Introduction of OpenCV Alireza Shirani Researcher of Medical Image and Signal Processing M. S Electrical Engineering yahoo. com Spring 1392

Outline Of Talking Introduction of OpenCV How to Install OpenCV Read & Write image & other related Function Read & Write video & other related Function

Introduction of OpenCV OpenCv (open computer vision ) library is library of programming function mainly aimed at real time computer vision developed by Intel and now supported by Willow Garage. It’s free for use under the open source BSD License OS Support: Windows,Android,Blackberry,Linux Distribution such as puppy, Ubuntu,…,Maemo,Free BSD,… Programming language OpenCv written in C++ and its primary interface is in C++.There are full interfacing Python, Java,MATLAB OpenCV can be used in Embedded Systems.

Read & Write image & other related Function Load Image: cvLoadImage The function cvLoadImage loads an image from the specified file and returns the pointer to the loaded image  IplImage* cvLoadImage(const char* filename, Parameters) Currently the following file formats are supported:  Windows bitmaps - BMP, DIB  JPEG files - JPEG, JPG, JPE  Portable Network Graphics - PNG  Portable image format - PBM, PGM, PPM  Sun rasters - SR, RAS  TIFF files - TIFF, TIF o Parameters : o CV_LOAD_IMAGE_COLOR the loaded image is forced to be a 3-channel color image o CV_LOAD_IMAGE_GRAYSCALE the loaded image is forced to be grayscale o CV_LOAD_IMAGE_UNCHANGED the loaded image will be loaded as is.

Read & Write image & other related Function IplImage is structure that contain all details about Image that was loaded

Read & Write image & other related Function Open window cvNamedWindow  cvNamedWindow(const char* name, int flags)¶¶ The function cvNamedWindow creates a window which can be used as a placeholder for images name – Name of the window in the window caption that may be used as a window identifier. flags – Flags of the window. Currently the only supported flag is CV_WINDOW_AUTOSIZE Delay in millisecondscvWaitKey  Int cvWaitKey(int delay=0) The function cvWaitKey waits for key event infinitely ( delay<=0) or for delay milliseconds. Returns the code of the pressed key or -1 if no key was pressed before the specified time had elapsed

Read & Write image & other related Function Release Space of RAMcvReleaseImage  void cvReleaseImage(IplImage* image)  Deallocates the image header and the image data image – Double pointer to the image header

Read & Write image & other related Function Create image cvCreateImage  IplImage* cvCreateImage(CvSize size, int depth, int channels)  Creates an image header and allocates the image data size – Image width and height depth – Bit depth of image elements. channels – Number of channels per pixel Point of image CvPoint  2D point with integer coordinates

Read & Write image & other related Function MoveWindoe cvMoveWindow(*name,x,y)  cvMoveWindow(const char* name, int x, int y) The function cvMoveWindow() changes the position of the window o x – New x coordinate of the top-left corner o y – New y coordinate of the top-left corner Convert Image cvConvertImage  cvConvertImage(const CvArr* src, CvArr* dst, int flags=0) Converts one image to another with an optional vertical flip src – Source image dst – Destination image The operation flags: CV_CVTIMG_FLIP - Flips the image vertically CV_CVTIMG_SWAP_RB - Swaps the red and blue channels. In OpenCV color images have BGR channel order, however on some systems the order needs to be reversed before displaying the image.

Read & Write image & other related Function Font setting in opencv cvInitFont  cvInitFont(CvFont* font, int fontFace, double hscale, double vscale, double shear=0, int thickness=1, int lineType=8)  The function initializes the font structure that can be passed to text rendering functions  font – Pointer to the font structure initialized by the function fontFace : CV_FONT_HERSHEY_SIMPLEX - normal size sans-serif font CV_FONT_HERSHEY_PLAIN - small size sans-serif font CV_FONT_HERSHEY_DUPLEX - normal size sans-serif font (more complex than  Hscale : Horizontal scale  Vscale: Vertical scale  param thickness : Thickness of the text strokes  param shear: Approximate tangent of the character slope relative to the vertical line. A zero value means a non-italic font. 1.0f means about a 45 degree slope, etc.  lineType : The function initializes the font structure that can be passed to text rendering functions.

Read & Write image & other related Function Write string on OpenCV cvPutText  void cvPutText(CvArr* img, const char* text, CvPoint org, const CvFont* font, CvScalar color)  The function renders the text in the image with the specified font and color img – Input image text – String to print org – Coordinates of the bottom-left corner of the first letter font – Pointer to the font structure color – Text color  CvScaler: is structure that contain R,G,B values of Pixels  Example CV_RGB(255,255,255) create white color

Read & Write image & other related Function Convert ImagecvCreateImage  IplImage* cvCreateImage(CvSize size, int depth, int channels)  Creates an image header and allocates the image data size – Image width and height depth – Bit depth of image elements. channels – Number of channels per pixel.

Read & Write image & other related Function Implements the Canny Algorithm cvCanny  void cvCanny(const CvArr* image, CvArr * edges, double threshold1, double threshold2, int aperture_size=3)  The function finds the edges on the input image and marks them in the output image edges using the Canny algorithm. image – Single-channel input image edges – Single-channel image to store the edges found by the function threshold1 – The first threshold threshold2 – The second threshold aperture_size – Aperture parameter for the Sobel operator

Read & Write image & other related Function Draws a line cvLine  cvLine(CvArr* img, CvPoint pt1, CvPoint pt2, CvScalar color, int thickness=1, int lineType=8, int shift=0)  The function draws the line segment between pt1 and pt2 points in the image img – The image pt1 – First point of the line segment pt2 – Second point of the line segment color – Line color thickness – Line thickness lineType – Type of the line: 8 - (or omitted) 8-connected line connected line. CV_AA - antialiased line. shift – Number of fractional bits in the point coordinates

Read & Write image & other related Function Draw circle cvCircle  cvCircle(CvArr* img, CvPoint center, int radius, CvScalar color, int thickness=1, int lineType=8, int shift=0)  The function draws a simple or filled circle with a given center and radius. img – Image where the circle is drawn center – Center of the circle radius – Radius of the circle color – Circle color thickness – Thickness of the circle outline if positive, otherwise this indicates that a filled circle is to be drawn lineType – Type of the circle boundary shift – Number of fractional bits in the center coordinates and radius value

Read & Write image & other related Function Smooth cvSmooth  cvSmooth(const CvArr* src, CvArr* dst, int smoothtype=CV_GAUSSIAN, int param1=3, int param2=0, double param3=0, double param4=0)  Function smooths an image using one of several methods. src – The source image dst – The destination image smoothtype – Type of the smoothing: CV_BLUR_NO_SCALE linear convolution with box kernel (all 1’s). If you want to smooth different pixels with different-size box kernels, you can use the integral image that is computed using Integral Integral CV_BLUR linear convolution with box kernel (all 1’s) with subsequent scaling by CV_GAUSSIAN linear convolution with a Gaussian kernel CV_MEDIAN median filter with a square aperture CV_BILATERAL bilateral filter with a square aperture

Read & Write image & other related Function Save Image cvSaveImage  int cvSaveImage(const char* filename, const CvArr* image)  The function cvSaveImagesaves the image to the specified file filename – Name of the file. image – Image to be saved

Read & Write video & other related Function capturing a video from a camera cvCaptureFromCAM  The functioncvCaptureFromCAMallocates and initializes the CvCapture structure for reading a video stream from the camera  CvCapture* cvCaptureFromCAM(int index)  index – Index of the camera to be used

Read & Write video & other related Function Extract frame from camera cvQueryFrame  Grabs and returns a frame from a camera or file  IplImage* cvQueryFrame(CvCapture* capture )  capture – video capturing structure

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