1. Interactive Input Methods & Graphical User Input

2. Learning Outcomes • Explain the 6 logical classifications of input devices • Differentiate the 7 interactive Picture Construction Techniques

3. Graphical Input Data • Types of input data: coordinate positions, attribute values, character-string specifications, geometric-transformation values, viewing conditions, illumination parameters. • Input procedures require interaction with display window managers & hardware devices.

4. Logical Classification of Input Devices Logical input device refers to input devices classified according to data type. • LOCATOR – specifies one coordinate position • STROKE – specifies a set of coordinate positions • STRING – specifies text input • VALUATOR – specifies a scalar value • CHOICE – specifies menu selection • PICK – specifies picture component selection

5. Locator Devices • Devices like mouse, joystick,trackball, are used for screen-cursor position • General purpose keyboards may have 4 or 8 cursor-control keys • Light pen used for interactive input of coordinate position

6. Stroke Devices • graphic tablet & continuous movement of mouse, trackball, joystick are used to input a sequence of coordinate positions

7. String Devices • primary physical device for string input is keyboard • other devices could generate character patterns that is recognized using stored dictionary of predefined patterns for specific application

8. Valuator Devices • valuator input is used to set scalar values for geometric transformations, viewing parameters & illumination parameters • panel of controls dials typically provides valuator input • display graphical representation of slider, buttons, rotating scales, menus • Joystick, trackball & keyboard could be adapted for valuator input by movement of the device relative to a scalar range

9. Choice Devices • menus are used to select processing options, parameter values & object shapes • touch panel, keyboard & voice entry are also common choice devices

10. Pick Devices • used to select part of a scene that is to be transformed or edited • using mouse, joystick or keyboard, picking the position of screen cursor to identify pixel coordinates • depending on type of object & complexity of scene, several levels of search required to identify pick object

11. Interactive Picture Construction Techniques • variety of interactive methods are incorporated into graphic package as aids in construction of pictures: 1) Basic Positioning Methods • interactively choose a coordinate position with a pointing device that records the screen location

12. Interactive Picture Construction Techniques 2) Dragging • select an object & drag it to a new location, thus object is then displayed in the new location. 3) Constraints • procedure for altering input coordinate values to obtain a particular orientation or alignment of an object • lines are constrained to have a particular slant • Input coordinates are constrained to lie along predefined paths

13. Interactive Picture Construction Techniques 4) Grids • rectangular grid displayed on screen area used to round input coordinates to nearest grid intersection • grids facilitate object construction when need to joins new line to an existing line endpoint. 6) Rubber-Band Methods • Line segments & other basic shapes constructed & positioned using rubber-band methods to be interactively stretched or contracted

14. Interactive Picture Construction Techniques 6) Gravity Field • to connect lines at positions between endpoints (that are not in grid intersections) graphic packages include procedure to convert any input position near a line segment into a position on the line using gravity field area around the line • any selected position within the gravity field of a line is “moved” to the nearest position on the line 7) Interactive Painting & Drawing Methods • freehand drawing uses curves generated by following the path of a stylus on a graphics tablet or path of the screen cursor on a video monitor

15. Designing a Graphical User Interface • Applications include GUIs composed of display windows, icons, menus, etc to aid user in applying the software to a particular problem • consideration for user interface area: • User Dialogue • Windows & Icons • Accommodating Multiple Skills Levels • Consistency • Minimizing Memorizing • Backup & Error Handling • Feedback