DOCSLIB.ORG

Lecture 02 Image and Graphics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Lecture 02 Image and Graphics MULTIMEDIA TECHNOLOGIES LECTURE 02 IMAGE AND GRAPHICS IMRAN IHSAN ASSISTANT PROFESSOR THE NATURE OF DIGITAL IMAGES An image is a spatial representation of an object, a two‐dimensional or three-dimensional scene or another image. Often the images reflect the intensity of lights. Most photographs are called continuous‐tone images because the method used to develop the photograph creates the illusion of perfect continuous tone throughout the image. Images stored and processed by computers, displayed on computer screens, are called digital images although they often look like continuous‐tone. This is because they are represented by a matrix of numeric values each represents a quantized intensity values. • Basic Concepts • The smallest element on a digital image is known as a pixel— a picture element. A digital image consists of a (usually rectangular) matrix of pixels. Width Height DEPTH The depth of an image is the number of bits used to represent each pixel. 1‐bit black‐and‐white image, also called bitmap image. 4‐bit can represent 16 colors, used in low resolution screens (EGA/VGA) 8‐bit can have 256 colors. The 256 color images are often known as indexed color images. The values are actually indexes to a table of many more different colors. For example, Color 3 is mapped to (200, 10, 10). 8‐bit grey 256 grey‐levels. The image contains only brightness / intensity data without color information. DEPTH 16‐bit can have 65536 colors, also known as hi‐color in Windows systems. The 16 bits are divided into 5 bits for RED, 6 bits for GREEN & 5 bits for BLUE. 24‐bit 224 = 16,777,216 colors, true color. Each byte is used to represent the intensity of a primary color, RED, GREEN and BLUE. Each color can have 256 different levels. 32‐bit 232 = 4,294,967,296 (4G). Usually, 3 bytes are used to represent the three primary colors and the fourth byte is used as the alpha channel. DEPTH RESOLUTION Resolution measures how much detail an image can have. There are several resolutions relating to images. Image resolution is the number of pixels in an image. 320 X 240 = 76800 pixels 700 X 400 = 280000 pixels Display (Monitor) resolution — refers to number of dots per inch (dpi) on a monitor. Windows systems usually have 96dpi resolution. Some high resolution video adapters/monitors support 120dpi. For example, a 288 X 216 image displayed on a monitor with 96dpi will be 3” X 2 ¼”. Output resolution — refers to number of dots per inch (dpi) on a (hard copy) output device. Many printers have 300dpi or 600 dpi resolution. High‐quality image setters can print at a range between 1200dpi and 2400dpi, or higher. The above image printed on a 300dpi printer will be 0.96 X 0.72 inch. ACQUIRING DIGITAL IMAGES There are many ways to create or get digital images. We list a some of the most common ways: • Make an image from scratch with a paint program. A good program will allow you to choose the depth, resolution and size. • Grab an image of a screen. The depth, g p , resolution and size is determined by the screen. • Capture an image from a digital camera or a camcorder. The depth, resolution and size is determined by the camera or the camcorder. The popular depth is 24‐bit. • The commonly used resolution is 320 X 240, 640 X 480 and 800 X 600. • Scan a photograph or a print using a scanner. You can select from a range of different depths and resolution. The choice should be determined by the type of original and the final output form. • Convert from existing digital media— e.g., photoCD. The attribute is determined by the original image. • Synthesize an image from numerical data. SYSTEM INDEPENDENT FORMATS GIF(GIF87a,GIF89a): • Graphics Interchange Format (GIF) devised by the UNISYS Corp. and CompuServe, initially for transmitting graphical images over phone lines via modems. • Uses the Lempel‐Ziv Welch algorithm (compression). • Supports only 8‐bit (256) color images. • Supports interlacing GIF89a supports simple animation JPEG: • A standard for photographic image compression created by the Joint Photographic Experts Group • Takes advantage of limitations in the human vision system to achieve high rates of compression • Lossy compression which allows user to set the desired level of quality/compression SYSTEM INDEPENDENT FORMATS TIFF: • Developed by the Aldus Corp. in the 1980's and later supported by the Microsoft • Tagged Image File Format (TIFF), stores many different types of images • (e.g., monochrome, greyscale, 8‐bit & 24‐bit RGB, etc.) • TIFF is a lossless format (when not utilizing the new JPEG tag which allows for JPEG compression) • It does not provide any major advantages over JPEG and is not as user‐controllable. • It appears to be declining in popularity Graphics Animation Files: • FLC ‐‐ main animation or moving picture file format, originally created by Animation Pro • FLI ‐‐ similar to FLC • GL ‐‐ better quality moving pictures, usually large file sizes Postscript/ PDF: • A typesetting language which includes text as well as vector/structured graphics and bit‐mapped images • Used in several popular graphics programs (Illustrator, FreeHand) • Does not provide compression, files are often large SYSTEM DEPENDENT FORMATS Windows(BMP): • A system standard graphics file format for Microsoft Windows • Used in PC Paintbrush and other programs • It is capable of storing 24‐bit bitmap images Macintosh(PAINT, PICT): • PAINT was originally used in MacPaint program, initially only for 1‐bit monochrome images. • PICT format is used in MacDraw (a vector based drawing program) for storing structured graphics X‐windows(XBM): • Primary graphics format for the X Window system • Supports 24‐bit color bitmap • Many public domain graphic editors, e.g., xv • Used in X Windows for storing icons, pixmaps, backdrops, etc. PNG: THE FUTURE OF GIF • The Portable Network Graphics (PNG) format was designed to replace the older and simpler GIF format and, to some extent, the much more complex TIFF format. • Advantages over GIF: • Alpha channels (variable transparency) • Also known as a mask channel, it is simply , p y a way to associate variable transparency with an image. • Gamma correction (cross‐platform control of image brightness) • Two‐dimensional interlacing (a method of progressive display) GIF uses 1‐D interlacing. • Better Compression (5‐25% better) • Features: • Supports three main image types: true color, grayscale and palette‐based (``8‐bit''). JPEG only supports the first two; GIF only the third. • Shortcomings: • No Animation BITMAPPED IMAGES • A bitmapped image is stored as a sequence of pixels at some particular resolution. • Common bitmapped images include: • Desktop icons • Scanned images • Photographs • Formats include: • JPEG (compressed image) • PNG, BMP INDEXED COLOR • Indexed color is a way of compressing an image so it uses less memory. • Each pixel in the image is a replaced by an entry (index) to a color palette. • If the index is 8 bits, then the palette can store 256 different colors. • Each color in the palette is still stored using 24 bits. • This reduces overall storage by approximately 66% • Lets see an example; • Each 24 bit pixel in the original image is replaced by an 8 bit index, specifying the position of the color in the palette. • The image memory size has been reduced, but with the limitation of only allowing 256 different colors. WEB SAFE COLOR PALETTE • Indexed color was common on early computers and various manufacturers devised their own standard color palettes. • Microsoft devised a palette which mixed 216 normal colors with 40 special codes for certain windowing purposes. • This palette was used as the basis of the Web Safe Color Palette • This defines 216 colors that will accurately y display on any computer and so can be safely transferred across the World Wide Web. POSTERIZATION • If an image has more than 256 (or 216) colors then there’s an obvious problem with converting it to indexed color. • It is necessary to find all the pixels which are similar in color and map them to one entry in the color palette. • This may cause areas of textured color to be replaced by crude blocks of a single color. • This effect is called Posterization (since advertising posters often use this technique deliberately). DITHERING • Dithering is a technique which reduces the visual impact of posterization. • Single color areas are sprinkled with darker (or lighter) colored pixels. • All the colors used are chosen from the color palette (of course). • Often dithering is not noticeable, but sometimes it introduces a grainy effect into the image. LINE ANTI‐ALIASING • A straight line which is not horizontal or vertical can look jagged due to the rectangular layout of pixels. • Anti‐aliasing is a similar concept to dithering. • When enlarged, the anti‐aliasing is very obvious. However, when viewed at normal size, the grey shading produces the illusion of straight lines. BITMAP EDITING PROGRAMS • There are numerous programs for editing bitmapped graphics: • – Photo Shop • – Paint Shop • – Fireworks • These programs usually save files in a number of file formats: • BMP Windows bit map • GIF Graphics Interchange Format • PNG Portable Network Graphic Typical Editing Features • Most bitmap editors offer these features: • File opening, closing, saving commands. • Resizing, cropping commands • Selection tools: • Rectangle, lasso, magic wand. • Brightness, contrast, colour adjustment. • Brush and pencil tools. • Text tools: • Adding text captions. • Colour selection tools: • Palette selection, draw bars, eye dropper. • Filtering tools: • Sharpening, blurring..
Load more

Recommended publications
  • Color Models
    Color Models Jian Huang CS456 Main Color Spaces • CIE XYZ, xyY • RGB, CMYK • HSV (Munsell, HSL, IHS) • Lab, UVW, YUV, YCrCb, Luv, Differences in Color Spaces • What is the use? For display, editing, computation, compression, …? • Several key (very often conflicting) features may be sought after: – Additive (RGB) or subtractive (CMYK) – Separation of luminance and chromaticity – Equal distance between colors are equally perceivable CIE Standard • CIE: International Commission on Illumination (Comission Internationale de l’Eclairage). • Human perception based standard (1931), established with color matching experiment • Standard observer: a composite of a group of 15 to 20 people CIE Experiment CIE Experiment Result • Three pure light source: R = 700 nm, G = 546 nm, B = 436 nm. CIE Color Space • 3 hypothetical light sources, X, Y, and Z, which yield positive matching curves • Y: roughly corresponds to luminous efficiency characteristic of human eye CIE Color Space CIE xyY Space • Irregular 3D volume shape is difficult to understand • Chromaticity diagram (the same color of the varying intensity, Y, should all end up at the same point) Color Gamut • The range of color representation of a display device RGB (monitors) • The de facto standard The RGB Cube • RGB color space is perceptually non-linear • RGB space is a subset of the colors human can perceive • Con: what is ‘bloody red’ in RGB? CMY(K): printing • Cyan, Magenta, Yellow (Black) – CMY(K) • A subtractive color model dye color absorbs reflects cyan red blue and green magenta green blue and red yellow blue red and green black all none RGB and CMY • Converting between RGB and CMY RGB and CMY HSV • This color model is based on polar coordinates, not Cartesian coordinates.
    [Show full text]
  • Indexed Color
    Indexed Color A browser may support only a certain number of specific colors, creating a palette from which to choose Figure 3.11 The Netscape color palette 1 QUIZ How many bits are needed to represent this palette? Show your work. 2 How to digitize a picture • Sample it → Represent it as a collection of individual dots called pixels • Quantize it → Represent each pixel as one of 224 possible colors (TrueColor) Resolution = The # of pixels used to represent a picture 3 Digitized Images and Graphics Whole picture Figure 3.12 A digitized picture composed of many individual pixels 4 Digitized Images and Graphics Magnified portion of the picture See the pixels? Hands-on: paste the high-res image from the previous slide in Paint, then choose ZOOM = 800 Figure 3.12 A digitized picture composed of many individual pixels 5 QUIZ: Images A low-res image has 200 rows and 300 columns of pixels. • What is the resolution? • If the pixels are represented in True-Color, what is the size of the file? • Same question in High-Color 6 Two types of image formats • Raster Graphics = Storage on a pixel-by-pixel basis • Vector Graphics = Storage in vector (i.e. mathematical) form 7 Raster Graphics GIF format • Each image is made up of only 256 colors (indexed color – similar to palette!) • But they can be a different 256 for each image! • Supports animation! Example • Optimal for line art PNG format (“ping” = Portable Network Graphics) Like GIF but achieves greater compression with wider range of color depth No animations 8 Bitmap format Contains the pixel color
    [Show full text]
  • Compression for Great Video and Audio Master Tips and Common Sense
    Compression for Great Video and Audio Master Tips and Common Sense 01_K81213_PRELIMS.indd i 10/24/2009 1:26:18 PM 01_K81213_PRELIMS.indd ii 10/24/2009 1:26:19 PM Compression for Great Video and Audio Master Tips and Common Sense Ben Waggoner AMSTERDAM • BOSTON • HEIDELBERG • LONDON NEW YORK • OXFORD • PARIS • SAN DIEGO SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Focal Press is an imprint of Elsevier 01_K81213_PRELIMS.indd iii 10/24/2009 1:26:19 PM Focal Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA Linacre House, Jordan Hill, Oxford OX2 8DP, UK © 2010 Elsevier Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions . This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this fi eld are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein.
    [Show full text]
  • MAC Basics, Terminology, File Formats, Color Models
    MAC Basics, Terminology, File Formats, Color Models Mac Short Cuts: command + c = Copy command + v = Paste command + i = Get Info (le version, date, manufacturer, etc.) option + drag = Copy folders and items on the same “drive” command + option + esc = Force quit (forces application to quit) also Finder > Apple > Force Quit space bar = in Finder Window gives you a quick look at les (without opening the le) Mac Operating System: Additional information on Mac OSX http://www.apple.com/ndouthow/mac/#tutorial=anatomy (video introduction to OS) Terminology: Bit- The smallest unit in computing. It can have a value of 1 or 0. Byte - A (still small) unit of information made up of 8 bits. Kilobyte (KB) - A unit of approximately 1000 bytes (1024 to be exact). Most download sites use kilobytes when they give le sizes. Megabyte (MB) - A unit of approximately one million bytes (1,024 KB). Gigabyte (GB) - Approximately 1 billion bytes (1024 MB). Most hard drive sizes are listed in gigabytes. Context: • 3 1/2" floppy drive holds 1.44 Megabytes (1,474 KB). [NOW OBSOLETE] • CD Rom holds up to 700 Megabytes (around 450 3.5 floppies). • 20 Gig hard drive will hold the same amount of info as 31 CD ROMs or 14,222 of the 3.5 floppy disks. • a typical page of text is around 4KB. File Formats: Graphics le formats dier in the way they represent image data (as pixels or vectors), in compression techniques, and which Photoshop features they support. With a few exceptions (for instance Large Document Format (PSB), Photoshop Raw, and TIFF), most file formats (withing Photoshop) cannot support documents larger than 2 GB.
    [Show full text]
  • Creating Pseudocolored Images in Photoshop
    If you would like, instead, to color these images in Photoshop, and Creating Pseudocolored Images in Downloaded from to make changes to the pseudocolor (and to the image itself), you can Photoshop do so by following these steps: Jerry Sedgewick 1. Make the grayscale image Indexed Color. Under Image on University of Minnesota the menu, choose Mocfe then Indexed Color. Indexed colored images [email protected] contain 256 grayscale or color values, as many as contained in an https://www.cambridge.org/core The method for creating pseudocolor in Photoshop can be done 8-bit image. in few steps, but the image will not be colored in the conventional way. This assumes that the image Is grayscale. If the image is in color, The conventional means for producing pseudocolor comes by using then change the image to grayscale first. For variously colored images, a look up table (LUT). This LUT is an overlay for making a range of such as those collected on a brightfield microscope, simply change the colors according to choices provided by the software. The colors are image to RGB: under Image on the menu, choose Mode then RGB matched to levels of brightness and darkness in the image (grayscale Color. In this scenario, the green channel is chosen as the grayscale pixel values), typically from a short to long wavelengths. In that sce- image, this most matches what we see by eye. nario, violet colors are matched to the black and near-black pixels and If the image contains shades of one color only (such as fluores- red to those dose to absolute white.
    [Show full text]
  • Color in PDF/A-1
    PDF/A Competence Center TechNote 0002: Color in PDF/A-1 The PDF/A-1 requirements related to color handling may be confusing to users and developers who are not familiar with color management concepts and ICC profiles. This TechNote describes the affected objects in PDF, details the require- ments of PDF/A-1 with respect to color handling, and provides recommenda- tions for color strategies in common situations. Contrary to popular belief, specifying an RGB value for, say, black does not accu- rately specify any color, but merely instructs a particular device to render the darkest possible color – which will be different on different devices. Similarly, 50% red in RGB may look like a clearly specified color, but it fails to define the red base color to use. Again, the visual results will be different on multiple out- put devices. These problems can be solved by using device-independent color specifications. Since PDF/A-1 is targeted at long-time preservation of the document’s visual appearance, device-independent color specification methods are required. PDF/A-1 makes use of several PDF concepts for specifying color without any de- pendency on actual output devices. 2008-03-14 page 1 PDF/A Competence Center 1 PDF Color Concepts 1.1 Color Spaces in PDF PDF supports various color spaces which can be grouped as follows: • Device color spaces refer to a specific output technology, and cannot be used to specify color values such that colors are reproducible in a predictable way across a range of output devices: DeviceGray, DeviceRGB, DeviceCMYK.
    [Show full text]
  • Graphics File Formats Reference - Webopedia.Com Page 1 of 5
    Graphics File Formats Reference - Webopedia.com Page 1 of 5 Enter a term... Term of the Day Recent Terms Did You Know? Quick Reference All Categories Home > Quick Reference > Graphics File Formats Graphics File Formats Related Terms graphics file formats » Tweet 0 Data Formats: File Formats and T Extensions » By: Vangie Beal server (Spo Posted: 05-13-2005 , Last Updated: 06-24-2010 Data Formats and Their File Exte A Quick Reference S » Data Formats and Their File Exte T » Data Formats and Their File Exte A » format » Data Formats and Their File Exte G » Data Formats and Their File Exte R » Data Formats and Their File Exte I » Data Formats and Their File Exte P » Data Formats and Their File Exte V » Data Formats and Their File Exte J » Data Formats and Their File Exte C » Graphics (n.) Refers to any computer device or program that makes a computer capable of displaying and manipulating pictures. T also refers to the images themselves. http://www.webopedia.com/quick_ref/graphics_formats.asp 20/09/2011 Graphics File Formats Reference - Webopedia.com Page 2 of 5 File Format A format for encoding information in a file. Each different type of file has a different file format. The file format specifies fir whether the file is a binary or ASCII file, and second, how the information is organized. Common Graphic & Image File Formats Some of the most used and common graphics formats used today ate TIFF, JPEG, and GIF. The Tagged Image File For (TIFF) is widely used in business, offices, and commercial printing environments.
    [Show full text]
  • Computer Labs: the BMP File Format
    Computer Labs: The BMP file format 2o MIEIC Pedro F. Souto ([email protected]) November 26, 2018 Digital Image File Formats XPM as we have defined has some limitations I Good only for indexed modes I It is not standard I Need to manually edit the XPMs bmp has been used by many LCOM projects in recent years I It is relatively simple, and you can use some libraries available on the Web to load bmp files I It is supported by some well know graphics editors, e.g. GIMP Example: Using C Arrays to Store XPMs static char *pic1[] = { "32 13 4", /* number of columns and rows, in pixels, and colors */ ". 0", /* ’.’ denotes color value 0 */ "x 2", /* ’x’ denotes color value 2 */ "o 14", /* .. and so on */ "+ 4", "................................", /* the map */ "..............xxx...............", "............xxxxxxx.............", ".........xxxxxx+xxxxxx..........", "......xxxxxxx+++++xxxxxxx.......", "....xxxxxxx+++++++++xxxxxxx.....", "....xxxxxxx+++++++++xxxxxxx.....", "......xxxxxxx+++++xxxxxxx.......", ".........xxxxxx+xxxxxx..........", "..........ooxxxxxxxoo...........", ".......ooo...........ooo........", ".....ooo...............ooo......", "...ooo...................ooo...." }; Question How many elements does an XPM array have? The BMP File Structure Bitmap File Header File metadata: Bitmap Info Header/DIB Header Pixmap and pixel format metadata I There are several versions, the most recent one is v5 Color Table/RGB Quad Array i.e. color palette I Used mainly for indexed color representations Pixel Array the pixmap Other structures with extra information or for padding are optional. Image with the BMP file fomat , via Wikipedia Bitmap File Header typedef struct tagBITMAPFILEHEADER { WORD bfType; // this is 2 bytes DWORD bfSize; // this is 4 bytes WORD bfReserved1; WORD bfReserved2; DWORD bfOffBits; }; Type Must be ’B”M’, in ASCII I But there other format versions Size Size of file OffBits Pixmap array offset (in file) Bitmap Info Header I Contains metadata about: Pixmap e.g.
    [Show full text]
  • Digital Image Technology
    Digital Image Technology Digital Image Technology Seminar Notes Douglas Dixon Manifest Technology® LLC May 2005 www.manifest-tech.com 5/2005 Copyright 2004-2005 Douglas Dixon, All Rights Reserved - www.manifest-tech.com Page 1 Digital Image Technology Digital Images • Image Characteristics – Image Types: Vector / raster, Graphics / photos, Animation – Resolution: Display, photos, scanners/ printers; DPI – Color Depth: Monochrome, gray, indexed, full; Color spaces • Image Compression – Image File Formats – Web, Photos, Print • Image / Photo Processing – Scanning, Printing – Image Editing and Enhancement 5/2005 Copyright 2004-2005 Douglas Dixon, All Rights Reserved - www.manifest-tech.com Page 2 1 Digital Image Technology Image Types • Vector / object / line art – PowerPoint, Adobe Illustrator – Graphics shapes, type, styles / attributes – Logos, for print, scale-independent • Graphics / drawings / logos – MS Paint – limited colors, flat – GIF files • Full-color / photos / continuous-tone – Grayscale and color – Adobe Photoshop – Scanned, digital photos, painting effects • Animations – Animated GIF – flip-book – Flash – scripted, programmed 5/2005 Copyright 2004-2005 Douglas Dixon, All Rights Reserved - www.manifest-tech.com Page 3 Digital Image Technology Image Resolutions • Resolution Handheld / 160 – Pixels – width x height phone 320 – Video – dots x lines PC display VGA 640 x 480 – PC – Display Properties XGA 1024 x 768 / 800 SXGA 1280 x 1024 • Capture UXGA 1600 x 1200 – Sampled – Sample rate Television NTSC 720 x 480 – Camera lens and imager High Def 720p 1280 X 720 – Scanner 1080i 1920 X 1080 Digital Cam 1 mpix ~ 1024 x 1024 • View: Perceived Resolution 2 mpix ~ 2048 x 1024 – Display size 5 mpix ~ 2500 x 1900 – Pixel size/structure 7 mpix ~ 3000 x 2400 – Viewing distance 8 mpix ~ 3264 x 2448 • Aspect Ratio 5/2005 Copyright 2004-2005 Douglas Dixon, All Rights Reserved - www.manifest-tech.com Page 4 2 Digital Image Technology Sampling: DPI vs Resolution • Scanner – Sampling rate – DPI – Dots Per Inch – 4800 x 2400, 600 x 1200, optical res vs.
    [Show full text]
  • Color, Graphics and Hardware Monitors and Display
    Color, graphics and hardware Monitors and Display •No two monitors display the same image in exactly the same way 1. Gamma settings - hardware setting on a monitor that controls the brightness of the pixels that display. • MAC displays lighter, PC displays a bit darker • You can “correct” for gamma settings by lightening or darkening images. 2. Color Calibration on different monitors • Everyone’s monitor will display differently • particularly if monitor has been calibrated for a special purpose. • There is no consistent color calibration that you can count on! 3. Different Display Technology: • CRT (Cathode Ray Tube) • LCD (Liquid Crystal Dislpay) • Plasma • They use different technologies and will display differently; some differences are subtle, others are not. 4. Monitor Resolution Settings: • people choose the size of the pixel they want to display. • The higher the resolution, the smaller the pixel. • Images “look” bigger on lower settings than on higher settings. Common settings are (4:3 ratio): 640 x 480, 800 x 600, 1024 x 768 • Laptops generally have a different aspect ratio for their display than traditional CRT monitors. • Be very careful when designing sites that your pages aren’t too wide for other displays. Image File Formats - standardized way to organize and store information - image files composed of either pixel or vector - vector (geometric): rasterized for display - pixel: grid, numbers for brightness, color, etc Image File Size - dimensions of image: pixels X pixels ( in X in ) - image resolution: amount of pixels
    [Show full text]
  • Comparison of LSB Steganography in GIF and BMP Images
    International Journal of Soft Computing and Engineering (IJSCE) ISSN: 2231-2307, Volume-3, Issue-4, September 2013 Comparison of LSB Steganography in GIF and BMP Images Eltyeb E.Abed Elgabar, Haysam A. Ali Alamin Abstract- Data encryption is not the only safe way to protect A. Basic terms data from penetration given the tremendous development in the • Cover-object, c: the original object where the message information age particularly in the field of speed of the processors has to be embedded. Cover-text, cover-image,... and the cryptanalysis. In some cases, we need new technologies or • Message, m: the message that has to be embedded in the methods to protect our secret data. There has emerged a set of new cover-object. It is also called stego-message or in the technologies that provides protection with or without data encryption technology such as data hiding. The word watermarking context mark or watermark. steganography literally means ‘covered writing’. It is derived from • Stego-object, s: The cover object, once the message has the Greek words “stegos” meaning “cover”, and “grafia” been embedded. meaning “writing”. Steganography functions to hide a secret • Stego-key, k: The secret shared between A and B to message embedded in media such as text, image, audio and video. embed and retrieve the message There are a lot of algorithms used in the field of information hiding in the media; the simplest and best known technique is B. The steganographic process Least Significant Bit (LSB). • Embedding function, E: is a function that maps the In this paper we have made a comparison and of the (LSB) tripled cover-object c, message m and stego-key k to a algorithm using the cover object as an image.
    [Show full text]
  • Using Colorways
    WHITE PAPER | ONYX 11 Textile Using ColorWays onyxgfx.com Introduction Colorways is a new tool for ONYX 11 and Thrive 11 Textile editions. Colorways is part of the Patterns tools in Job Editor. This tool makes it easy to replace the colors in a pattern. The set of replaced colors (colorways) can be applied to other jobs or automated using a Quick Set. Colorways supports specific file formats, indexed color TIFF, separation TIFF and multichannel PSD. This document will explain the basics of each file type and using them in Colorways. Colorways and Digital Printing Important Terms and Definitions Colorway: An Industry term that refers to a set of colors used in a pattern. Lab (L*a*b*): A device independent color space that includes all human perceivable colors. An example of a colorway is camouflage. The pattern is identical, but the colorways differ based on the type of environment. In ONYX Colorways, a single image file is used and the print operator applies a colorway based on the desired output. Designing Files for Colorways There are many design applications that can create files that are supported in Colorways. This document will use Adobe Photoshop to describe how to create each file type. Description of Indexed Color Indexed Color is a color mode used in textile work. Indexed Color produces images with a limited number of colors. It was designed to conserve file size while preserving the visual quality of the original image. File size reduction is accomplished by limiting the Figure 1: Indexed Color options in Adobe Photoshop number of colors and storing them in a color lookup table (CLUT).
    [Show full text]