Multimedia Production Lecture 4 Digital Image Dr. Somsak Phattarasukol Faculty of Management Science UDON THANI RAJABHAT UNIVERSITY Digital Graphics Image ● In computer graphics, there are two types of digital graphics images: – A raster image – A vector image Source: Wikipedia.org Raster Image ● A raster image is a dot-matrix data structure representing a grid of pixels, or points of color. – A pixel is the smallest controllable element of a picture represented on the screen Source: Wikipedia.org Vector Image ● A vector image is a graphics created from geometrical primitives such as points, lines, curves or polygons (all of which are based on mathematical expressions). – Vector graphics are based on vectors (also called paths), which lead through locations called control points or nodes. Source: Wikipedia.org Raster vs Vector An vector image can be magnified infinitely without loss of quality, while a raster image cannot. Source: Wikipedia.org Raster vs Vector Since computer monitors and printers are raster devices, a vector image need to be converted to a raster image before being displayed or printed. Source: Wikipedia.org Raster vs Vector ● A raster image is a collection of pixels, thus its file size is positively correlated to the number of pixels and the color depth (bits per pixel). – For example, a 640 * 480 pixel image with 24-bit color would occupy almost a megabyte of space: 640 * 480 * 24 = 7,372,800 bits = 921,600 bytes Source: Wikipedia.org Raster vs Vector ● A vector image is a collection of geometric descriptions, thus its file size is independent of the image dimension and increases only with the addition of more vectors. Source: Wikipedia.org Image File Compression ● There are two types of image file compression algorithms: – Lossless compression and – Lossy compression. Source: Wikipedia.org Lossless Compression ● Lossless compression algorithms reduce file size while preserving a perfect copy of the original uncompressed image. – Lossless compression generally, but not always, results in larger files than lossy compression. – Lossless compression should be used to avoid accumulating stages of re-compression when editing images. Lossy Compression ● Lossy compression algorithms reduce file size by discarding some details of the original image. – Often lossy compression is able to achieve smaller file sizes than lossless compression. – Most lossy compression algorithms allow for variable compression that trades image quality for file size. Source: Wikipedia.org Image File Formats ● Image file formats can be separated into the two main families: – Raster: JPEG, TIFF, RIF, GIF and PNG – Vector: CGM and SVG Source: Wikipedia.org JPEG ● JPEG (Joint Photographic Experts Group) – JPEG applies lossy compression to images. – The degree of compression can be set and have an effect on the visual quality of the result. – JPEG files suffer generational degradation when repeatedly edited and saved Source: Wikipedia.org TIFF ● TIFF (Tagged Image File Format) – TIFF can apply lossy or lossless compression to images. – TIFF remains widely accepted as a photograph file standard in the printing business. – TIFF files is not widely supported by web browsers. Source: Wikipedia.org RIF ● RIF (Raw Image Format) – A raw image file contains minimally processed data from the image sensor of digital cameras and therefore are not ready to be printed or edited. – RIF usually use a lossless (or nearly lossless) compression, and produce file sizes smaller than the TIFF format. – The raw formats are not standardized or documented, and differ among camera manufacturers. Source: Wikipedia.org GIF ● GIF (Graphics Interchange Format) – GIF is most suitable for storing graphics with few colors, such as simple diagrams, shapes, logos and cartoon-style images – GIF uses LZW lossless compression (which is more effective when large areas have a single color, and less effective for photographic images). – GIF includes animation capabilities and is still widely used to provide image animation effects. Source: Wikipedia.org PNG ● PNG (Portable Network Graphics) – PNG provides a patent-free replacement for GIF (though GIF is now patent-free), and can also replace many common uses of TIFF. – PNG applies lossless compression to images. – PNG provides file integrity checking and detection of common transmission errors, and is the most used lossless image format on the Internet. Source: Wikipedia.org CGM ● CGM (Computer Graphics Metafile) – CGM contains instructions and data for reconstructing technical graphics. – CGM is still prevalent in engineering, aviation, and other technical applications but has largely been superseded by formats such as SVG and DXF. – CGM is not widely supported for web pages. – W3C has developed WebCGM, a profile of CGM intended for the use of CGM on the Web. Source: Wikipedia.org SVG ● SVG (Scalable Vector Graphics) – SVG is an open standard created by W3C to address the need for a vector format for the web. – SVG is suitable for high quality, creative graphics with strong requirements for color, text, font features, animation, and filter effects on raster portions. – The SVG format does not have a compression scheme of its own, but due to the textual nature of XML, can be compressed using any file compression program. Source: Wikipedia.org Raster Graphics Editors ● Raster graphics editors are computer programs that allow users to create and edit raster images interactively on the computer screen: – Adobe Photoshop, and – GIMP Source: Wikipedia.org Adobe Photoshop ● Adobe Photoshop is a raster graphics editor developed by Adobe Systems. – It was created in 1988 by Thomas and John Knoll and has become the standard in raster graphics editing. – In 2004, with the introduction of Creative Suite branding, each new version of Photoshop was designated with "CS" suffixes. – In June 2013, with the introduction of Creative Cloud branding, its licensing was changed to “software as a service” and its suffixes were changed to "CC". Source: Wikipedia.org GIMP ● GIMP (GNU Image Manipulation Program) is a free and open-source raster graphics editor. – It started in 1995 as a school project of two university students and has become a full-fledged application. – It can be used for image retouching and editing, free- form drawing, resizing, cropping, photo-montages, converting between different image formats. – It is expandable and extensible with plug-ins and extensions to improve and enhance its functionality. Source: Wikipedia.org Image Editing Operations ● Raster graphics editors support various image editing operations: – Select a region for editing. – Draw lines with simulated brushes of different color, size, shape and pressure. – Fill a region with a single color, gradient of colors, or a texture. – Select a color using different color models. – Edit and convert between various color models. Source: Wikipedia.org Image Editing Operations ● Raster graphics editors support various image editing operations: – Add typed letters in various font styles. – Remove imperfections from photo images. – Composite editing using layers. – Apply filters for effects including sharpening and blurring. – Convert between various image file formats. Source: Wikipedia.org Perspective Control Source: Wikipedia.org Sharpening Source: Wikipedia.org Contrast Correction Source: Wikipedia.org Color Adjustment Source: Wikipedia.org Totorials Source: Adobe.com Tutorials Source: Adobe.com Tutorials ● Links to tutorials from Adobe TV – http://tv.adobe.com/show/learn-photoshop-cs5 – http://tv.adobe.com/watch/learn-photoshop-cs5/gs08-m aking-a-hohum-raw-image-great-/ – http://tv.adobe.com/watch/creative-suite-podcast-photogr aphers/how-to-use-the-photoshop-cs5-patch-tool-to-fix-th ings-in-portrait-retouching/ Source: Adobe.com.