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Java Example

Object-Oriented Design Similar object classes Common interfaces Common usage Code reuse-- inheritance Defers implementation and algorithm decisions. Procedural Design Algorithm centered-- forces early implementation and algorithm decisions Exposes more details Difficult to extend

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Java Example

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  1. Object-Oriented Design • Similar object classes • Common interfaces • Common usage • Code reuse-- inheritance • Defers implementationand algorithm decisions • Procedural Design • Algorithm centered-- • forces early implementationand algorithm decisions • Exposes more details • Difficult to extend • Difficult to maintain Java Example

  2. void processShape(Shape s) { s.setColor(Color.red); // ... do stuff s.draw(); } Circle c = new Circle(x, y, r); Point2D v1 = new Point2D(x1, y1); Point2D v2 = new Point2D(x2, y2); Point2D v3 = new Point2D(x3, y3); Triangle t = new Triangle(v1, v2, v3); Point2D c1 = new Point2D(u1, v1); Point2D c2 = new Point2D(u2, v2); Triangle r = new Rectangle(c1, c2); processShape(c); processShape(t); processShape(r); Polymorphism

  3. Variables in Java must be objects, arrays, or one of the primitive data types • Java has 8 primitive data types: (boolean, byte, short, int, long, double, float, char) • Notes: • All integer types are signed (and there is no unsigned keyword) • Unlike C and C++ char variables are 16 rather than 8 bits • Primitive data types are passed by value

  4. Java has 8 primitive data types boolean like6837 = true; // boolean likewise have values {true, false} byte teeth = 32; // bytes go from -128 to 127 if (!like6837) teeth = teeth - 1; float pi = 3.141592f; // you need the "f" here short classes = 0xbad; // hexadecimal

  5. Java Arrays • Java arrays fall between a primitive data type and an object • Properties of Java arrays: • can contain objects, primitive types, or other arrays • contents are accessed via zero-based positive integers enclosed within the brackets, [, and ] • declaration and creation of arrays are distinct operations • created with the new operator • uninitialized arrays have a value of null • have a single instance variable called length • checks at run time, that all accesses are between 0 and length - 1 • passed to methods by reference

  6. Java Arrays byte buffer[]; // array declaration (buffer = null) buffer = new byte[1024]; // array creation (contents initialized to zeros) int table[] = new int[10]; // declaration and creation combined int sqrs[] = {0, 1, 4, 9, 16, 25, 36, 49, 64, 81 }; // with an initializer buffer[5] = sqrs[sqrs.length-1]; // array references int triangle[][] = new int[3][]; triangle[0] = new int[3]; triangle[1] = new int[2]; triangle[2] = new int[1];

  7. Java Objects • Properties of Classes • All Java code is contained within objects • Objects are passed to methods by reference • Definition, declaration, and creation of objects are distinct • Instances of objects are created with new and have a value of null • Objects have four forms: the class, the abstract class, the inner class, and the interface

  8. Java Objects class Circle { // object definition static double pi = 3.141592; // class variable double radius; // instance variable public Circle(double r) { // constructor method radius = r; } public double circumference() { return 2*pi*radius; } public double area() { return pi*radius*radius; } } Circle c; // object declaration c = new Circle(4.0); // object creation double a = c.area();

  9. Java 2 incorporates the Java2D API ( Application Programming Interface) as part of the standard set of APIs The Java2D API consists of a number of classes, distributed amongst the old packages: java.awt and java.awt.image and six new packages:java.awt.color, java.awt.font, java.awt.geom, java.awt.print, java.awt.image.renderable and com.sun.image.codec.jpeg Packages java.awt.image Provides classes for creating and modifying images. http://java.sun.com/products/jdk/1.2/docs/api/java/awt/image/package-summary.html com.sun.image.codec.jpegProvides classes for encoding and decoding JPEG images.

  10. The BufferedImage class java.awt.image Class BufferedImage java.lang.Object | +--java.awt.Image | +--java.awt.image.BufferedImage BufferedImage class supplies functionality to do immediate mode processing of image data BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_BYTE_GRAY);

  11. The BufferedImage class • - BufferedImage is a subclass of Image, and is in the java.awt.image package • - BufferedImage objects have a Raster and a ColorModel • -Several types of image formats are provided • BufferedImage.TYPE_BYTE_GRAY - 8 bits sample per pixel • BufferedImage.TYPE_INT_RGB – 8 –bit red, green and blue samples, packed into an int . • BufferedImage.TYPE_3BYTE_BGR - 8 bits each of RGB

  12. The BufferedImage class - Methods are provided to getWidth( ), getHeight( ), and getType( ) - Access to pixels is provided through getRGB( ) and setRGB( ) these are typically inefficient for DIP purposes because they are packed and represented according to the ColorModel

  13. The BufferedImage class -The Raster object has a DataBuffer and a SampleModel - A Raster object is read-only, WriteableRaster allows you to modify image data WritableRaster raster = image.getRaster(); - allows access to samples without the overhead of the ColorModel - many variations on getPixel( ), getSample( ), setPixel( ), setSample( ) raster.setSample(x, y, band, value); -sets the sample at position x,y to value - band is 0 for grayscale images -band is 0, 1, or 2 for RBG images

  14. When placing images into online or archival storage, it is important to select an appropriate file format . Image file formats Magic Number bytes Image data header Image file formats specify some kind of information and consists of a header segment and data segment. The headers begin with a signature or “magic number” – a short sequence of bytes designed to identify the file as an image with that specific format. The header will contain also, the width and the height of the image.

  15. Image File formats can be grouped roughly into three categories : • Device-specialized formats. The structure of the image file may be chosen to facilitate rapid display on a particular type of workstation. The disadvantages of device specialized formats include their lack of portability, their inefficiency when used with other hardware.Example: ICC - Used for Kodak printer • Software-specialized formats Are those designed by a software vendor to be used with a particular program or class of programs .Examples include the PCX and Windwos bitmap (BMP) formats commonly found on PCs, or the MacPaint format used on Aplet Macintosh computers. • Interchange formats : GIF, PNG, JPEC

  16. Graphics Formats for the World Wide Webhttp://www.wdvl.com/Graphics/Formats/ • There are several kinds of graphics files:- • Raster files (also called bitmapped files) contain graphics information represented as pixels, such as photographic images. These include GIF, PNG, and JPEG. • Animation formats are usually sequences of raster data. • Vector files contain data for mathematical operations and are typically used to store line art and CAD information. • Metafiles may contain either raster or vector graphics data. • Page Description Languages (PDL) are used to describe the layout of a printed page of graphics and text, e.g. Adobe PDF. • Multi-dimensional object formats store graphics data as a collection of objects (data and the code that manipulates it) that may be rendered as if seen from any viewpoint. • Virtual Reality Modeling Language (VRML) is a 3D, object-oriented language used for describing "virtual worlds" hyperlinked within the World Wide Web. • Multimedia file formats are capable of storing any of the above types of data, often including sound and/or video information.

  17. 2D Bitmap Specifications: http://www.dcs.ed.ac.uk/home/mxr/gfx/ BIFF - Notes on the XITE 3D file format BMP - MS-Windows bitmap format BW - SGI Black & White Image File Format CGM - Computer Graphics Metafile CGM Overview & Description CGM Technical Reference (WordPerfect 5.1) CGM Information, Examples, and Source Code [Link] DRAW - Acorn's object-based vector image file format [Link] DWG - AutoCAD drawings file format information [Link] FAX - The Group 3 Facsimile standard

  18. Examples of common interchange formats are: - GIF - Graphics Interchange Format - PNG - Portable Network Graphics - JFIF - JPEG (Joint Photographic Experts Group) File Interchange Format - TIFF - Tagged Image File Format - PGM - Portable Gray Map -PBM - Portable Bit Map -PPM - Portable Pix Map - FITS - Flexible Image Transport System

  19. interchange formats - type of compression used is important lossless - no image information is lost during compression (PNG) lossy - information is lost during compression (JPEG) Generally speaking, a distinction can be made between methods that compress without loss (lossless), and thus do not eliminate any image details, and those that reduce the file size at the expense of image information (lossy). The reference photo for the versions compressed in different ways shows colorful fuchsia flowers saved in the lossless PNG format.

  20. Lossless compression methods The original image can be restored in absolutely identical form at any time – after decompression, every pixel has exactly the values it had before compression The proprietary formats of image editing programs – such as the *.PSD format in Adobe Photoshop – are often equipped with lossless compression algorithms .

  21. Lossless compression methods The so-called TIFF format (Tagged Image File Format) uses a lossless compression method known as the Lemple-Zif-Welch (LZW) method. However, this version, which good image editing programs offer as an option when saving, is only capable of significantly reducing the file size of images containing a relatively large proportion of plain-colored areas. With our photo of the fuchsia flowers, it only reduces the memory space requirement by 3 percent. Picmaster is one example of a shareware program that offers LZW compression for the TIFF format.

  22. Lossless ZIP compression method Another lossless method is ZIP compression, which can be applied to any text, program and other files, and thus also to photos. When using a standard ZIP compression program, such as PowerArchiver shareware, it reduces the file size by as much as 16 percent in the case of our fuchsia photo. However, this factor is far lower when applied to previously compressed image files.

  23. Lossy image compression methods JPEG is the image compression standard developed by the Joint Photographic Experts Group. It works best on natural images (scenes). It compresses the red-green-blue parts of a color image as three separate greyscale images - each compressed to a different extent, if desired. All the image details can be recognized precisely in the original image with a file size of 1.1 megabytes in TIFF format. So that no image information is lost, it is also available in PNG format for online comparison. The images competing with this reference photo were saved in JPEG format with 100, 80, 60, 40, 20 and 0 percent quality preservation.

  24. JPEG method In the image compressed by the JPEG method with 100 percent quality preservation, you can only see the differences compared to the reference after taking a fairly close look. Yet, this level already allows you to reduce the file size by 84 percent. The differences are still within reasonable limits if only 80 percent of the quality is preserved. However, you can see the regular structures caused by the grouping of the pixels. The additional elimination of detail information already results in hefty memory savings of 94 percent

  25. JPEG method Compression with 60 percent quality preservation makes the signs of block-by-block color equalization more obvious. In this case, the color of some of the pixel blocks does not match the surroundings. In return, this version of the image requires 95.2 percent less memory space. The first noticeable "staircases" become visible at 40 percent quality preservation. The retention of the differences in brightness is obviously no longer capable of concealing them. It is perfectly clear that saving this amount of memory space is too much of a good thing, particularly as it doesn't leave you with significantly more available memory.

  26. JPEG method If you preserve only 20 percent of the original quality, the tile-like structure of the pixel block can no longer be overlooked. In the algorithm, block formation has clearly gained the upper hand over the attempts to conceal it by preserving differences in brightness. If you totally dispense with quality preservation, the tile structure breaks up the image in a manner reminiscent of abstract painting. Now, you consistently get extreme color differences between adjacent pixel blocks.

  27. How JPEG works JPEG divides up the image into 8 by 8 pixel blocks, and then calculates the discrete cosine transform (DCT) of each block. A quantize rounds off the DCT coefficients according to the quantization matrix. This step produces the "lossy" nature of JPEG, but allows for large compression ratios. JPEG's compression techniqueuses a variable length code on these coefficients, and then writes the compressed data stream to an output file (*.jpg). For decompression, JPEG recovers the quantized DCT coefficients from the compressed data stream, takes the inverse transforms and displays the image .

  28. JPEG Tutorial Index of Hyperlinks An anonymous FTP site for more JPEG documentation is: ftp.uu.net/graphics/jpeg/ http://dynamo.ecn.purdue.edu/~ace/jpeg-tut/jpegtut1.html

  29. GIF – Special format for the Web The GIF format is a good candidate for special uses or certain images that consist of large, uniform areas of color. Although it works with the lossless LZW method, it limits the number of colors to a maximum of 256, this being equivalent to 8 bits (2 to the power of 8 equals 256) in the binary system. You should generally avoid any software that only offers a command in the style of "Save As GIF" without any further options. After all, the GIF format has numerous options and settings that you should make good use of in order to obtain optimum results.

  30. GIF format has numerous options • Interlaced: When you use this option, a GIF graphic builds up in the browser in several steps, from "coarse" to "fine". In other words: the surfer rapidly gets a rough impression of the contents of the image, which is then displayed more accurately with each pass. • Dither: Here, you can choose whether the image areas are to be displayed simply in the forms of areas of color, or whether fine dots within the areas are to simulate other shades. The dither methods often offer additional sub-options. • Palette: This option allows you to specify the makeup of the color palette of the image and how many colors it is to include. • Transparenz: This is one of the major advantages of the GIF format for use on the Internet. You can set certain colors or the entire background of an image to transparent. For instance, if you position a graphic of this kind on top of a background image or in a colored table row, these are visible outside the motif contours.

  31. GIF format Despite all the options that GIF offers, the consequence of this compression method based on reducing the number of colors is that usually substantial color falsification understandably results in halftone images, which always contain color shades. This can be seen in the following examples with 256, 128 and 64 colors. SmartSaver from Ulead converts images into these given color levels, showing you not only the result in the preview window, but also the color palette used.

  32. GIF format Reducing the number of colors to 128 intensifies the screened effect and increases the number of isolated pixels of a different color. The file size shrinks to 83 percent compared to the original image. Even further reduction to just 64 colors results in a screening effect that is reminiscent of the pop art paintings of Roy Lichtenstein. While the distortion of the colors is already very marked in comparison with the JPEG method, the memory-saving effect is only moderate, shrinking the file size by 87 percent

  33. GIF - Additional information • Unisys emphasizes on its website (http://www.unisys.com/unisys/lzw/) the fact that program manufacturers need a license to use the GIF format. • Mark Nelson has compiled interesting link (http://dogma.net/DataCompression/GIF.shtml) on the GIF format.

  34. Which compression method and when? Even before taking the photo, and also before saving the image data again on the computer, you should have a clear idea of what the images are to be used for. TIFF The TIFF format preserves all the image information during saving, making it the method of choice when large-format photos or posters are to be printed, or if you are planning on making selective enlargements, for instance because you don't have or can't use a telephoto lens when taking the shot. Lossless LZW compression is a good choice for image editing, while the ZIP format will additionally reduce the size of the file if you want to send it off in an e-mail.

  35. JPEG With the JPEG format and a powerful compression program or image editing software, you have every opportunity to compress an image for virtually any conceivable purpose. However, you always have to keep an eye on the reciprocal effect of file size and accuracy of detail. If you compress too much too soon, without retaining the original file, you will irretrievably lose the data. Which compression method and when? GIF The GIF format is ideal for compressing graphics and graphic-like images characterized by sharply defined, relatively uniform areas of color, like some comics. It is always suitable for halftone images if you want not only a high degree of compression, but also plan to integrate text into the photos or animate the images for use on the Internet. The GIF format is usually also superior to the JPEG format in terms of quality and file size when it comes to navigation buttons on websites or graphic logos.

  36. What do you compress with? One very convenient compression program is SmartSaver Pro from Ulead. It allows you to enter the exact quality level you want and check the result on the basis of a preview window.

  37. What do you compress with? Of course, the common, standard image editing programs, from Adobe Photoshop and Paint Shop Pro to Ulead PhotoImpact and MGI PhotoSuite, offer very exact setting options. When you use the "Save As…" command in Adobe Photoshop, the standard program for image editing, you can select the compression level using a slide control, a numerical scale from 1 to 10 or four levels from low to maximum.

  38. In Paint Shop Pro, the degree of compression is set in the "Save As" command either by entering a compression factor between 1 and 99 or via a slide control permitting infinitely variable adjustment between maximum and minimum quality The "Export JPEG File" command in Paint Shop Pro additionally offers a preview window for judging the image quality.

  39. Freeware and Shareware programs that use the JPEG format • ACDSee opens any JPEG file. (http://www.acdsystems.com/English/Products/ImagingProducts/ACDSee/index.htm) • IrfanView for viewing, converting and compressing.( http://irfanview.tuwien.ac.at/deutsch.htm) • XATJPEG(http://www.xat.com/jpeg_optimizer/jpeg_optimizer.shtml) Optimizer makes JPEG files particularly small and can compress certain areas of the image less than others. • Jpeg Cleaner removes supplementary information to produce even smaller files. (http://www.pppr.sk/rainbow/) • To Jpeg is for conversion to JPEG format at a click of the mouse under MacOS (http://jsam.best.vwh.net/).

  40. Interchange formats • Simple formats have a fixed size header, followed by data (PBM, PGM, PPM) • The various pieces of information needed to process an image are located at fixed offsets from the start of the file. For example , if the magic number occupies four bytes , then bytes 5-8 and 9-12 might be used to store image width and height, respectively. • 2. Tagged formats use specificcodes to tag various types of information in the file (PNG, TIFF) • Tagged formats do not require that information at fixed locations in an image file; instead they make use of special strings or codes to identify particular items of data. Example :FITS , which uses ASCII strings as tags; PNG , which uses four-byte sequences of uppercase or lowercase characters ; and TIFF, which uses numeric codes.

  41. Signature Image type Storage image P1 Binary ASCII P2 Greyscale ASCII P3 RGB ASCII P4 Binary Raw bytes P5 Greyscale Raw bytes P6 RGB Raw bytes PGM - portable graymap file format  Signature of the various PBM, PGM and PPM image format A ASCII PGM files- file's magic number is the two characters "P2". In Raw PGM files - the "magic number" is "P5" instead of "P2".  

  42. ASCII PGM -  DESCRIPTION • - A ASCII pgm file's magic number is the two characters "P2". • - White space (blanks, TABs, CRs, LFs).  • A width,formatted as ASCII characters in decimal. • - White space.  • - A height, again in ASCII decimal. • - Whitespace.  • - The maximum gray value, again in ASCII decimal. • - Whitespace. • - Width * height gray values, each in ASCII decimal, between 0 and the specified maximum value, separated by whites pace, starting at the top-left corner of the graymap, proceeding in normal English reading order. A value of 0 means black, and the maximum value means white. In an ASCII file color of each pixel is stored as a triplet of ASCII decimal values ( in the order red, green, blue)  • - Characters from a "#" to the next end-of-line are ignored (comments). • - No line should be longer than 70 characters.

  43. P2 # a simple PGM image 7 7 255 120 120 120 12 120 120 120 120 120 120 33 120 120 120 120 120 120 33 120 120 120 120 33 120 33 33 33 120 120 120 120 33 120 120 120 120 120 120 33 120 120 120 120 120 120 120 120 120 120   Here is an example of a small graymap in ASCII PGM format:

  44. There is also a variant on the format, available by setting the RAWBITS option at compile time. This variant is different in the following ways:  Raw PGM file - The "magic number" is "P5" instead of "P2".  - The gray values are stored as plain bytes, instead of ASCII decimal. - No white space is allowed in the grays section, and only a single character of whitespace (typically a newline) is allowed after the maxval. - The files are smaller and many times faster to read and write.  - Note that this raw format can only be used for maxvals less than or equal to 255. If you use the pgm library and try to write a file with a larger maxval, it will automatically fall back on the slower but more general plain format.

  45. The main advantage of the ASCII format is that pixel values can be examined or modified very easily using a standard text editor. The advantage of the raw format is that it is much more compact; in a Raw PGM file , pixel value are coded using only a single character, but in an ASCII PGM file, as many as four characters may be required for each pixel value – with the result that ASCII files consume up to four times as much space as raw files.

  46. PNG – The transparent alternative PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits. • More information on the PNG format • The W3C website contains everything you could possibly want to know about the PNG format.( http://www.w3.org/TR/REC-png.html) • Group42 champions the cause of the PNG format. (http://www.group42.com/png.htm)

  47. Indexed-color images of up to 256 colors. • Streamability: files can be read and written serially, thus allowing the file format to be used as a communications protocol for on-the-fly generation and display of images. • Progressive display: a suitably prepared image file can be displayed as it is received over a communications link, yielding a low-resolution image very quickly followed by gradual improvement of detail. • Transparency: portions of the image can be marked as transparent, creating the effect of a non-rectangular image. • Ancillary information: textual comments and other data can be stored within the image file. • Complete hardware and platform independence. • Effective, 100% lossless compression. GIF features retained in PNG include:

  48. Important new features of PNG, not available in GIF, include: • Truecolor images of up to 48 bits per pixel. • Grayscale images of up to 16 bits per pixel. • Full alpha channel (general transparency masks). • Image gamma information, which supports automatic display of images with correct brightness/contrast regardless of the machines used to originate and display the image. • Reliable, straightforward detection of file corruption. • Faster initial presentation in progressive display mode.

  49. PNG is designed to be: • Simple and portable: developers should be able to implement PNG easily. • Legally unencumbered: to the best knowledge of the PNG authors, no algorithms under legal challenge are used. (Some considerable effort has been spent to verify this.) • Well compressed: both indexed-color and truecolor images are compressed as effectively as in any other widely used lossless format, and in most cases more effectively. • Interchangeable: any standard-conforming PNG decoder must read all conforming PNG files. • Flexible: the format allows for future extensions and private add-ons, without compromising interchangeability of basic PNG. • Robust: the design supports full file integrity checking as well as simple, quick detection of common transmission errors.

  50. PNG File Structure A PNG file consists of an eight-byte signature, followed by a series of chunks. Each chunk consists of : a 32 –bit integer giving the number of bytes in the chunk’s data field; a four-byte code to indicate chunk type, zero or more data bytes; and 32 –bit cyclic redundancy check ( CRC ) for the chunk, which a PNG decoder can use to test whether the chunk data are valid. The first eight bytes of a PNG file always contain the following (decimal) values: 137 80 78 71 13 10 26 10This signature indicates that the remainder of the file contains a single PNG image, consisting of a series of chunks beginning with an IHDR chunk and ending with an IEND chunk

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