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INTRODUCTION
This project can be used to compress a bitmap file and after compression the bitmap file will change into the RLE file format. Then, the RLE file can again be decompress to get the previous original bitmap file. Thus, the bitmap file can make simpler to stored and manipulate (i.e. edit, change, transferring, etc.). Finally, by using some concept from this algorithm, not only the bitmap file, other file format can also be made into the compressions formats.
UNDERSTANDING IMAGES
An image is composed of array of small squares, called pixels, arranged in rows and columns. Each pixel has a specific color value and location. They can be called as array of values, were value is a collection of numbers describing the attributes of a pixel in the image (in bitmaps, for example, the values are single binary digits). Often these numbers are fixed point representation of a range of real numbers; for example, integers through 0 to 255 often used to represent the number from 0.0 to 1.0. Often, too these numbers represent the intensity at a point in the image or he intensity of one color component at that point. The dimensions o the array are called the width and height of the image, and the number of its associated with each pixel in the array is called depth.
BASIC IMAGE FORMATS
1. RASTER FORMAT: A Raster format breaks an image into a grid of equally sized pieces, called pixels, and records color information for each pixel. On increasing the magnification the pixels are visible as squares on the screen. A Raster program creates objects by grouping pixels. An object is stored as a group of pixels with information about each pixel color. Pixels can be blended to create soft edges and smooth transitions between objects. This makes the format a good choice to use for saving photographs.
An image in the Raster Format is resolution-dependent. We can specify the resolution and pixel dimensions when we create the image. If we late decide to increase its size, we enlarge each pixel, which lowers the image quality.
2. VECTOR FORMAT: A Vector image is composed of mathematical instructions for drawing the image. Each object is stored as a separate item with information about its relative position in the image; it’s starting and ending points, width, color, and curve information. This makes them suitable for logos, fonts and line drawings.
An image in the Vector Format is resolution-independent. It can be resized without losing details because it is stored as a set of instructions, not a collection of pixels. Each time you display an image, you recreate it. Vector files are comparatively smaller too. But vector cannot reproduce photo realistic images accurately.
MAJOR IMAGE FILE FORMATS
1. BMP: It is the windows standard for bitmap files. It is the most widely used format. A set of bits or bytes specifies the intensity of a pixel. It stores information through which the computer can recreate the picture on the screen.
We use the BMP format for windows wallpaper and other system graphics.
2. GIF: GIF (Graphics Interchange Format), it is a commonly used image format for Internet graphics. It limits the number of colors used in an image to a maximum of 256, thus reducing its color depth. As an image being converted to the *.GIF, all the colors within the image would be forced to best match the 256 index colors pre-determined by your computer’s operating system. This format is most suitable for images with few solid colors such as icons but is less suitable for photo-realistic images due to its limitation colors.
3. JPEG: JPG or JPEG (Joint Photographic Experts Group) file format is another commonly used image format for Internet graphics and for sending pictures as attachments via e-mail.
This file format is suitable for displaying photo-realistic images because it does not limit the number of colors used in any given image.
4. TIFF: TIFF (Tagged Image File Format) is a vector type file format in which image maintains its quality even when it is enlarged. It is one of the toughest to decode. An IFD (Image File Directory) in a TIFF is a table that identifies one or more variable-length chunks of data called tags, which hold information about the image. Its tags wholly define an image encoded in TIFF file, and the file format is highly extensible because additional features can be added simply by defining additional tag types.
SECTION # 2
IMPORTANCE OF BITMAP
* GUI-ONE OF THE MOST AMAZING THINGS IN A SWITCH FROM DOS TO WINDOWS.
When operating systems like windows were developed the most visible advantage was a user interface a noble man once said
“A picture is worth a thousand words” This was proved with the advent of UI. No longer had one had to remember long path names and users could live without the fear of mistyping the names of directories and then retype them again. The process of many system operations such as downloading a file may also be displayed graphically. The need for remembering hundreds of commands was extinct. Folder/File icons replaced typing paths and mouse substituted keyboard to certain extent. These fancy buttons and mouse pointers would have to make of lines. One of the most important things in creating a user-friendly interface is the use of bitmaps.
* MOTHER OF ALL IMAGE FILE FORMATS.
Bitmaps being the oldest can be rightly called the mother of all image formats. This is because all other image file formats are one or the other compressed forms of bitmaps only. It is the simplest to store and manipulate. It is wise to store uncompressed large bitmaps into compressed smaller forms and thus other file formats like GIF<JPG<ETC. were developed but the core of all of them is
bitmap because while displaying these files must be decoded to the form of bitmaps as it most closely resembles the way images are displayed on screen and stored in video memory.
WHAT IS BITMAP?
The term bitmap is throwbacks from when monitors could only display one other color besides black for two colors data files that store an image, each bit in data file represent one pixel: a 1 meant the pixel was on, a 0 meant the pixel was off.
A bitmap file stores the information a computer needs to recreate a picture. You and I see an image on the screen as a beautiful sunset, but the compute sees it as ones and zero’s it’s what the computer does with those one’s and zeros that enables it to reproduce the original image. Ultimately the bits and bytes in the bitmap tell the computer what color to paint each pixel in the image.
A bitmap representation stores the graphic/image data in the same manner that the compute monitor contents are stored in video memory. A monitor screen image is composed of small points, termed pixels. The numbers of pixels that compose a monitor image determine the quality of the image. The more the pixel, the higher the resolution.
The BMP file format is the native bitmap file format for windows native because it closely matches the format in which windows stores bitmaps internally.
This file format can be store uncompressed so reading BMP.
Files are fairly simple: most other graphics formats are compressed and some like GIF are difficult to decompress.
The term bitmap strictly speaking applies to only 1-bpp bi level systems for multiple bpp systems we use a more general term pixmap or pixel map.
Window bitmap files are stored in a device independent bitmap (DIB) format that allows windows to display bitmap on any type of display device. The term “device independent” means the bitmap specifies pixel color in a form independent of the method used by a display to represent color. The default filename extension of a windows DIB file is .BMP