Multimedia Technology
Chapter 3: Image File Formats
This chapter discusses various Image file formats, JPG, GIF, PNG, TIF, Difference between JPG vs GIF vs PNG.
Lecture Contents:
- Graphical Raster Devices
- Popular file Formats
- Graphical Image File Format (GIFF)
- JPEG / JPG
- JPEG vs GIF
- Portable Graphics Network (PNG)
- Comparision between JPG vs. PNG
- Tagged Image file Format (TIFF)
- Exchange Image File (EXIF)
- System Dependent File 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.
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.
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.
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.
PNG
PNG stands for Portable Network Graphics (PNG). The PNG format is intended as a replacement for GIF in the WWW and in image editing.
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.
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.
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
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).
Chapter 3_ Images File Formats
(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
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).
Chapter 3_ Images File Formats
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