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Image is an Artifact that reproduce the likeness of some subjects usually a physical object.

Images are pictures! A picture that represents visual information.

Used to save visual experiences. A picture is worth a 1000 words…I think

more!!!

How are non-digital images stored?Photographic filmCanvas/paintDigitally

Imaging is the process of acquiring images. Shorthand for image acquisition. Process of sensing our surroundings and then

representing the measurements that are made in the form of an image.

Passive imaging – employs energy sources that are already present in the scene.

Active imaging – involves use of artificial energy sources to probe our surroundings.

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Passive imaging is subject to the limitations of existing energy sources.

Passive Imaging Passive Imaging

Active imaging is not restrictive in this way but is invariably a more complicated & expensive procedure.

Active imaging predominates in medical field, where precise control over radiations sources is essential.

Active imaging is also an important tool in remote sensing.

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Active Imaging Active Imaging

Images stored in digital form!

Many ways of acquiring imagesScannerDigital CameraOthers…

Many ways of storing imagesGifTiffBMPJPGOthers…

JPEG (Joint Photographic Experts Group)

GIF (Graphic Interchange Format)

PNG (Portable Network Graphics)

TIFF (Tagged Image File Format)

PGM (Portable Gray Map)

FITS (Flexible Image Transport System)

BMP (Bitmap Format)

JPEG - Joint Photographic Experts Group

JPEG is designed with photographs in mind.

It is capable of handling all of the colors needed.JPEGs have a lossy way of compressing images.

At a low compression value, this is largely not noticeable, but at high compression, an image can become blurry and messy. .jpg

JPEG cautions:• Images with hard edges, high contrasts, angular areas, and

text suffer from JPEG compression.• Scanned “natural” photographs do not lose much,

especially at High or Maximum quality.• Only save finished images as JPEGs, every time you open

and save again, even if you don’t edit, you lose quality.• Always keep the original non-JPEG version (the native .psd

format).

So why use JPEG?• It is the best format for photographic images on the Web.• It’s compression ability is very great.

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GIF - Graphics Interchange Format

GIF is the most popular on the Internet, mainly because of its small file size. It is ideal for small navigational icons and simple diagrams and illustrations where accuracy is required, or graphics with large blocks of a single color. The format is loss-less, meaning it does not get blurry or messy.

The 256 color maximum is sometimes tight, and so it has the option to dither, which means create the needed color by mixing two or more available colors.

GIF use a simple technique called LZW compression to reduce the file sizes of images by finding repeated patterns, but this compression never degrades the image quality.

.GIF

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The GIF format is one of the most commonly used graphic file formats, especially on the Internet.

The GIF format is exceedingly useful in that it can contain animations. Its internal structure is such that it can store multiple images and the controls to make them appear as real time animation animated GIF.

The GIF format also allows a special color as to be specified as "using the background." This results in the image looks like transparent transparent GIF.

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Portable Network Graphic (PNG) which is pronounced as “Ping”.

Alternative to GIF, a lossless compression scheme is used.

Support three image type: true color, grayscale, palette-based (8-bit). JPEG supports the first 2. GIF supports the 3rd one.

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Advantages Better Compression

○ Deflate is an improved version of the Lempel-Ziv compression algorithm.

Improve Interlacing○ Display image quicker than Interlaced GIF.

True Color and Transparency○ Support 16-bit (Grey scale) or 48-bit (True Color)○ 16-bit for alpha channel (Transparency).

Gamma storage○ Store the gamma setting of the platform of the creator.

Disadvantages Not support by old browsers (Netscape 2,3,4 and IE 2,3,4)

TIFF - Tagged Image File Format

Widely used cross platform file format also designed for printing.

A bitmap image format.

TIFF supports lossless LZW compression which also makes it a

good archive format for Photoshop documents.

A popular format for grayscale images (8 bits/pixel) Closely-related formats are:

PBM (Portable Bitmap), for binary images (1 bit/pixel) PPM (Portable Pixelmap), for color images (24 bits/pixel)

- ASCII or binary (raw) storage

FITS - Flexible Image Transport System Format of a FITS file (http://fits.gsfc.nasa.gov)

Primary Header: metadata describing instrument, observation & file contents

Primary Data Array: array of 0-999 dimensions – usually a 2D image

+ none or more Extensions: Array, ASCII Table or Binary Table, each with

Header (New FITS-inspired XML format – VOTable)

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BMP - Bitmap Format

uses a pixel map which contains line by line information.

It is a very common format, as it got its start in Windows.

This format can cause an image to be super large.