1. CS- 375 Graphics and Human Computer Interaction Lecture 1: 12/4/1435 Fundamental Techniques in Graphics Lecturer: Kawther Abas

2. 2 Angel: Interactive Computer Graphics 5E © Addison-Wesley 2009 Computer Graphics Computer graphics deals with all aspects of creating images with a computer –Hardware –Software –Applications

3. 3 Angel: Interactive Computer Graphics 5E © Addison-Wesley 2009 CRT Can be used either as a line-drawing device (calligraphic) or to display contents of frame buffer (raster mode)

4. Computer Graphics “Computer graphics refers to using a computer to create or manipulate any kind of picture, image, or diagram.”,with a graphics editing program –MS Paint –Adobe Photoshop –GIMP –Etc.

5. Bitmapped Graphics There are two basic types of graphics: –Bitmapped and and Vector Bitmapped graphics are much more common Often they are called raster graphics When you create a bitmapped graphic you are basically creating a bunch of colored dots The bitmapped graphic is stored as an array of dots, or pixels each pixel gets assigned a specific color The more pixels you have, the more detailed the image can be

6. 6 Angel: Interactive Computer Graphics 5E © Addison-Wesley 2009 Raster Graphics Image produced as an array (the raster) of picture elements (pixels) in the frame buffer

7. bitmap graphics programs Some common bitmap graphics programs are: 1.Photoshop 2.Paint Shop Pro 3.GIMP 4.Photo-Paint 5.Graphic Converter These are paint programs

8. Vector Graphics Vector graphics are created and manipulated using drawing programs (as opposed to paint programs for bitmapped graphics) Instead of using pixels to describe the image, it describes the image using shapes Circles –Lines –Curves Also has to store the color of these shapes

9. The programs used with vector graphics Some of these programs include: –Corel Draw –Adobe Illustrator –Acrobat Most of these programs allow the use of bitmapped images as part of a vector image

10. Bitmap vs. Vector Images Bitmap and vector images are obviously different Both have strengths and weaknesses They don’t manipulate images in the same way They don’t store images in the same way The images are edited differently

11. Bitmap Images 1.Very flexible –Any image can be represented (with enough pixels) 2.Created by scanners, digital cameras, and other similar devices 3.Used most commonly, especially on the web 4.Can be displayed directly on your computer screen if 1 image pixel is the same size as 1 screen pixel 5.Takes a lot of memory –The color of each pixel must be stored –Can be compressed

12. Vector Images 1.Easy to change parts of the image since each part is stored as a different shape 2.Can manipulate the image smoothly –Rotating, changing color, size, line width, etc. 3.Limited to the shapes the program can handle 4.Typically takes less memory and disk space than a bitmap 5.Must be converted to a bitmap to display

13. File Formats Each way of storing an image is called a file format Hopefully, you’re familiar with JPEG and GIF file formats. You can’t just rename “somepicture.gif” to “somepicture.jpg” and expect to get the desired result –Can’t just rename a.doc file as.ppt and expect a presentation out of it Images have to be converted from one file format to another

14. Common File Formats Bitmap Formats GIF: graphics interchange format JPEG: joint photographic experts group PNG: portable network graphic BMP: Windows bitmap TIFF: tagged image file format Vector Formats SVG : scalable vector graphics EPS: encapsulated postscript CMX: Corel meta exchange PICT: Macintosh Picture WMF: Windows metafile

15. It is an attribute of objects (like texture, shape, smoothness, etc.) Color is a sensation produced by the human eye and nervous system. It depends on: 1) spectral characteristics of the light source(s) (e.g., sunlight) illuminating the objects (relative spectral power distribution(s) SPD) 2) spectral properties of objects (reflectance) 3) spectral characteristics of the sensors of the imaging device (e.g., the human eye or a digital camera) What is color?

16. The Two Most Common Color Models: - RGB model (Red-Green-Blue) - CMYK model (Cyan-Magenta-Yellow-blacK) Color Model * Types of Color model.

17. 1)RGB Color Model: * Additive color model. * For computer displays. * Uses light to display color. * Colors result from transmitted light. * Red + Green + Blue = White. Color Model * Types of Color model.

18. 2) CMYK Color Model: * Subtractive color model. * For printed material. * Uses ink to display color. * Colors result from reflected light. * Cyan + Magenta + Yellow = Black. Color Model * Types of Color model.