MULTIMEDIA TECHNOLOGY

IMAGE FILE FORMATS

Dr. Zeeshan Bhatti

BSIT-IIIChapter 3

BY: DR. ZEESHAN BHATTI 1

GRAPHICAL RASTER DEVICES•Raster displays and scanners

•Ink-jet, laser, electrostatic plotters, fax machines

BY: DR. ZEESHAN BHATTI 2

POPULAR FILE FORMATS

BY: DR. ZEESHAN BHATTI 3

GIF (GIF87A, GIF89A)

Graphics Interchange Format (GIF) devised by the UNISYS Corp. And Compuserve, initially for transmitting graphical images over phone lines via modems.

GIF standard is limited to only 8-bit (256) colour images, suitable for images with few distinctive colours (e.g., graphics drawing)

One byte per pixel

GIF reduces colors to 256 (256 from 224 colors)

Uses a colour map of 256 possible RGB values, contained in file. Only the 8 bit index is transmitted for each pixel that contains the closest match color to the original one.

Supports interlacing. - successive display of pixels in widely-spaced rows by a 4-pass display process.

BY: DR. ZEESHAN BHATTI 4

GIF (GIF87A, GIF89A)

GIF actually comes in two flavours:

1. GIF87a: The original speciation.

2. GIF89a: The later version. Supports simple animation via a Graphics Control Extension block in the data, provides simple control over delay time, a transparency index, etc.

Compression ratio is close to 3:1. Color table is transferred to the receiver.

Provides support for animation - multiple pictures per file.

Provides one dimensional interlacing dividing the image into 4 groups: first contains 1/8 of the image, second –1/8, third – ¼, last – 1/2.

This is patented technologyBY: DR. ZEESHAN BHATTI 5

JPEG / JPG

•JPEG: The most important current standard for image compression.

A standard for photographic image compression created by the Joint Photographics Experts Group

• Takes advantage of limitations in the human vision system to achieve high rates of compression.

•JPEG allows the user to set a desired level of quality, or compression ratio (input divided by output).

• Lossy compression which allows user to set the desired level of quality/ compression.

BY: DR. ZEESHAN BHATTI 6

As an example, Fig. shows our forestre. image, with a quality factor Q=10%.

This image is a mere 1.5% of the original size.

JPEG image with low quality specied by user.BY: DR. ZEESHAN BHATTI 7

BY: DR. ZEESHAN BHATTI 8

PNGPortable Network Graphics (PNG)

The PNG format is intended as a replacement for GIF in the WWW and in image editting.

GIF uses LZW compression, which is patented by Unisys. All uses of GIF may have to pay royalties to Unisys - PNG contains no patented technology.

PNG uses unpatented zip technology for compression

Provides transparency using alpha value.

2 Dimensional interlacing.

BY: DR. ZEESHAN BHATTI 9

Support for up to 48 bits of color information | a large increase.

Files may contain gamma-correction information for correct display of color images, as well as alpha-channel information for such uses as control of transparency

Figure: PNG of a single toucan overlaid to create a single picture. Notice how the shadows are overlaid on lower toucan.

PNG supports multiple image layers, and adds an alpha byte to the RGB bytes to describe how to combine each pixel with pixels from other layers or other images, ranging from totally transparent to totally opaque.

BY: DR. ZEESHAN BHATTI 10

COMPARISION BETWEEN JPG VS PNG

BY: DR. ZEESHAN BHATTI 11

BY: DR. ZEESHAN BHATTI 12

BY: DR. ZEESHAN BHATTI 13

BY: DR. ZEESHAN BHATTI 14

TIFF

• Tagged Image File Format (TIFF), stores many different types of images

(e.g., monochrome, greyscale, 8-bit & 24-bit RGB, etc.) –> tagged

• The support for attachment of additional information (referred to as \tags") provides a great deal of flexibility.

• Developed by the Aldus Corp. in the 1980’s and later supported by the Microsoft

The most important tag is a format signifier: what type of compression etc. is in use in the stored image.

• TIFF is a lossless format (but now a new JPEG tag allows one to opt 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

BY: DR. ZEESHAN BHATTI 15

EXIF ( NOW NEF)

(Exchang Image File) is an image format for digital cameras:

1. Compressed EXIF _les use the baseline JPEG format.

2. A variety of tags (many more than in TIFF) are available to facilitate higher quality printing, since information about the camera and picture-taking conditions (flash, exposure, light source, white balance, type of scene, etc.) can be stored and used by printers for possible color correction algorithms.

3. The EXIF standard also includes specification of file format for audio that accompanies digital images. As well, it also supports tags for information needed for conversion to FlashPix (initially developed by Kodak).

BY: DR. ZEESHAN BHATTI 16

SYSTEM DEPENDENT FORMATS Many graphical/imaging applications create their own file format particular to the systems they are executed upon. The following are a few popular system dependent formats.

Microsoft Windows: BMP

Macintosh: PAINT and PICT

X-windows: XBM

PSD

BY: DR. ZEESHAN BHATTI 17

Microsoft 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 and 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

 BY: DR. ZEESHAN BHATTI 18

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

BY: DR. ZEESHAN BHATTI 19

POSTSCRIPT/ENCAPSULATED POSTSCRIPT Postscript is an important language for typesetting, and many high-end printers have a Postscript interpreter built into them.

• A typesetting language which includes text as well a vector/structured graphics and bit-mapped images

• Postscript is a vector-based picture language, rather than pixel-based: page element definitions are essentially in terms of vectors.

• Used in several popular graphics programs (Illustrator, FreeHand)

• Does not provide compression, files are often large

• Encapsulated Postscript les add some additional information for inclusion of Postscript les in another document.

BY: DR. ZEESHAN BHATTI 20

THANKYOU

Q & A

BY: DR. ZEESHAN BHATTI 21

For My Slides and Handoutshttp://zeeshanacademy.blogspot.com/https://www.facebook.com/drzeeshanacademy