Image enhancement software for underwater recovery operations
Contents
1. 17 Unzoom seca a a e e 18 Sharpen V 19 Low Pass Filter 20 An Edge Detector ETE 21 Image Averaging cen na saman ea DPP PPP U U U SS QUICK REFERENCE LIST soseer aa I A for select mem A oee a a co dolor S en 9 9 come eee 9 an ja 9 EE M ees 9 a 9 eT cT 9 d we SHOUTS OTT TCI 9 5o 9085077 9 CAE 9 40r ana a 0304 9 _ a 9 gt gt gt er ES m RR hm 10 10 d TU 11 S ERR ER RII htm 11 PUSPA LT 11 2 li 0 a 11 oo acs Uu co nume CU 11 ELE us EN to ERR IR oe ee ea suwUY 11 II 2 12 table gt2. 12 DT 2 539272 7 7 27 2127 cena ww ke 12 00 R j 12 1 12 d IER m RR RR Re 12 I 000 12 Ew v oramegrabber off and exit program 12 DIGITAL IMAGE PROCESSING PRIMER 13 SO ee GENERAL THE DIGIT THE El LI a s eo o o o 9 o A GENERAL The Menu software package 15 a menu driven program which provides real time continuous video image processing using lookup table modification techniques It also provides limited non real time single frame enhancement capability Control of the routines in Menu varies from manual requiring operator input to make an adjust ment to automatic or hands off operation The processing routines were chosen to provide maximum effectiveness in situations where the images pixel values are limited to a relatively small region of the total grav scale range Typically this would include images of objects which have actual small variations in s
3. 562 89 023 NAVAL POSTGRADUATE SCHOOL Monterey California TECHNICAL REPORT Image Enhancement Software for Underwater Recovery Operations User s Manual William J Partridge Charles W Therrien 16 June 1989 Approved for public release distribution unlimited Prepared for Naval Undersea Weapons Engineering Station FedDocs Keyport WA 98345 D 208 1M 2 NPS 62 89 023 I 81 L SCHOOL om IPTORN1A 93945 5002 j Eh ddd NAVAL POSTGRADUATE SCHOOL 5 Monterey California Rear Admiral R W West Jr Dr Harrison Shull Superintendent Provost Reproduction of all or part of this report is authorized This report was prepared in conjunction with research conducted for Naval Undersea Weapons Engineering Station and funded by the Naval Postgraduate School CLASS OF TH 6 PAGE mnr ny KNOX LIBRARY REPORT DOCUMENTATION PAGE 0 15 RESTRICTIVE MARKINGS AU 2 05943 800 wi REPORT SECURITY CLASSIF CATION UNCLASSIFIED SECURITY CLASS FICATION AUTHORITY DEC ASSIFICATION DOWNGRADING SCHEDULE 3 OISTRIBUTION AVAILABILITY OF REPORT 3 5 MONITORING ORGANIZATION REPORT NUMBER S NPS 62 89 023 ERFORIMING ORGANIZATION REPORT NUMBER S NAME OF PERFORMING ORGANIZATION Naval Postgraduate School OFr CE SYMBOL 7a NAME OF MONITORING ORGANIZATION
4. Naval Undersea Weapons Engineering Station ADDRESS City State and ZIP Monterey CA 93943 7b ADDRESS City State and ZIP Code Keyport WA 98345 I NAME OF FUNDING SPONSORING 85 OFFICE SYMBOL 9 PROCUREMENT INSTRUMENT IDENTIFICATION NUMBER ORGANIZATION If applicable val Postgraduate School O amp MN Direct Funding ADDRESS City State ana 21 Code 10 SOURCE O FUNDING NUMBERS PROGRAM PROJECT TASK WORK UNIT onterey CA 93943 ELEMENT NO NO NO ACCESSION NO hue include Security Classirication Image Enhancement Software for Underwater Recovery Operations User s manual PERSONAL AUTHOR S William J Partridge Charles W Therrien TYPE Or REPORT 3b TME COVEPED 14 DATE OF REPORT Year Month Day 15 PAGE COUNT FROM 6 88 _ 10 6 89 16 June 1989 SUPPLEMENTARY NOTATION ESSA CODES FIELD GROUP SuB GROUP ABSTRACT Continue on reverse if necessary and identify by block number 18 SUBJECT TERMS Continue on reverse if necessary and identify by block number video image enhancement image processing underwater recovery underwater viewing This report describes software for performing image enhancement on live or recorded video images The software was developed for operational use during underwater recovery operations at the Naval Undersea Warfare Engineering Station The image processing is performed on an IBM PC AT compatible computer equipped with hardware to digitize and displa
5. Table Stretch INITIAL DISTRIBUTION LIST Defense Technical Information Center Cameron Station Alexandria VA 22304 6145 Library Code 0142 Naval Postgraduate School Monterey CA 93943 5002 Department Chairman Code 62 Department of Electrical and Computer Engineering Naval Postgraduate School Monterey Califorma 93943 Professor W Therrien Code 62 Department of Electrical and Computer Engineering Naval Postgraduate Schoo Monterey California 93943 Professor Roberto Cristi Code 62 Department of Electrical and Computer Engineering Naval Postgraduate School Monterey California 93943 meoressor M Fargues Code 62 Department of Electrical and Computer Engineering Naval Postgraduate School Monterey California 93943 Professor Ralph Hippenstiel Code 62 Department of Electrical and Computer Engineering Naval Postgraduate School California 93943 Professor Murali Tummala Code 62 Department of Electrical and Computer Engineering Naval Postgraduate School Monterey California 93943 Mr Richard Evans me ES Code 7021 Naval Undersea Weapons Engineering Station Kevport Washington 98345 17 Opies tJ 10 DE 14 CDR NUWTES Code 80 Naval Undersea Weapons Engineering Station Kevport Washington 98345 Mr Alan L Lindstrom L5 Code 70 Naval Undersea Weapons Engineering Station Kevport Washington 98345 Professor O B
6. a default register base address of 100 To change the FrameGrabber board insert a jumper at location J11 Again if 100 is not used the chosen value will have to be entered each time Menu 15 run I an AT host 1s being used a jumper is required at location J20 If an XT or PC 1s being used no jumper should be installed at J20 2 Installing the Board Pages 3 1 through 3 3 of the FrameGrabber Manual provide a detailed de scription for installing the board A summary 15 as follows e Turn off and unplug the computer and periphials Remove the cover e Place the board in any open slot where it fits and install screws Reinstall cover e Plug in and turn on computer 3 Cable Installation Page 3 5 of the Frame Grabber Manual shows how to connect the cable Here s the bottom line e Plug the rectangular female connector on the cable into the top connector protruding from the board e Connect the white labeled BNC connector to the video source output Connect the green labeled BNC connector to the line input not the green input of the red green blue connections Do not connect the red or blue labeled cables 4 Running the Diagnostics Page 3 10 of the Frame Grabber Manual describes the procedure for running the diagnostic software included with the Frame Grabber Since the factory configura tion has been changed as described above the command lt configure gt will have to be entered followe
7. default Now hit the L key for computation of linear lookup table histogram After the COMPUTING HISTOGRAM indicator goes away hit M for computation of modified histogram When the indicator goes away this time D to display the linear lookup table histogram This 15 the infor mation used to perform the equalization The image on the video monitor is the un processed version Now hit E to display the modified histogram The video image is enhanced and the spread out histogram is displayed As you toggle back and forth between D and you can see graphically how equalization lets us use the full range of intensitv levels and the corresponding enhancement of contrast on the image Con vinced Hit the S key and let s trv something else 12 Modifying the Lookup Table Hit the key Now we ll go again to the number pad with Num Lock on Using the corner keys 1 3 7 and 9 we ll change the slope of the lookup table by moving the top or bottom of the curve To shallow out the lookup table use the 9 key to move the top to the right and the I key to move the bottom to the left Notice that enhancement to the live images changes as you modify the curve When you are finished hit S to stop and the resulting lookup table is shown If you were to develop a fa vorite lookup table which vou think vou might want to use again there is a way to save it in the computer We ll talk about that la
8. display mem A and snap routines to get one Now hit the A key to select memory A This selects memory A for data manipulations or storage For our purposes we have selected the image data in memory A to store on disk Now hit the I key and you will be asked to enter an image name Type a name e g to store the image on the current disk and directory or path and name e g image to store it in a different place Then you ll be prompted for a comment You may give it a label or simply type none note that lt enter is required for each of these inputs The disk drive selected should make some noise and your snapshot is safely tucked away in the photo album i e the image file is written to the disk 8 Open the Album to See Your Snapshot Let s see if the image was really saved First erase both frame memories as described in paragraph 5 or 6 above Then select a memory using or 8 Now hit the J key Type the image file name followed by lt enter gt to read the image from disk The image should appear on the video monitor If it does not display the memory you selected the C or D key and the image will appear 9 Simple Processing Now let s process real time video images using some simple lookup table mod ification techniques the 17 key its called analysis but reallv it just lets vou see how vour image is being changed The graph you see on your computer monitor 15 the current lo
9. live action from your camera VCR if you re using a tape make sure you press the play button first 3 Take a Snapshot Now let s freeze the action Hit for snap This acquires and displays a single frame You should see a stop action snapshot on your video monitor The image 15 also stored now in framegrabber memory A the default memory chosen when vou started up 4 Take Two Snapshots Now hit D for display memory B Take another snapshot with the F key The second snapshot is now displayed on the monitor and stored in framegrabber memory B Try going back to memory A the C key to make sure the first snapshot is still there Note that we are using the display memory keys and not the select memory keys to perform these operations More on select memory later when we start storing images 5 All Black Let s erase of our snapshots Display memory B the D key and then hit the G key for screenclear O This clears the screen and framegrabber memory to black or intensity level zero 6 All White While still in memory B hit the key for screenclear 255 This erases the screen and memory B to white or intensity level 255 Darker gray shades have lower intensity levels while lighter shades have higher intensity levels 7 Put Your Snapshot in the Photo Album Saving an image to disk 1s analogous to putting your snapshot in a photo al bum You should still have an image in frame memory A If not use the
10. makeup of a digital image including the concept of pixels and how gray level shading is accomplished It also describes the histogram a basic tool in the analysis of a digital image Finally it introduces the lookup table which is the primary image processing tool used in the Menu program B THE DIGITAL IMAGE Think about a black and white photograph Suppose you were to overlay a grid on it which is 512 squares across by 512 squares down The picture is divided into 512 x 512 262 144 tiny squares Each square 15 called a pixel Now look at an individual pixel to see what color it is If it 15 black it will be assigned the lowest number intensity level 0 If it is white it will be assigned the highest number intensity level 255 Different shades of gray will be assigned intensity levels between 0 and 255 with lower numbers for darker grays and higher numbers for lighter grays Once the image has been broken up into pixels and each pixel has been assigned an intensity level it is said to be digitized It s intensity levels are then stored in order somewhere in the computer In the case of the framegrabber it is placed into frame memory either A or B for processing and or passing on to the monitor C THE HISTOGRAM Now let s look at our digitized image and count how many black pixels intensity level 0 are in it Then we ll count the dark dark grays intensity level 1 the dark grays intensity level 2 and so on all the way up to
11. menu Hit the O key to select the output lookup table Then go back into analysis You may now use any of the lookup table modification routines e g invlut abslut etc and you will get a piggybacked lookup table effect on the im age To get back to normal hit L to linearize the output lookup table Go back to the main menu and select and linearize the input lookup table Note that when you use this procedure always put values derived by equalization into the input lookup table or the equalization will be based on already modified data 16 Zoom Now hit the R key to start the zoom function On the video monitor you can see the rectangle we saw before Using the number pad with Num Lock on you can move the rectangle with the 2 4 6 and 8 keys in the direction of the arrows on the keys The size of this one is fixed at approximately one quarter of the screen since we will be expanding the image to four times the original Move the rectangle to the por tion of the image vou wish to zoom in on and hit S The expanded image is displayed Notice that some resolution is lost from the original because we are Zooming digitally as opposed to changing the focal length of the camera lens Hit M to get back to the menu Now you can process the zoomed image using the fixed image processing rou tines described below 17 Unzoom To return to a normal image after using the zoom routine and performing a
12. move the rectangle around on the screen The corner numbers 1 3 7 and 9 are used to change the size of the rectangle If your image had a large white or black area in which you were not interested it would lessen the impact of the equalization routine on the area of in terest So you would frame the area of interest with the rectangle After you have placed the rectangle where you want it hit S for stop Now you have to choose between manual or automatic update Try manual update first Hit the key The image will equalize the new lookup table is plotted and live action continues using the new lookup table In this mode as you notice the contents of the image changing you can the U key and equalization will occur again Let s go back now and the default rectangle parameters C to change parameters Now D for default and for continuous update You are prompted for time between updates in seconds Enter any number 2 through 9 The computer will perform a new equalization at the interval you specify This is intended for situ ations where the contents of the image are changing often and you don t want to have to remember to update When you have seen enough updates hit S for stop 11 Before and After Let s look at some histograms and see whats happening when we equalize Hit the H key for histogram Again you may choose between default or rectangle to specify a portion of the image Hit D for
13. the whites intensity level 255 When we are finished we will have analvzed the image with respect to gray level content A plot of this gray level content is called a histogram A histogram is normally plotted as a bar graph with the intensity levels 0 to 255 plotted across the bottom and the number of pixels which have each intensity plotted as a vertical bar see figure 1 The Menu program has a routine which allows you to compute and display the histogram ofan image The histogram values are also used in an important lookup table modifi cation technique the histogram equalization 13 Figure 1 Example of Histogram D THE LOOKUP TABLE A lookup table provides a way to change all pixels of a particular intensity level to another intensity level The table has 256 possible input values one for each possible gray level in the original image and a corresponding output value for each input Lookup tables are normally plotted graphically with the input values across the hori zontal axis and the corresponding output values on the vertical axis A lookup table whose output values are the same as it s input values will not change the image and is called a linear lookup table It plots as a straight line from the lower left corner to the upper right corner of the lookup table graph as shown in figure 2 An inverse lookup table changes black pixels to white white pixels to black and in between values to their difference from 255 The im
14. Wilson Department of Physics Naval Postgraduate School Monterev California 93943 MAJ William J Partridge Student Detachment U S Command and General Staff College Fort Leavenworth Kansas 66027 Research Administration CODE 012 Naval Postgraduate School Monterey CA 93943 DUDLEY KNOX LIBRARY 1 00347355 4 w
15. age processed through the inverse lookup table looks like a s negative We refer to it as a negative image The inverse lookup table plots as a straight line from the upper left corner to the lower right corner of the graph as shown in figure 3 A lookup table stretch is performed by setting low and or high valued intensity lev els to zero and stretching the reduced input range of values to a full scale output range 14 OUTPUT 208 Figure 2 A Linear Lookup Table The resulting graph 1s a straight line with a steeper slope than our original linear lookup table see figure 4 and the image will have overall enhanced contrast the steeper the slope the greater the contrast but for a smaller range of input values A more powerful nonlinear form of stretching the lookup table is the histogram equalization technique It performs localized stretching of the lookup table by detecting the areas of the histogram which have few or no pixel counts and using them to stretch high pixel count areas across Histogram equalization is a very efficient means of con trast enhancement The Menu program is based primarily on lookup table modifica tion techniques and provides the user with the capability to modify the lookup table in many different ways including those described above i OUTPUT 208 188 B 188 288 INPUT Figure 3 Inverse Lookup Table OUTPUT 208 188 4 188 208 INPUT Figure d Lookup
16. conjunction with P select input lookup table al lows for processing through two modified lookup tables 16 P to select input lookup table Selects the input lookup table to perform modifications on and for display in the analvsis routine When used in conjunction with O select output lookup table allows for processing through two modified lookup tables 17 Q for zoom Enlarges chosen area of image Provides moveable rectangle to select area for zoom With Num Lock on use number pad keys 2 4 6 and 8 to move rectangle down left right and up respectively Hit Z to stop rectangle and fix zoom image m to return to main menu 18 R for unzoom Returns image to normal state 19 S for sharpen Sharpens fixed image using a high pass filter May be used on zoomed image 20 T for low pass Performs a low pass filter operation on a fixed image Reduces high frequency noise Blurs the image May be used on zoomed image 21 U for edge detector Performs Sobel edge detector operation on a fixed image Displays detected edges Mav be used on zoomed image 22 V for image average Averages specified number of image frames and displays results Prompts input of number of frames to average 23 W for framegrabber off and exit program Terminates program 12 APPENDIX A DIGITAL IMAGE PROCESSING PRIMER A GENERAL This appendix provides the reader with some background on the basics of digital image processing It describes the
17. d by the register base address 100 and the memory base address D0000 The diagnostics take several minutes to run so be patient As stated in the manual system memory or other devices mapped into the same memory space or regis ter addresses will cause some tests to fail D LET S TRY IT OUT This is an introduction to the Menu program It let s vou walk through some of the features of the program sort of a hands on familiarization If you are not famuliar with some of the concepts described in this section or with digital image processing in general you should probably have a look at the Primer which is included in this docu ment as an appendix It explains the neccessary ideas in just a few pages Now turn on your source camera or VCR and video monitor to let them warm up On your computer go to the directory where you want to keep the program and copy Enenu exe there 1 Load the Program To get started simply type the word menu followed by enter No lt en ter gt is needed for any selection from here on out unless otherwise noted The menu should now be displayed on the computer monitor If you are not using the memory base address 00000 and register base address 100 as described in paragraph C above hit K to change setup and follow the instructions on your monitor 2 Live Action Menu selection E provides continuous acquisition and display of the incoming real time video images Hit E and you should see
18. erforms equalization and lookup table modification routines Options as follows m modlut Modifies lookup table by drawing lines Places pointer on video monitor Move pointer to desired start point and end point using Num Lock on and number keys 2 4 6 and 8 for down left up and right respectively Use keys Il 7 9 and 3 for faster movement down left up and right respectively 1 b beginline Marks beginning of line 2 e endline Marks end of line 3 d drawline Draws line and enters new values into lookup table 4 p pointer Places pointer on video monitor Gives pointer location and pixel intensity level of that location on computer monitor Use same method to move pointer as for line drawing routine above 5 s stop Exit lookup table modify routine b n 2 lut Changes slope of existing lookup table and implements results With Num Lock on use number pad keys 1 and 3 to move bottom of curve left and right re spectively Use 7 and 9 keys to move top of curve left and right respectively s to exit this routine c h histogram Computes and displays histograms for images processed with linear and modified lookup tables Snaps images before and after processing and allows for com parison 1 d default Selects default portion of image for histogram computa tion approximately 90 of image 2 r rectangle Displays rectangle
19. hading or those whose contrast has been reduced by obscuration or dim lighting B EQUIPMENT REQUIRED The following equipment 15 required to use the Menu program e IBM Personal Computer AT XT or PC or 100 compatibles with Extended Graphics Adaptor card and monitor e Imaging Technology PCVISIONplus Frame Grabber card with standard cable 2 NOTE The older model PCVISION Frame Grabber will not work e Analog video monitor such as SONY Trinitron3 Model 1271Q e Video source camera or video tape player ES SIMPLE SETUP The PCVISIONplus Frame Grabber User s Manual provides all the information required to place the Frame Grabber into operation Here 1s a much condensed version of that procedure with some helpful hints to ease the way l Getting the Board Ready Figure 2 1 on page 2 2 of the Frame Grabber Manual shows the jumper lo cations on the board and Table 2 1 on page 2 3 tells how they are configured from the factory There are three position functions to be concerned with e Since an EGA card is needed to run Menu the memory base address must be changed on the Frame Grabber board Address D0000 is recommended since this is the default value in the software To change to address D0000 simply insert a jumper at location J8 If other than 00000 is chosen it should be noted for entry each time Menu is run 1 Trademark of IBM 2 Trademark of Imaging Technology Inc 3 Trademark of SONY e Menu has
20. m s options in the order they appear with a brief de scription of their output 1 A for select mem A Selects framegrabber memory A for storing or reading an image to from disk t B for select mem B Selects framegrabber memory B for storing or reading an image to from disk 3 for display mem A Selects framegrabber memory A for acquisition of image from camera and dis plays memory A on the monitor 4 D for display mem B Selects framegrabber memory B for acquisition of image from camera and dis plays memory B on the monitor S Efor grab Continuously acquires image frames from source and displays on video monitor Uses framegrabber memory designated by display mem function 6 F for snap Acquires a single frame from source and displays it on the video monitor Uses framegrabber memorv designated by display mem function 7 for sclear 0 Clears screen and memory to intensity level 0 8 for sclear 255 Clears screen and memory to intensity level 255 9 Ito store image Stores contents of selected memory to disk Prompts input of filename includ ing path if desired and comment 10 J to read image Reads image from disk file to selected framegrabber memory Prompts input of filename including path if desired II K to change setup Allows change of software memory base address and register base address On screen instructions and example inputs provided 12 L for analysis Displays lookup tables and histograms P
21. nt processing algorithms to a captured frame The report is in the form of a user manual for the software and includes guided tutorial and reference sections A Digital Image Processing Primer in the appendix serves to explain the principle concepts that are used in the image processing TABLE OF CONTENTS GENERAL de o1 EQUIPMENT REQUIRED SIMPLE SETUP Em n a US l Getting the Board Ready 2 Instaling the Board a aa pp P C W 3 Cable Installation H I 4 Running the Diaenostics 7 LET S I Load the Program Live Action Take a SnapsWot 2 Take Two Snapshots TP All Black a a White aooi aoi tuaa eae a Put Your Snapshot in the Photo Alum TJ QN S Open the Album to See Your Snapshot m 9 Simple Processing _ 10 Histogram Equahzation 00200 m TM ll Before and Alter e a 12 Modifying the Lookup Table TU 13 Draw Your Own Lookup Table aa a 14 Storing and Retrieving Your Favorite Lookup Tables m 15 Piggyback Lookup Tables am 16 Zoom
22. ny fixed image processing hit the R key It is essential that this be done when vou finished with a zoomed image or the zoom parameters will interfere with other rou tines 18 Sharpen Snap an image by hitting the F key or by using the zoom routine the key Then hit S to sharpen it If you watch closely you can see the sharpening occurring on the displaved image 19 Low Pass Filter Snap or zoom another image and then hit T to call the low pass filter routine This function is designed to remove high frequency noise from a fixed image Again looking closely you can see the change occurring 20 An Edge Detector One more time snap or zoom an image This time hit the C Kev to perform a Sobel Edge Filter Note the interesting display of the image 5 edges on the video monitor 2 Image Averaging Hit the key Then enter the number of image frames you want to average together This number may be limited by the amount of disk space you have available 2 1s a good number to start with When the average image 15 displayed vou should notice that objects which passed across the field of view during the operation have faded away The more frames vou average the less visible these objects will become Image averaging is very effective at eliminating transient noise but requires a stable platform for the source To exit the program hit the W key E QUICK REFERENCE LIST This list presents the progra
23. okup table The horizontal coordinate represents input pixel values and the vertical represents output values On the top of the computer monitor screen are the current options available for selection The snap and grab CC options work the same as on the previous menu Try them Now try the invlut 1 option and see how the lookup table changes the blue line is the current lookup table and the green is a reference linear lookup table line The effect on the image 1s just like looking at the negatives of a photograph except that we still have live action Now hit the L key for linear lookup table We back to unprocessed live images Kevs P logarithmic and A absolute value also modify the lookup table You can experiment with these functions to see the effect on the real time image and their corresponding lookup table shape 10 Histogram Equalization Now for the most powerful of our lookup table modification routines Hit E for equalize You now are given two choices default and rectangle This determines which portion of the image will be used to do the processing Most of the time vou will probably use the default mode but let s try rectangle now just for fun Hit R for rectangle On the video monitor you will see the live images being displaved with a rectangle overlaid Now hit Num Lock on your keyboard Using the 2 4 6 and 8 keys on the number pad the ones with the arrows you can
24. okup table at specified intervals Prompts for desired interval Hit s to exit equalization routine from this mode 4 m manual update Selects lookup table update on command a u update Performs new equalization and updates lookup table b c changeparam Returns to default rectangle portion of image options for changing parameters c f freezeframe Acquires and displays a single frame snap d g grab Continuous acquisition and display of image frames e s stop Exit equalization routine from this mode e l Sets lookup table to linear values Results in unprocessed image f i invlut Sets lookup table to inverse values Produces a negative 1mage loglut 75 Sets lookup table to logarithmic values Increases image brightness h a abslut Inverses intensitv levels greater than 127 Reduces image brightness i g grab Continuous aquisition and display of image frames j f freeze Aquisition and displav of a single frame snap k s stop Exit analysis routine 13 M to store lookup table Stores contents of selected lookup table to disk Prompts input of filename including path if desired 14 N to read lookup table Reads lookup table values from disk to lookup table they were stored from Prompts input of filename including path if desired 15 to select output lookup table Selects the output lookup table to perform modifications on and for display in the analysis routine When used in
25. superimposed on image on video monitor Change portion of image used for histogram computation by altering rectangle size and location With Num Lock on use number pad keys 2 4 6 and 8 to move rectangle down left right and up respectively Use 1 and 3 keys to increase and decrease height Use 7 and 9 keys to increase and decrease width Hit 5 to exit rec tangle routine 3 l com linhist Computes histogram of image processed by linear LUT Displays COMPUTING HISTOGRAM message until done 4 m modhist Computes histogram of image processed by modified LUT Displays COMPUTING HISTOGRAM message until done 5 d dis linhist Displays histogram computed above using image processed by linear lookup table Unprocessed image shown on video monitor 6 e dis modhist Displays histogram computed above using image processed by modified lookup table Processed image shown on video monitor 7 s stop Exit histogram routine 10 d e equalize Performs histogram equalization with update on command or automatically at specified intervals Displavs resulting lookup table after each update 1 d default Selects default portion of image to use for equalization approximately 90 of image 2 r rectangle Allows use of rectangle to specify portion of image to be used as described in histogram rectangle routine above paragraph 12 c 2 3 c continuous update Selects automatic update of lo
26. ter 13 Draw Your Own Lookup Table Now hit MI to perform another form of manual lookup table modification We ll do this by drawing lines Using the number pad with Num Lock on move the pointer on the computer monitor by hitting the 2 4 6 and 8 keys This will move it one pixel in the direction of the arrows on the keys The next key clockwise from each of these will move it in the same direction ten pixels e g The 1 key moves the pointer in the same direction as the 2 key only faster When the pointer is at a location where vou want the line to begin hit B for begin line Then move the pointer to a location where vou want the line to end and hit E for end line Now hit D to draw the line and vour change will take effect on your image You may draw other lines to connect segments and build a whole new lookup table To get rid of the clutter just hit 5 and then reenter the routine by hitting Now hit P to put a pointer on the live video image To move the pointer use the number pad kevs in the same manner as vou did to move the pointer on the com puter monitor described above Notice on your computer monitor that the position of the pointer and the intensity level are displayed One possible use of this capability would be to find the intensity level of an object in the image and use the draw lookup table routine to change all pixels with that intensitv to another level Again if you were to dra
27. w a really good all purpose lookup table you could save it with a routine which we ll describe later Hit S to exit the video monitor pointer routine and S again to exit the modify routine Finally let s go back to the main menu to see the lookup table storage selection routines and try some single frame frozen processing Type 5 to exit the analysis function 14 Storing and Retrieving Your Favorite Lookup Tables Remember that lookup table you designed using the modify routine a while ago Here s how you can save it for future use Hit the MI key Type in a name e g mylut a mylut hit enter and the values are saved To get it back hit the N key to read the lookup table values from disk Again type in the file name followed by enter and your lookup table will take effect 15 Piggyback Lookup Tables The framegrabber board has two sets of lookup tables one as the image is put into frame memory and one as the image is output to the monitor Up to this point we have only used the output lookup table Now we ll modify both sets to achieve dif ferent result Hit the P key to select the input lookup table Then go back to the analysis routine L and do a histogram equalization Everything still looks the same as the last time we equalized including the video image but this time the computed values went into the input lookup table Now exit the equalization and analysis routines to get back to the main
28. y video images The software provides the capability to provide contrast enhancement and other similar functions in real time through hardware lookup tables to automatically perform histogram equalization to capture one or more frames and average them or apply one of several different processing algorithms to a captured frame The report is in the form of a user manual for the software and includes guided tutorial and reference sections A Digital Image Processing Primer in the appendix serves to explain the principle concepts that are used in the image processing EJ UNCLASSIFIED UNLIMITED C same as RPT DTIC USERS a NAME OF RESPONSIB INDIVIDUAL 22b TELEPHONE Include Area Code lt 2c OFFICE SYMBOL mc All other editions are obsolete ft U S Government Printing Office 1986 606 24 ABSTRACT This report describes software for performing image enhancement on live or recorded video images The software was developed for operational use during underwater recov ery operations at the Naval Undersea Warfare Engineering Station The image process ing 1s performed on an IBM PC AT compatible computer equipped with hardware to digitize and display video images The software provides the capability to provide con trast enhancement and other similar functions in real time through hardware lookup tables to automatically perform histogram equalization to capture one or more frames and average them or applv one of several differe
Download Pdf Manuals
Related Search