Digital Image Fundamentals: Representation, Color Models, and Acquisition

Digital Images: An Introduction

With the advancement of technology, the use of images in computer systems has been increasingly employed. These applications are present in various fields, including:

• Web pages and graphical interfaces
• Multimedia programs and games
• Educational programs and desktop publishing
• Computer graphics and medicine
• Computer vision and image processing

Thus, it becomes increasingly important that computer professionals acquire the necessary knowledge to effectively utilize this resource.

Representation of Digital Images

To better understand how images are acquired and stored, we must first examine how they are represented digitally. Representing an image involves modeling it so that its data can be interpreted by a computer.

The images discussed here are two-dimensional. That is, even if an image represents a three-dimensional object, it is treated as a projection of that object, similar to a photograph. Although three-dimensional images can be represented (modeled), we will not address this type of image in this work.

Vector Representation and Color Standards

The CIE (International Commission on Illumination) is the body responsible for standardization in the fields of photometry and colorimetry. The CIE has established several color patterns, including CIERGB and CIE-XYZ.

We will focus here on the CIE-RGB system [2]. Defined by the CIE in 1931, this model defines a representation space for trichromatic RGB, utilizing three basic colors corresponding to the low, medium, and high frequency bands of the spectrum:

• Red (R)
• Green (G)
• Blue (B)

This is why the system is called CIE-RGB. Images are represented by these RGB components; that is, each primary color component (R, G, and B) has an intensity level used to form other colors. We will examine how matrix images can be represented based on the number of colors and device limitations.

Color Image Representation Methods

The representation of color images can be achieved using several methods:

• True Color (using color components)
• Indexed Color
• Fixed Colors

The choice of representation method depends on the intended purpose and the specific devices used to handle the images.

Digital Image Acquisition

The process of acquiring digital images involves transforming real-world images into a digital format. This transformation is performed using graphical input devices.

Depending on the type and destination of the image, these graphical input devices can be classified as either vector or array (raster) devices.