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# Chap30

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### Chap30

1. 1.  Relationship between image size & resolution for vector graphics and raster graphics.
2. 2. In This Chapter, you’ll learn on:  Define the term vector and raster graphics.  Compare the differences between raster and vector graphics in terms of o - image size o - Resolution (monitor display and print output) o - Quality o - Flexibility  Identify the various vector and raster graphic formats.
3. 3. Define the term vector and raster graphics There are two types of computer graphics – raster and vector. The raster graphic is composed of pixels and vector graphic is composed of drawing paths. Vector graphics  Vector graphics are made up of lines, curves, circles and shapes etc, defined by mathematical objects called vectors.  By following these instructions, the computer can create the variety of elements needed to form the shape of all objects in the image.  Vector graphics are often called object- oriented graphics.
4. 4.  These graphics retain their crispness whether they are resized, moved or have their colour changed.  Vector graphics are appropriate for illustrations, type, and graphics such as logos that may be scaled to different sizes.  Compared to raster images only the formulas are stored. This makes the size of the file very small. The images don't loose focus when you zoom, since the lines are re- rendered.
5. 5.  A vector image gives a very high quality, it requires small storage space and is easy to edit.  That's why you should always try to save your vector images in a vector format.  It is not possible to save photos, scanned images etc in a vector format.  Examples of vector images are drawings, diagrams and illustrations.  Picture 1 Enlargement of a vector image. The quality is still good.
6. 6.  Picture 1 Enlargement of a vector image. The quality is still good.  Picture 2 Enlargement of a vector image.
7. 7.  Raster graphics  A raster image is made up by small dots, known as pixels in different colors.  Each pixel is assigned a specific location and color value.  The dots create a pattern which forms an image which we called a bitmap (this is why raster graphics are also called bit-mapped graphics). In working with bitmap images, you edit groups of pixels rather than objects or shapes.  Picture 3 Enlargement of a raster image. The quality is not improved.
8. 8.  Drawings, photos, images etc, which shall be used in a document need to be transformed into a digital format.  This is done by scanning the image or takes a photo with a digital camera. The image is then stored as a raster file, i.e. dot-pattern image.
9. 9. Differences between raster and vector graphics  Computer graphics can be created as either raster or vector images. Raster graphics are bitmaps.  Raster graphics render images as a collection of countless tiny squares. Each square, or pixel, is coded in a specific hue or shade.  Raster graphics are best used for non-line art images; specifically digitized photographs, scanned artwork or detailed graphics.  Non-line art images are best represented in raster form because these typically include subtle chromatic gradations, undefined lines and shapes, and complex composition.
10. 10. Differences between raster and vector graphics  because raster images are pixel-based, they suffer image degradation.  Just like photographic images that get blurry and imprecise when blown up, a raster image gets jagged and rough. Although raster images can be scaled down more easily, smaller versions often appear less crisp or "softer" than the original.
11. 11. Differences between raster and vector graphics  Resolution in raster graphics is measured in dpi, or dots per inch. The higher the dpi, the better the resolution.  Better resolution, however, comes at a price. Just as raster files are significantly larger than comparable vector files, Overall, as compared to vector graphics, raster graphics are less economical, slower to display and print, less versatile and more unwieldy to work with.  Remember though that some images, like photographs, are still best displayed in raster format. Common raster formats include TIFF, JPEG, GIF, PNG and BMP files. Despite its shortcomings, raster format is still the Web standard -- within a few years, however, vector graphics will likely surpass raster graphics in both prevalence and popularity.
12. 12. Vector Graphics contains drawing directions, like drawing a circle etc. Raster image is not scalable. The image degrades when it is scaled to larger size. Differences between raster and vector graphics
13. 13. Differences between raster and vector graphics  Unlike pixel-based raster images, vector graphics are based on mathematical formulas that define geometric primitives such as polygons, lines, curves, circles and rectangles.  Because vector graphics are composed of true geometric primitives, they are best used to represent more structured images, like line art graphics with flat, uniform colors, logos, letterhead, and fonts.
14. 14. Differences between raster and vector graphics  The vector format has two big advantages over raster graphics:  (1) vector graphics area quickly and perfectly scalable, i.e., they can be can be resized and stretched without distortion; and  (2) vector graphics files are usually much smaller than bitmap files and thus use less memory in storage and less bandwidth in transmission. This makes them ideally suited for the World Wide Web.
15. 15. Differences between raster and vector graphics  Vector files tend to be considerably smaller than their raster counterparts. Overall, vector graphics are more efficient and versatile. Common vector formats include AI, EPS, FH, SWF, WMF etc.  Vector graphics are resolution-independent—thus, their resolution is determined only by the output device.
16. 16. Identify the various vector and raster graphic formats  Vector Graphics Formats: Some file formats, e.g. PDF, allow both raster and vector graphics. This is because the underlying PostScript system of the Portable Document Format is designed to handle both methods of creating graphics. Common Vector Graphics Formats File Extensions MIME type Proper name Description .ai Application/ illustrator Adobe Illustrator Document Vector format for Adobe Illustrator. .eps Image/eps Encapsulated PostScript A PostScript file that describes a small vector graphic, as opposed to a whole page or set of pages. .fh Application/Fr eehand Macromedia Freehand Document Vector format for Macromedia Freehand. .fla Application/Fl ash Flash Source File Shockwave Flash source file, only usable by Macromedia Flash authoring software.
17. 17. Identify the various vector and raster graphic formats Common Vector Graphics Formats File Extensions MIME type Proper name Description .pdf Applica tion/pdf Portable Document Format Fully supports vector graphics in a de facto standard format which can be read and printed on almost all operating systems. A much simplified version of PostScript allowing for files containing multiple pages and links. Works with Adobe Acrobat Reader or Adobe eBook Reader. .ps Applica tion/pos tscript PostScript Generic vector-based page description language, created and owned by Adobe. Postscript is a powerful stack-based programming language. Supported by many laser printers. .swf Applica tion/sho ckwave -flash Flash Flash is a web page plug-in that displays vector based animations contained in SWF files. Several applications can create SWF files; these include the Flash authoring tool from Macromedia. .wmf Image/ wmf Windows Metafile Stores vector graphics and raster graphics as a sequence of commands to be issued to the graphics layer of the Microsoft Windows operating system. (only partially vector)
18. 18. Identify the various vector and raster graphic formats  Raster Graphics Formats Some common raster graphic file formats are listed below. Common Raster Graphics Formats file extension MIME type proper name description .bmp Imag e/bm p Windows Bitmap Commonly used by Microsoft Windows programs, and the Windows operating system itself. Lossless compression can be specified, but some programs use only uncompressed files. .gif Imag e/gif Graphics Interchange Format GIF is used extensively on the web. Supports animated images. Supports only 255 colors per frame, so requires lossy quantization for full-color photos (dithering); using multiple frames can improve color precision. Uses lossless LZW compression, that used to make GIF avoided sometimes due to patent issues concerning LZW. .jpg Imag e/jpg Joint Photographic Experts Group JPEG is used extensively for photos and other continous tone images on the web. Uses lossy compression by trying to equalize eight by eight pixels; the quality can vary greatly depending on the compression settings.
19. 19. Identify the various vector and raster graphic formats  Raster Graphics Formats Some common raster graphic file formats are listed below. Common Raster Graphics Formats file extensio n MIME type proper name description .png Image/png Portable Network Graphics PNG is an image format with lossless compression, offering bit depths from 1 to 32. It was mainly designed to replace the use of GIF on the web. Free of the patent, which expired in 2003, associated with GIF. .psd Application/ Photoshop Photoshop Document Default proprietary format for Adobe Photoshop documents. Has many extra features such as image layering. Supported by very few image editing programs other than Adobe Photoshop. .tiff Image/tiff Tagged Image File Format TIFF is used extensively for traditional print graphics. Lossy and lossless compression available, but many programs only support a subset of available options.