Getting started with Imalab and Scheme - PRIMA

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¨¨2.1 Options-p starts in scheme mode, default is c++ mode. This option needs to stand before the other options.-ia starts in interactive mode (no imalab screen is initialised).-ppm, -tiff, -jpeg, -mpeg gives the image/sequence format.-dir name gives the directory where the images/sequences are searched.-file name specifies a file that contains the image filenames. 1 per line.-screen columnline columnline is a 2 digit number, -screen 31 gives a screen with 3 columns and¢¡£¤1¦¥line.Default is -screen 22. The screen positions are §numbered as follows:-load name loads the file name and executes it.-v verbose mode. Prints information on loaded files.Imalab has different modes:interactive mode: you can type commands in the shell. The default interaction language is c++ like. If youspecify the option -p, the interaction language is scheme. You can switch from c++ to scheme by typingscheme in the shell.continuous mode: the imalab screen is active. This mode has two sub modes.– movie mode: This mode displays an image sequence. The space key allows to switch between moviemode and step mode. Typing q switches to interactive mode.– step mode: the imalab screen is active. Single images are displayed. You can navigate through the imagesof a sequence by using the arrows of your keyboard. The space key switches to movie mode.2.2 Example Imalab commandsimalab -p -ia -ppm starts in scheme mode, interactive mode, and uses images in ppm format. No images arespecified by this command: you will load images manually. The -p option needs to be placed before the other options.Dis-imalab -p -ppm -dir name starts in scheme mode, uses all images with .ppm extension in name.plays the images as a sequence (continuous movie mode). For interaction with screen see section 2.3.imalab -p -mpeg2 /home/desdemona/hall/Walk1.mpg starts imalab in continuous movie modewith sequence Walk1.mpg. To go to interactive mode, type q while mouse is in imalab screen. For interaction withscreen see section 2.3.svideod-mpeg play -ab5 -- -dither color /home/desdemona/hall/Walk1.mpgimalabcreates a video daemon from a .mpg file (you might want to define an alias). This displays a toolbar on your screen.Click pause, rewind. Then start imalab. Imalab without arguments starts imalab in continuous movie mode with asequence given by the video daemon that must be running. An error is produced, if the video daemon is not running.svideod -d/dev/video1 -ab5imalabfirst start video daemon with camera on device /dev/video1, then start imalab. Imalab without arguments starts imalabin continuous movie mode with a sequence given by the video daemon that must be running. An error is produced, ifthe video daemon is not running.(continue) switches from interactive mode to continuous mode.2
(quit) ends imalab. This is equivalent to ctrl-d.Interrupt execution: type ctrl-c. If this does not get you back to the shell, type ctrl-c twice again.2.3 Imalab screenInteraction with the imalab screen are possible in continuous mode, not in interactive mode. To switch to continuousmode type (continue). For screen interaction, place the mouse cursor within the imalab screen window. Use thekeyboard to type commands.q quits continuous mode, goes to interactive mode. Typing (continue) in the shell brings you back to continuousmode.space switches between step mode and movie mode. The current-image and the following images are displayed.arrow up displays frame(t-10) (in step mode). The image cache is by default set to 60 images.arrow down displays frame(t+10) (in step mode)arrow right displays frame(t+1) (in step mode)arrow left displays frame(t-1) (in step mode)mouse click displays circle in all windows (in step mode)3 Basic SchemeA scheme expression can either be a variable or a procedure call.variablename displays the value stored in the location to which the variable is bound.A scheme command is structured as follows: opening parenthesis, function name followed by 0 or several parameters,closing parenthesis. This is true without exception; in particular, arithmetic operators are just functions. Examples:(function no params)(function with 1 parameter param1)(function with 2 parameters param1 param2)Parameters can be anything, numbers, variable names, functions, ... . Typical examples are:(list) function with no parameters, creates an empty list(sin 1.0) function with 1 numerical parameter, computes the sine of 1.0(* 2 5) function with 2 numerical parameters, computes product of 2 and 5(define a 0.0) function with 2 parameters, assigns the value 0.0 to a variable named a(+ 1 4.0 3.2) function with 3 (or more parameters), computes the sum of the parameters.Scheme functions always give a value, which may be of any type: in cases of numerical calculations this is the result.In other cases, the return value can be an object (i.e. an image, a list) or a boolean (#t notes true, and #f notes false).The return value of a function can be assigned to a new variable as follows:(define empty list (list)) initialises a variable with name empty list and assigns the return value of(list) to it.3
Page 1: Getting started with Imalab and Sch
Page 5 and 6: (stringify obj) converts object obj
Page 7 and 8: arguments, try (help ClassName Func
Page 9 and 10: ¨¨¨SchemeC++(define c (+ a b)) c
Page 11: Follow the instructions in exhelp.s

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