IMAGE DISPLAY

        

         The image display is the method of image to visible in digital media. Digital image data displaying or concept of image sampling is the number of pixel in rows and columns. Each pixel has some value in RGB colours. (Read, Green, Blue), these dimensions are stored as Digital Number values (DN). Image create with pixels in regular grid format (rows and columns). DN numbers representing the value of brightness of the pixel. These digital images captured from RS satellite sensors according to their reflection wavelengths.

Location of a pixel

Pixel location measured from grid of columns and rows. The X coordinate specifies the column of the grid and the Y coordinate specifies the row. The upper left corner of the image always begin at 0,0 value.

Calculating File size

{(( x * y * b )) * n} = Output file size

Y = rows

X = columns

b = number of bytes per pixel

n = number of bands

As a example, in 7 band land sat image 8 bit file with 400 rows and 500 columns, find out how much space needed.

500 x 400 x 1 x 7 = 1400000 bytes

ERDAS IMAGINE files

When data imported into ERDAS IMAGINE, they converted to ERDAS IMAGINE file format. This ERDAS IMAGINE stored in two types

Thematic – This raster layer contain qualitative, categorical information about soils, Land use, Roads, Hydrology.

Continuous – This raster layer contain quantitative and related, continuous values. These layers can be Multiband like SPOT panchromatic data)

What is Multispectral Band?

Sat image or Digital image of an area captured in different spectral ranges or bands. This band can be dissimilar according to the type of RS sat.

Visualization of Image Data

Histogram

The histogram describes the distribution of the pixel values of that image, the range between 0 – 255.

Single band image

Histogram is used to obtain optimum display of single band images. Normal single band images display using grey scale. It digital value range is from 0 (Black) to 255 (White).

Color image

Combination of red, green and blue channels of a digital display images. In each pixel, the primary colors are combined in different scope depending on the 3 bands DN values to represent different colors.