bitwiseLeftShiftOp.md

Bitwise Left Shift Operator

Introduction

Say we're asked to find out left shifted bit string of a given bit string B, what do we do ?

B = 10101011

Shift B by 2 places leftward

B = B << 2 = 1010101100

We already know this, for a 8-bit image, we can have 256 different color levels & for a color image we'll just keep three color components ( R, G & B ) each of them will be 8-bit lengthy.

With 8-bits max unsigned integer that can be represented is 256 i.e. all pixel intensity values lie in [0, 255] range.

But if we've one pixel intensity 255 ( in binary 11111111 ) and asked to shift it by 1 place leftward, obtained value ( 510 ) will definitely be not in valid pixel intensity range. So we need to put pixel intensity value back into range, by using either of following two mechanisms

• Clip pixel intensity values i.e. I(x, y) = I(x, y) < 0 ? 0 : ( I(x, y) > 255 ? 255 : I(x, y) )
• Scale pixel intensity value i.e. I(x, y) = I(x, y) % 256

So what we gonna do for an image is like below

• Given an image, keep picking up each row of pixels and putting into an worker to be executed by different thread of execution that main.
• Each worker will apply bit wise left shift operator on each pixel intensity along provided row.
• Finally stores resulting image into sink buffer ( different that source image buffer ).

Result

Source	Shift By	Clipped	Sink
	1	true
	1	false
	2	true
	2	false
	3	true
	3	false
	4	true
	4	false

Thanking you