Download - Digital Image processing
Digital Image
DIGITAL IMAGES are electronic snapshots taken of a scene or scanned from documents, such as photographs, manuscripts, printed texts, and artwork. The digital image is sampled and mapped as a grid of dots or picture elements (pixels).
Let’s go to the image root(Continue)
pixel
• A pixel (abbr. for picture element) is the smallest unit ofan image.
Let’s go to the image root(Continue)
• MATLAB (Matrix Laboratory) stores images asmatrices.
• In MATLAB, image pixels are referenced using (row,
col) values.
• Origin of the coordinate system (1,1) is the top leftcorner of the image
Let’s go to the image root
0.204.102 00000000 11001100 1100110
Image are two kinds:• Grayscale/Black-white image(16 bit image)Such as 11001100 1100110
Black white• RGB/Color image(24 bit image)Such as 00000000 11001100 1100110
Red(R) Green(G) Blue(B)
• Therefore, a 640x480 image is a matrix of 640 columns and 480 rows, each element of this matrix is called an image pixel.
In a summary
• Digital Image is nothing but collection of pixels which are arrange in matrix form
• Pixel is consists of sub pixels(black and white sub pixels for grayscale and red, blue and green sub pixels for color image)
• This sub pixels have value which represented in 8 bits binary number
What is Digital Image processing?
• Digital image processing is the is a method to convert an digital Image in order to get an enhanced image or to extract some useful information from it by using computer algorithms
Smoothing Image(Gaussian blur method)
1/91/9
1/91/9
1/91/9
1/91/9
1/9
Origin x
y Image f (x, y)
e = 1/9*106 + 1/9*104 + 1/9*100 + 1/9*108 + 1/9*99 + 1/9*98 + 1/9*95 + 1/9*90 + 1/9*85
= 98.3333
FilterSimple 3*3
Neighbourhood106
104
99
95
100 108
98
90 85
1/91/9
1/9
1/91/9
1/9
1/91/9
1/9
3*3 Smoothing
Filter
104 100 108
99 106 98
95 90 85
Original Image
Pixels
*
The above is repeated for every pixel in the
original image to generate the smoothed image
Image Smoothing Example
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Normal Image
Image Smoothing Example
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Using 3*3 filter
Image Smoothing Example
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Using 5*5 filter
Image Smoothing Example
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Using 9*9 filter
Image Compression(Delta Encoding)
Process of delta encoding
• Instate of every pixel value we consider group of pixels where nearby pixels are most similar
• We give value according to similarity which
called delta value
• If neighbor pixels are identical then delta value=0
Image Compression(Delta Encoding)
Continue
• If almost identical then close to 0
• In a high regulation image neighbor pixels are a lot more identical so the delta value looks like this
• If we consider this
• We can express the group of pixel like this
• Png image follow this Encoding which is lossless compression