IIT Bombay Slide 1 July 31, 2014 Lecture 05 Image Display and Data Formats Contents of the Lecture Display of Remotely Sensed Images • False color composites • Natural color composites • Gray scale images Interleaving Formats for Multiband Images • BIL • BSQ • BIP Impact of Resolution on File Sizes GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 2 Image Display Red Gun Image Data Green Gun on Disk Blue Gun Image Display System GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 3 Concept of a Color Composite • In order to generate a color display of a satellite image on the monitor, we need to choose – Data to represent in red color – Data to represent in green color – Data to represent in blue color • Such a display is known as a color composite GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 4 False Color Composite • A False Color Composite (FCC) is formed when the data assigned to red / green / blue color on the display is collected outside the visible region • A standard FCC comprises: Wavelength of Data Display – Near Infrared wavelength Red Color – Red wavelength Green Color – Green wavelength Blue color GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 4a Reflectance Spectra of Earth Objects GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 5 Example of FCC GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 5a Example of FCC GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 5b 23.25m x 23.25m GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 6 Natural Color Composite • A Natural Color Composite (NCC) is formed when the data assigned to red/green/blue is collected in the same wavelengths • For instance: Wavelength of Data Display – Red wavelength Red Color – Green wavelength Green Color – Blue wavelength Blue color GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 7 Natural Color Composite GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 7a GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 7b BHUVAN (2D) – PART OF MUMBAI GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 8 Black & White Image • A black/white image is one that has no color but only white, black and shades of gray. • The smallest value at a pixel is 0 (black) • The largest value is 2 L -1 (white) • Intermediate values represent shades of gray, from black increasing towards white • For L=8, black = 0, white = 255 GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 9 Gray Scale black dark gray light gray white GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 10 Gray Scale Images • Examples of gray scale images in R.S. – An image of a single band of a multisp. image – An image from radar sensor (SAR image) – An image from panchromatic sensor • How does this happen on a display monitor? When Red, Green and Blue display guns are fed the same signal, the resulting display on the screen will be black&white GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 11 Panchromatic Image MUMBAI Data: IRS-1C, PAN Consists of 1024x1024 pixels. GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 11a Panchromatic Image Bangalore Data: SPOT, PLA Consists of 1024x1024 pixels. GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 11b Pseudocolor Image A selected range of gray levels is assigned an artificial color for highlighting the feature that is originally found in that range http://earthobservatory.nasa.gov/IOTD/view A number of eddies visible in the Pacific Ocean in this pseudo-color scene. GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 11b Pseudocolor Image http://911encyclopedia.com/wiki/index.php/AVIRI GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 12 Common Data Structures to Store Multiband Data GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 13 Common Data Structures to Store Multiband Data • BIL – band interleaved by line • BSQ – band sequential • BIP – band interleaved by pixel GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 14 Image Acquisition Optics Band 1 Band 2 Band 3 … Width equal to Direction of pixel width Ground satellite motion GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 15 BIL • Band interleaved by line storage format – MxN Image; K Bands; One row on ground B 11 B 12 … B 1N B 21 B 22 … B 2N … B k1 B k2 … B kN • A single file on disk or CD contains M.K rows, each having N columns; Every K rows in the file correspond to ONE ROW ON THE GROUND GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 16 Band 1 Row1 Image Size … M rows BIL FILE Band K Row1 Band1 Row2 STRUCTURE N columns … K Bands Band K Row2 … Band 1 Row M … Band K Row M GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 17 BIL • BIL is a popular format for storing multispectral images, and supported by most remote sensing software (ERDAS, PCI, …) • Well suited when multiband data analysis is required • Lot of data I/O involved when access to a single band image is needed on sequential access systems. Moderate overhead on random access systems GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 18 BSQ • Band sequential method involves storing one full single band image after another B 11 B 12 … B 1N B 21 B 22 … B 2N … B M1 B M2 … B MN • The image for the second band, …, up to Band K follow GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 19 BSQ FILE STRUCTURE Band 1 Row 1 … Band 1 Band 1 Row M Band2 Row 1 … Image Size Band 2 Band 2 Row M M rows … N columns Band K Row 1 … Band K K Bands Band K Row M GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 20 BSQ • Ideally suited when the multiband image is processed one band at a time, such as image enhancement, neighbourhood filtering, etc. • More overheads when all band values are required at each pixel GNR607 Lecture 05 B. Krishna Mohan
IIT Bombay Slide 21 BIP • Band interleaved by pixel – Commonly used for storing color images, with red, green and blue values alternating • R G B R G B R G B … – Not used in present times to store satellite images – Used in the early stages of Landsat data distribution GNR607 Lecture 05 B. Krishna Mohan
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