The document discusses various digital image file formats including TIFF, GIF, PNG, and JPEG. TIFF files can contain multiple images and compression methods but have large file sizes. GIF is suitable for images with few colors but loses color variation. PNG uses lossless compression and supports more colors than GIF but may have large file sizes. JPEG is used for photographs and uses lossy compression to reduce file size, but information is lost in the process. The optimal file format depends on the image type and intended use.

1. By: Sarah Ali Hasan
1st April 2013

2. A digital image is a numeric representation
of a two dimensional image.
Most software developers created a new
custom file format for each application they
develop.
Using Standardized file formats increases
the ease with which images can be
exchanged and be readable by other
software .

3. Criteria to be considered when
choosing file format:
Type of image: black & white, grayscale, scans from
documents, color images, color graphics… etc.
Storage size & compression: storage requirements &
compression method.
Capability: how important is the exchange of image
data & how important is the long-term machine
readability of the data.
Application domain.

4. Some
types of
digital
images
are
shown
next;

6. Raster Vs. Vector data:
Raster images have a finite set of digital values,
called picture elements or pixels.
Vector graphics are based on vectors (also called paths,
or strokes) which lead through locations called control
points. Each of these points has a definite position on
the x and y axes of the work plan.
Raster images contains a fixed number of rows and
columns of pixels, while vector images results from
mathematical geometry (vector) that consist of infinite
number of points having both direction and length.

7. 1-Tagged Image Format File (TIFF):
►A TIFF file can contain a number of images with
different properties .
►A TIFF specification provide a range of different
compression methods;( LZW, ZIP, CCITT & JPEG) and color
spaces which make it easy to store a number of variations
of an image in different sizes & representations together in
a single TIFF file.
►The flexibility of a TIFF has made it universal exchange
format used in archiving documents , scientific
applications, digital photography and video production.

8. Merits of TIFF format:
►The great advantage of saving files in the same TIFF
format is that no information is lost.
►Useful for transporting image files from one application
to another or from one computer to another as they are
designed to be independent of any particular hardware or
software.
► The strength of TIFF format lies in its architecture ,
which enables new image types & information blocks to be
created by defining new “tags” .

9. Demerits of TIFF format:
►TIFF files encounter errors when loading. In flexibility
also lies the weakness of this format where proprietary
tags are not always supported.
►The drawback of TIFF files is that the file size is large.
They take up a lot of space when stored and take a long
time to open in an application.
► Difficult to store. They are not useful as embedded
image files in a webpage as they take much too long to
download.

10. 2- Graphics Interchange Format (GIF) :
►Widely popular format; due to its early support for
indexed color at multiple bit depths, LZW compression,
interlaced image loading.
► Designed for color & grayscale images with maximum
8bit depth (i.e. doesn’t support true color images). GIF
files are designed to efficiently encode flat images
consisting of large areas of the same color.
►Supports color palletes in the range of (2-256); enabling
pixels to be encoded using fewer bits.

11. Merits of GIF format:
► The limited color range has the advantage that GIF
files will be smaller in size.
► Easy to store and display: When saving an image as
GIF, you can specify how the image appears as it is
downloaded. Select “Interlaced” to display the image
gradually in increasing detail as it is downloaded.
► GIF format has the ability to encode simple
animations by storing a number of images in a single
file for later sequential display. Also can be made into a
transparent image.

12. Demerits of GIF format:
► The limitation of an 8-bit palette, or 256 colors
makes the GIF format suitable for storing graphics
with relatively few colors such as simple diagrams,
shapes, logos & cartoon style images and ineffective
for detailed images or dithered images.
► Loss of color variation. GIF is not suitable
for subtle color variations retained in your image. Gif
formats are very useful for storing grey scale images
which are limited to 256 tones of grey, so that no
information is lost .

13. 3-Portable Network Graphics (PNG):
► A universal image format designed especially for
the use of the internet. PNG format was designed to
be an alternative to the GIF format .
►PNG files support 3 types of images:
1) true color (with up to 3*16 bits/pixel)
2) grayscale (with up to 16bit/pixel)
3) indexed (with up to 256 colors).
►PNG includes an alpha channel for transparency
with a maximum width of 16bit.

14. Merits of PNG format:
► Unlike GIF, the PNG format is able to retain full
16,000,000 colors. Still the format support one image
per file but it allows images of up to 2^30 * 2^30
pixels.
► The PNG format uses a lossless compression
method .
Demerits of PNG format:
► Relative large file size ensures PNG format may
be less suitable for Web or other online service.

15. 4-Joint Photographic Experts Group
(JPEG):
►It’s a standard defines a compression method used to
display continuous tone images (such as photographs)
with a goal of achieving an average data reduction of
1:16.
► The level of JPEG compression will determine how
much information is lost (this can be set in most
programs that offer jpeg compression).
► Jpeg files can be saved with the following options:
"standard", "baseline optimized" and "progressive".

16. Algorithm Core of RGB image:
1) color conversion & down sampling: color transformation from
RGB into the Y Cb Cr space is used to separate the actual color
components from the brightness Y component.

17. 2) Cosine transform & quantization in frequency
space: The image is divided up to a regular grid of 8
blocks. The frequency spectrum is computed for
each independent block using the discrete cosine
transformation. Next the spectral coefficients of each
block is quantized using quantization table; size of
this table determines the compression ratio.
3) Lossless compression: The quantized spectral
components data stream is again compressed using
lossless method (arithmetic or Huffman) in order to
remove the last redundancy in the data stream.

18. Merits of JPEG formats:
► Retains up to 16,000,000 colors.
► The ability to compress more or less to find a
compromise between file size and image quality.
Demerits of JPEG format:
► Loses information on pixel frequency values because
they may be averaged to the values of those pixels in its
immediately surroundings.
► File size larger than gif because of color information.

19. Some JPEG file formats:
*JFIF: What is normally referred to as JPEG is an instance of
“JPEG File Interchange Format”(JFIF) .It specifies a file format
based on the JPEG standard by defining the remaining
necessary elements of the file format.
*EXIF: The exchangeable image file format, Is a variant of (JFIF)
designed for storing image data originating on digital cameras.
It is the practically used file format by all manufacturers as the
standard format for storing digital images on memory cards.
*JPEG-2000: was designed to overcome some of the
weaknesses of traditional JPEG codec. Higher compression
ratios achieved here (up to 0.25bit/pixel), the use of larger
64*64 blocks & the replacement of the cosine transform by
Wavelet transform.