Concept of PIXELS
Pixel
Pixel is the smallest
element of an image. Each pixel correspond to any one value. In an 8-bit gray
scale image, the value of the pixel between 0 and 255. The value of a pixel at
any point correspond to the intensity of the light photons striking at that
point. Each pixel store a value proportional to the light intensity at that
particular location.
PEL
A pixel is also known as PEL. You can have more understanding of
the pixel from the pictures given below.
In the above picture, there may be thousands of pixels, that
together make up this image. We will zoom that image to the extent that we are
able to see some pixels division. It is shown in the image below.
Relationship with CCD array
We have seen that how an image is formed in the CCD array. So a
pixel can also be defined as
The smallest division the CCD array is also known as pixel.
Each division of CCD array contains the value against the intensity
of the photon striking to it. This value can also be called as a pixel.
Calculation of total number of pixels
We have define an image as a two dimensional signal or matrix.
Then in that case the number of PEL would be equal to the number of rows
multiply with number of columns.
This can be mathematically represented as below:
Total number of pixels = number of rows ( X ) number of columns
Or we can say that the number of (x,y) coordinate pairs make up
the total number of pixels.
We will look in more detail in the tutorial of image types, that
how do we calculate the pixels in a color image.
Gray level
The value of the pixel at any point denotes the intensity of image
at that location, and that is also known as gray level.
We will see in more detail about the value of the pixels in the
image storage and bits per pixel tutorial, but for now we will just look at the
concept of only one pixel value.
Pixel value.(0)
As it has already been define in the beginning of this tutorial,
that each pixel can have only one value and each value denotes the intensity of
light at that point of the image.
We will now look at a very unique value 0. The
value 0 means absence of light. It means that 0 denotes dark, and it further
means that when ever a pixel has a value of 0, it means at that point, black
color would be formed.
Have a look at this
image matrix
Now this image matrix
has all filled up with 0. All the pixels have a value of 0. If we were to
calculate the total number of pixels form this matrix, this is how we are going
to do it.
Total no of pixels =
total no. of rows X total no. of columns
= 3 X 3
= 9.
It means that an
image would be formed with 9 pixels, and that image would have a dimension of 3
rows and 3 column and most importantly that image would be black.
The resulting image that
would be made would be something like this
Now why is this image
all black. Because all the pixels in the image had a value of 0.
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