MA/CS 375

1. MA/CS 375 Fall 2002 Lecture 24 MA/CS 375

2. Matlab functions ginput • ginput is a Matlab function which takes one argument • input: number of points to select in the image • output: x and y MA/CS 375

3. Matlab functions ginput Cross hairs appear, then click to select point. MA/CS 375

4. interp2 • ZI = INTERP2(X,Y,Z,XI,YI) interpolates to find ZI, the values of the underlying 2-D function Z at the points in matrices XI and YI. • Matrices X and Y specify the points at which the data Z is given. • Out of range values are returned as NaN. • X, Y must be a regular grid of data (i.e. created with meshgrid) MA/CS 375

5. Matlab functions interp2(interpolation of rectangular array data) MA/CS 375

6. griddata • griddata does the same as interp2 however the input data can be given at arbitrarily spaced points. • ZI = GRIDDATA(X,Y,Z,XI,YI) fits a surface of the form Z = F(X,Y) to the data in the (usually) nonuniformly-spaced vectors (X,Y,Z) • GRIDDATA interpolates this surface at the points specified by (XI,YI) to produce ZI. The surface always goes through the data points. • XI and YI are usually a uniform grid MA/CS 375

7. Matlab functions griddata MA/CS 375

8. Team Project • Introduction • Each team is going to work on the same type of project. • All presentation rules for homework apply to the team project. • All coding must be done in Matlab MA/CS 375

9. General Project Topic • Image tweening. • i.e. given two or more images we are going to write routines that create intermediate images • Morphing using non-linear maps • Examples… • More details: MA/CS 375

10. Part 1 • Devise a one page team plan • It should address what part each team member will work on MA/CS 375

11. Board demo Part 2 • Load in two images using imread • Crop the images to be the size of the smaller image. • Display the images in the same window using subplot • Let the “user” select a set of control point pairs [CXleft,CYleft] and [CXright,CYright]. i.e. a control point pair consists of one 2D point from each picture. Use ginput • Plot a * at each point in the left picture and a + at each point in the right picture, using plot MA/CS 375

12. Part 3 • Use griddata to evaluate: Xwarpleft = griddata(CXright,CYright,CXleft,Xright,Yright, ‘cubic’); Ywarpleft = griddata(CXright,CYright,CYleft,Xright,Yright, ‘cubic’); where Xright and Yright are a rectangular grid of pixel locations in the right hand image, created with meshgrid. The output Xwarpleft and Ywarpleft indicate the coordinates in the left image where the color of each pixel in the final right image is going to be found Try using ‘linear’, ‘cubic’, ‘v4’ (i.e. first, third and mystery order interpolation) Make sure the calculated Xwarpleft and Ywarpleft are in bounds MA/CS 375

13. Part 4 • For each pixel in the right picture, use the coordinates (Xwarpleft,Ywarpleft in the left picture) found in Part 3, and the function interp2 to find the three intensities (red, green and blue) in the left picture at the warped coordinates. • Convert the results into unsigned 8-bit integers using uint8. • Use image to plot the deformed picture. MA/CS 375

14. Example Green points map to red points  warped coordinate system MA/CS 375

15. Part 5 • Using linear interpolation in time, plot a sequence of tween images (t=0,0.2,0.4,..,1) using: • C(x,y) = LeftImage((1-t)*Xleft+t*Xwarpleft,(1-t)*Yleft+t*Ywarpleft) • Where the values of LeftImage are obtained with interp2 MA/CS 375

16. Example of Tweening MA/CS 375

17. Part 6 • Using linear interpolation in time (t=0, 0.2, …, 1.0), plot a sequence of tween images using: • C(x,y) = LeftImage((1-t)*Xleft+t*Xright,(1-t)*Yleft+t*Yright) • THEN: Using linear interpolation in time (t=0, 0.2, …, 1.0), plot a sequence of tween images using: • C(x,y) = (1-t)*LeftImage(Xwarpleft,Ywarpleft)+t*RightImage(Xright,Yright) MA/CS 375

18. Part 7 • Each team member should contribute a picture. • Using the same method as Part 6 create an animation of the pictures morphing from one to the other in sequence. MA/CS 375

19. Part 8 (extra credit) • Create a graphical user interface for the project using guide • It should have a number of buttons, sliders, radio buttons e.g. • a slider to choose the number of control points • a file option to choose the left and right images • an option to add and reduce control points • a zoom option • a slider to choose number of tween frames • …. • Go wild…. MA/CS 375

20. Matlab functions guide • Type guideat the matlab prompt: http://www.mathworks.com/access/helpdesk/help/techdoc/creating_guis/creating_guis.shtml MA/CS 375

21. guide cont(adding a slider) • click on slider icon • move mouse to top left of required slider • drag rectangle tospecify shape ofslider • click File, then save as (1) (2) (3) MA/CS 375

22. guide cont.(enabling a slider button) • right click on slider button • left click on properties • you can now edit the properties of this slider MA/CS 375

23. Using handles > fig = openfig(mfilename,'reuse'); > handles = guihandles(fig); % Create structure for the first time > slider_value = get(handles.slider1, ‘Value); MA/CS 375

24. Add A Bunch of Options(but design a better interface) MA/CS 375

25. Running GUI: MA/CS 375

26. Checking slider value MA/CS 375

27. Project Due 10/23/02 • No extensions. Presentations due on 10/23 • I encourage you to get the majority of it working well before the due date !!. • Each team member must submit their own report, preferably with experiments using their own pictures. MA/CS 375