Multimedia Programming 02:

Play with ImagesDepartments of Digital

ContentsSang Il Park

Announcement

• Homepage is now open!http://dasan.sejong.ac.kr/~sipark/class2007/mm

Outline

• OpenCV• How to start• Your first OpenCV code: HelloCV• Basic Functions• Pixel• Draw Lines or whatever you want• Conclusion

What is OpenCV?

• OpenCV– Stands for Open Source Computer Vision

Library– Includes 500 functions implementing

algorithms:• Computer vision• Image processing• General Purpose numeric algorithms

– Portable and efficient (C/C++)– Absolutely free!

Who did make this?

• Being developed at Intel since 1999• Available on Windows, Linux and MacOSX.• Extensively used in many companies and

research centers

• Home page: www.intel.com/technology/computing/opencv/

OpenCV

• OpenCV– Intended Applications

• Computer Human Interaction (HCI)• Object Identification• Segmentation and Recognition• Face Recognition• Gesture Recognition• Motion Tracking• Motion Understanding• And so on.

Where you can find this

• http://sourceforge.net/projects/opencvlibrary• http://sourceforge.net/project/showfiles.php?

group_id=22870&package_id=16937

OpenCV structure

CXCOREbasic structures and algoritms,XML support, drawing functions

CVImage processing

and vision algorithms HighGUIGUI, Image and Video I/O

We will mostlyfocus on these twoin this presentation

HelloCV: Your First OpenCV Code

Loading an image and showing it

Make a new project

• Start Visual Studio 6.0 or Visual Studio .Net

• Make a new project– Win32 Console Application Program

• Compile and run it! (Ctrl + F5)

Initial Setup

• Directories:– Includes:

• "C:\Program Files\OpenCV\cv\include" "C:\Program Files\OpenCV\cxcore\include" "C:\Program Files\OpenCV\otherlibs\highgui“

– Libraries:• "C:\Program Files\OpenCV\lib“

• Library files you need:– cv.lib cxcore.lib highgui.lib

Initial Setup

• Include Directories (toolsoptions):• "C:\Program Files\OpenCV\cv\include"

"C:\Program Files\OpenCV\cxcore\include" "C:\Program Files\OpenCV\otherlibs\highgui“

Initial Setup

• Library Directories: (toolsoptions)• "C:\Program Files\OpenCV\lib“

Initial Setup

• Library files you need:– cv.lib cxcore.lib highgui.lib

Initial Set up

• Include Header files – #include <cv.h>

#include <cxcore.h> #include <highgui.h>

HelloCV

• Type this: #include "stdafx.h"#include <cv.h>#include <cxcore.h>#include <highgui.h>

int _tmain(int argc, _TCHAR* argv[]){

IplImage * img;img = cvLoadImage("d:\\test.jpg");

cvNamedWindow("HelloCV");cvShowImage("HelloCV", img);

cvWaitKey();

cvDestroyWindow("HelloCV");cvReleaseImage(&img);

return 0;}

http://dasan.sejong.ac.kr/~sipark/class2007/mm/code/hellocv.cpp

Error!

• Copy every dll files – from: C:\Program Files\OpenCV\bin– To: under your debug folder

HelloCV

HelloCV

#include "stdafx.h"#include <cv.h>#include <cxcore.h>#include <highgui.h>

int _tmain(int argc, _TCHAR* argv[]){

IplImage * img;img = cvLoadImage("d:\\test.jpg");

cvNamedWindow("HelloCV");cvShowImage("HelloCV", img);

cvWaitKey();

cvDestroyWindow("HelloCV");cvReleaseImage(&img);

return 0;}

http://dasan.sejong.ac.kr/~sipark/class2007/mm/code/hellocv.cpp

• IplImage

• cvLoadImage• cvReleaseImage

• cvNamedWindow

• cvShowImage• cvDestroyWindo

w

• cvWaitKey

Image structure

• IplImage (Image Processing Library)• typedef struct _IplImage {

int nSize; /* size of iplImage struct */int ID; /* image header version */int nChannels;int alphaChannel;int depth; /* pixel depth in bits */char colorModel[4];char channelSeq[4];int dataOrder;int origin;int align; /* 4- or 8-byte align */int width;int height;struct _IplROI *roi; /* pointer to ROI if any */struct _IplImage *maskROI; /*pointer to mask ROI if any */void *imageId; /* use of the application */struct _IplTileInfo *tileInfo; /* contains information on tiling*/int imageSize; /* useful size in bytes */char *imageData; /* pointer to aligned image */int widthStep; /* size of aligned line in bytes */int BorderMode[4]; /* the top, bottom, left, and right border mode */int BorderConst[4]; /* constants for the top, bottom,left, and right border */char *imageDataOrigin; /* ptr to full, nonaligned image */

} IplImage;•

Image I/O IplImage* cvLoadImage(image_path,

colorness_flag);loads image from file, converts to color or grayscle, if need, and returns it (or returns NULL).

image format is determined by the file contents.#define CV_LOAD_IMAGE_COLOR 1 #define CV_LOAD_IMAGE_GRAYSCALE 0 #define CV_LOAD_IMAGE_UNCHANGED -1 DEFAULT

cvSaveImage(image_path, image);saves image to file, image format is determined from extension.

cvReleaseImage(image_path, image);releases memory

BMP, JPEG, PNG, TIFF, PPM/PGM formats are supported.IplImage* img = cvLoadImage(“picture.jpeg”,-1);if( img ) cvSaveImage( “picture.bmp”, img );

Windows

• cvNamedWindow(window_name, fixed_size_flag);creates window accessed by its name. Window handles repaint, resize events. Its position is remembered in registry:cvNamedWindow(“ViewA”);cvMoveWindow(“ViewA”,300,100);cvDestroyWindow(“ViewA”);…

• cvShowImage(window_name, image);copies the image to window buffer, then repaints it when necessary. {8u|16s|32s|32f}{C1|3|4} are supported.

only the whole window contents can be modified. Dynamic updates of parts of the window are done using operations on images, drawing functions etc.

• cvDestroyWindow(window_name);deletes the window with the given name

User Input

• int cvWaitKey( int delay=0 )waits for a pressed key. After waiting for the given delay, it proceeds. Zero delay means waiting forever until user input. – Delay in milliseconds.

• Good for animating something

• Example) swapping between two images

What else HighGUI can do?• “Smart” windows• Image I/O, rendering• Processing keyboard and other events, timeouts• Trackbars• Mouse callbacks• Video I/O

Pixel Accessing

• Image Coordinate System

• Color Value: CvScalar– A container for 1-,2-,3- or 4-tuples of numbers – typedef struct CvScalar { double val[4]; } CvScalar;

• Example) CvScalar s;s.val[0] = 200; (Blue)s.val[1] = 11; (Green)s.val[2] = 123; (Red)

x

y (0,0)(8,2)

Pixel Accessing

• CvScalar cvGet2D (image, y, x)Gets color value at (x,y). – Example) CvScalar s;

s = cvGet2D(img, 30, 40);

• void cvSet2D (image, y, x, CvScalar)Sets color value at (x,y).– Example) CvScalar s = cvScalar(100,0,0);

cvSet2D(img, 30, 40, s);OR

cvSet2D(img, 30, 40, cvScalar(100,0,0));

ORcvSet2D(img, 30, 40,

CV_RGB(0,0,100));

Create an empty canvas

• IplImage* cvCreateImage( CvSize size, int depth, int channels ); – Depth: color depth: IPL_DEPTH_8U – Channels: 1,2,3,4 (1=grey, 3=color)– Example)

IplImage * img; img = cvCreateImage(cvSize(200,100), IPL_DEPTH_8U,3);

• cvSet(image, CvScalar)– Fill canvas with a color– Example)

cvSet(img, CV_RGB(255,255,255));

So far what you’ve learned:

• IplImage• cvLoadImage (file_name)• cvCreateImage (size, depth, channels)• cvSaveImage (file_name, image)• cvReleaseImage (image)• cvNamedWindow (window_name)• cvShowImage (window_name, image)• cvDestroyWindow (window_name)• cvWaitKey (delay)• cvGet2D (image, y, x)• cvSet2D (image, y, x, cvScalar)

Put everything together!int _tmain(int argc, _TCHAR* argv[]){

IplImage * img;img = cvLoadImage("d:\\test.jpg");

cvNamedWindow("HelloCV");cvShowImage("HelloCV", img);cvWaitKey();

int x,y;for(x=0; x<100; x++)

for(y=0; y<100; y++){

CvScalar s = cvGet2D(img, y,x);s.val[0] +=50; s.val[1] +=50; s.val[2] +=50;cvSet2D(img,y,x,s);

}

cvShowImage("HelloCV", img);cvWaitKey();

cvDestroyWindow("HelloCV");cvReleaseImage(&img);

return 0;}

HelloCV2.cpp

A Simple Function: Line Drawing• Horizontal line drawing:

– void DrawHLine(IplImage * img, int y, int st, int ed, CvScalar color)

image

Do more!

• Design a function that draws a rectangle– void DrawRectangle

(IplImage * img, int x, int y, int w, int h, CvScalar color)

– Don’t forget to make sure a pixel is inside the image

• 0 <= max_x <= img->width• 0 <= max_y <= img->height

• If done, try to draw 50 random boxes with random colors!

(x,y) w

h

For those who want more

• OpenCV Wiki-pages: http://opencvlibrary.sourceforge.net

• For HighGUI:– http://opencvlibrary.sourceforge.net/HighGui

• For cxcore:– http://opencvlibrary.sourceforge.net/CxCore

• Supplied documentation: OpenCV/docs/index.htm, faq.htm

• A Korean Community: http://www.opencv.co.kr/

Program Assignment #1

• Long long times ago in Russian Empire– Sergei Mikhailovich Prokudin-Gorskii

(1863-1944)– A man who pursuing

a colorful future in 1907

http://www.loc.gov/exhibits/empire/

Program Assignment #1

• His invention

A camera His camera

Program Assignment #1

• His pictureswith the current digital technology

Program Assignment #1

• Recover the colorful world in 1907 by yourself!

1I31I3

1I3

align

B

G

R

Program Assignment #1

• 4 Images can be found in the class homepage:– http://dasan.sejong.ac.kr/~sipark/class2007/

mm/

• Make a team of two students• Due date: 9/11 before the class

– Submit a written report and email the codes and a execution file

• Type the filename in the cmd window, then generate a color image!

• Grading Policy:– Making a color image: 60– Automatic alignment: 40