Image Processing Using Labview 4c2z72

Image Processing using LabVIEW By, Sandip Nair [email protected] sandipnair.hpage.com

What is image? • An image is two dimensional function, f(x,y), where x and y are spatial coordinates, and the amplitude, f at any pair of coordinates (x,y) is called the intensity or grey level of the image at that point. • I = [f{x,y}] where x = row index, y = column index f{x,y} is the pixel value at (x,y) location in image • for binary image f(x, y) = 0/1 where 0 = black, 1 = white • for gray scale image f(x, y) = 0 to 255 for 8 bit image where 0 = black, 255 = white • colored images are multi plane image

Image representation

Note: - Image representation is not same as the conventional coordinate system representation because an image is considered as a matrix and the matrix starts from the left top corner of the table as shown above

Digital image representation

Colored image representation • Colored image is defined by equation I = [s={x, y, n}] where n is the plane counter • Colored image can be of the following types: RGB = Red Green Blue HSL = Hue Saturation Luminance

Colored image representation

Image processing using Labview • Image processing in Labview is done in IMAQ vision toolkit and IMAQ vision builder • Imaq vision uses additional window for image instead of the front • Front does not offer any control or indicator for image

Labview basic image vi definition Image create: - allocates a memory location for an image Image dispose: - de-allocates the memory of an image before the program stops Image windDraw: - used for displaying image in image window

Image acquisition from webcam • go to in block diagram vision and motion>vision express>vision acquisition vi • select the integrated webcam from the list of drivers shown as shown in the next slide and follow the steps • after following the steps a vi gets created in the block diagram

Image processing • It is the manipulation done in an image when the output is an image • The following images gives an example of image processing

Image analysis • It is the manipulation done in an image when the output is not an image • It is the extraction of meaningful information from an image • Example: - Face recognition, bar code reading, object detection etc

Machine vision • Machine vision is termed for image processing and image analysis • Image processing and analysis done for high level application which come close to human vision capabilities of recognition

IMAQ vision assistant environment

IMAQ vision assistant environment • Image processing and analysis is done in the same window • The environment is divided into 3 sections: 1) Acquire images 2) Browse images 3) Process images

IMAQ vision assistant environment 1) Acquire images: Used to acquire images from the imaging device connected with the system. Can acquire single image or continuous images

IMAQ vision assistant environment 2) Browse images: Used to display a collection of images in memory in either full size or thumbnail

IMAQ vision assistant environment 3) Process image: Used to process the selected image. Process function can be accessed from the left column or from the top down menu of the window. During manual processing a script is generated which can be stored and can be used to process other images automatically. The script can be converted to equivalent vi from Tools>create labview vi. Thus vision assistant is useful to generate labview code without labview programming knowledge.

IMAQ vision assistant environment

Image acquisition • CCD cameras occupy the biggest area in the camera market • The sensor will have the same matrix similar to the image matrix • sensor data has to be collected -> data transferred over cable or other media serially -> rearranged to display it on the monitor

Charged coupled device (CCD) camera • CCDs consists of a number of photodiodes one for each pixel • Each photo detector is connected with mos capacitor • Every time the photo detector acquires a brightness value, it is stored in the capacitor • The values are shifted from one cell to another till it reaches the output

Principle functionality of CCD • Mos capacitor stores the charge Q generated by the corresponding detector for a certain time • The charge Q depends on the photo detector current IPH • IPH = S ᴓe where IPH = photo detector current S = light sensitivity ᴓe = light radiation power

CCD transfer mechanism