Page 10 - DCAP504_Computer Graphics

Unit 1: Fundamentals of Computer Graphics

another possible order is the vice versa of the normal order. The other function of the image data
format is that it specifies whether the RGB values are interlaced in the color map or in the image. When
the values are in an interlaced fashion, the RGB components for an exact pixel stay together
consecutively. This is followed by the three color components for the next entry or pixel. Therefore, the
color values in the image data section are a sequence of red, green, blue…, red, green, blue, and so on.

When the values are in non-interlaced fashion, the values of one primary color for all pixels or table
entries come first, and then the values of another primary color appear. This is followed by the values of
third primary color. Therefore, the image data is in the form of red, red…, green, green…, blue, blue.
The image data’s values may be compressed with the help of a compression algorithm, such as Run
Length Encoding (RLE) algorithm. The main idea of RLE can be demonstrated with a character string
“xxxxxxyyzzzz”, which takes 12 bytes of storage. At this instant, if the string is scanned from left to
right for segments of repeating characters, and each segment is substituted by 1 byte, the count is
repeated when the character being followed is also repeated. The compression or conversion of the
given string to “6x2y4z”, which takes only 6 bytes will be easy to do. This converted or compressed
version can be expanded or decompressed, by repeating the character following each repeat count to
recover the actual string.

The file header’s length is often fixed. If it is not fixed, then it is important to include the length
information in the header, to indicate where exactly the image data starts.

Some of the image data file formats include header length. The length of every
component in the image data section is dependent on certain factors, such as
compression type and image type. In addition, format specific information can also be
found in the header.
1.2 Image Processing and User Interface

Computer graphics consists of many important elements, which make it appropriate for every field.
Two such elements are image processing and user interface. These two concepts must be understood for
the clear understanding of different concepts related to images, such as image representation, image
display, and so on.
1.2.1 Image Processing
Image processing is a method used to enhance or develop raw images. Raw images refer to the images
that are taken by cameras, satellites, space probes, and aircrafts or even pictures that are taken in our
normal day-to-day lives.
During the last four to five decades, many techniques have evolved in image processing. Most of the
various techniques are created to enhance images obtained from space probes, unmanned spacecrafts,
and military investigation flights. Image processing systems are becoming prominent. The prominence
is due to accessibility of large size memory devices, powerful personal computers, graphics software,
and so on.
Today, image processing is applied in many fields, such as, medical imaging, remote sensing, forensic
studies, textiles, military, film industry, document processing, graphic arts, printing industry, and so
on.
There are four steps in image processing. These steps are:
1. Image Scanning: It is the action or process of converting the images to digital images.
2. Storing: It is nothing, but the way the image is stored.

Drawing applications store pictures, spreadsheet applications store charts,
Computer Aided Design (CAD) applications store drawings.
3. Enhancing: It is a process aimed at enhancing the visual appearance of an image.

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