará sobre o CMS Vignette.

Se você mora em Fortaleza não deixe de comparecer ao evento, a inscrição é gratuita com a adição de 2 quilos de alimentos não perecíveis que serão doados para instituições de caridade.

Código-fonte dos cartazes:

Simple Face Detection Player

Here’s a simple video player that also performs facial detection thought the Open Computer Vision Library.

Here’s a code developed using codes from nashruddin.com and samples from OpenCV, including the haar classifier xml. More detailed explanation on the theory about how the OpenCV face detection algorithm works can be found here.

The code:

#include 
#include 
#include 

CvHaarClassifierCascade *cascade;
CvMemStorage *storage;

int main(int argc, char *argv[]) {
    CvCapture *video = NULL;
    IplImage *frame = NULL;
    int delay = 0, key, i=0;
    char *window_name = "Video";
    char *cascadefile = "haarcascade_frontalface_alt.xml";

    /* check for video file passed by command line */
    if (argc>1) {
        video = cvCaptureFromFile(argv[1]);
    }
    else {
        printf("Usage: %s VIDEO_FILE\n", argv[0]);
        return 1;
    }

    /* check file was correctly opened */
    if (!video) {
        printf("Unable to open \"%s\"\n", argv[1]);
        return 1;
    }

    /* load the classifier */
    cascade = ( CvHaarClassifierCascade* )cvLoad( cascadefile, 0, 0, 0 );
    if(!cascade){
        printf("Error loading the classifier.");
	return 1;
    }

    /* setup the memory buffer for the face detector */
    storage = cvCreateMemStorage( 0 );
    if(!storage){
        printf("Error creating the memory storage.");
	return 1;
    }

    /* create a video window, auto size */
    cvNamedWindow(window_name, CV_WINDOW_AUTOSIZE);

    /* get a frame. Necessary for use the cvGetCaptureProperty */
    frame = cvQueryFrame(video);

    /* calculate the delay between each frame and display video's FPS */
    printf("%2.2f FPS\n", cvGetCaptureProperty(video, CV_CAP_PROP_FPS));
    delay = (int) (1000/cvGetCaptureProperty(video, CV_CAP_PROP_FPS));

    while (frame) {
	/* show loaded frame */
        cvShowImage(window_name, frame);
	
	/* wait delay and check for the quit key */
        key = cvWaitKey(delay);
        if(key=='q') break;
	/* load and check next frame*/
        frame = cvQueryFrame(video);
	if(!frame) {
		printf("error loading frame.\n");
		return 1;
	}

        /* detect faces */
        CvSeq *faces = cvHaarDetectObjects(
            frame, /* image to detect objects in */
            cascade, /* haar classifier cascade */
            storage, /* resultant sequence of the object candidate rectangles */
            1.1, /* increse window by 10% between the subsequent scans*/
            3, /* 3 neighbors makes up an object */
            0 /* flags CV_HAAR_DO_CANNY_PRUNNING */,
            cvSize( 40, 40 ) 
        );

        /* for each face found, draw a red box */
        for( i = 0 ; i < ( faces ? faces->total : 0 ) ; i++ ) {
             CvRect *r = ( CvRect* )cvGetSeqElem( faces, i );
             cvRectangle( frame,
                  cvPoint( r->x, r->y ),
                  cvPoint( r->x + r->width, r->y + r->height ),
                  CV_RGB( 255, 0, 0 ), 1, 8, 0 );
        }
    }
}

Yeah, I know the code needs a few adjustments. ¬¬

To compile it in a well configured OpenCV development environment:

gcc faceplayer.c -o faceplayer `pkg-config opencv ‑‑libs ‑‑cflags`

To run it you have to put in the same directory of the binary the XML classifier (haarcascade_frontalface_alt.xml) that comes with OpenCV sources at OpenCV-2.0.0/data/haarcascades/. And so:

./faceplayer video.avi

The results I got so far is that it works well for faces but sometimes its also detects more than faces. And here a video of it working live.

A example of good result:

rick roll face detection

A example of bad result:

rick roll face detection bad result

Maybe with some adjustments it could performs even better. But was really easy to create it using OpenCV.