Multimedia Programming 02: Play with Images Departments of Digital Contents Sang Il Park

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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:

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

OpenCV structure CXCORE basic structures and algoritms, XML support, drawing functions CV Image processing and vision algorithms HighGUI GUI, Image and Video I/O We will mostly focus on these two in 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 (tools  options): "C:\Program Files\OpenCV\cv\include" "C:\Program Files\OpenCV\cxcore\include" "C:\Program Files\OpenCV\otherlibs\highgui“

Initial Setup Library Directories: (tools  options) "C:\Program Files\OpenCV\lib“

Initial Setup Library files you need: –cv.lib cxcore.lib highgui.lib

Initial Set up Include Header files –#include #include #include

HelloCV Type this: #include "stdafx.h" #include 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; } hellocv.cpp

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

HelloCV

#include "stdafx.h" #include 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; } hellocv.cpp IplImage cvLoadImage cvReleaseImage cvNamedWindow cvShowImage cvDestroyWindow 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)); OR cvSet2D(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 width 0 height If done, try to draw 50 random boxes with random colors! (x,y) w h

For those who want more OpenCV Wiki-pages: For HighGUI: – For cxcore: – Supplied documentation: OpenCV/docs/index.htm, faq.htm A Korean Community:

Program Assignment #1 Long long times ago in Russian Empire –Sergei Mikhailovich Prokudin-Gorskii ( ) –A man who pursuing a colorful future in

Program Assignment #1 His invention A cameraHis camera

Program Assignment #1 His pictures with the current digital technology

Program Assignment #1 Recover the colorful world in 1907 by yourself! 1I3 align B G R

Program Assignment #1 4 Images can be found in the class homepage: – Make a team of two students Due date: 9/11 before the class –Submit a written report and 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