Chapter I Digital Imaging Fundamentals http://www.kodak.com/country/US/en/digital/dlc/book3/chapter1/index.shtml

Chapter I, Digital Imaging Fundamentals: Lesson I The Digital Image http://www.kodak.com/country/US/en/digital/dlc/book3/chapter1/digFund1.shtml

This course provides a fundamental understanding of how film images are captured, processed, stored and output digitally. Each module is followed by a brief review and also by a competency exam for that module.                       Lesson 1. The Digital Image In this module, we'll explore the fundamental properties of the digital photographic image. Analog and Digital Vector and Raster Graphics Image Quality Review Questions

In this module, we'll explore the fundamental properties of the digital photographic image.                              Digital imaging products like Photo CD, enable us to capture and store film images electronically, then process them on the computer, much like we process text and drawings. A film image is represented electronically by continuous analog wave forms. A digital image is represented by digital values derived from sampling the analog image.

Analog values are continuous Analog values are continuous. Digital values are discrete electronic pulses that have been translated into strings of zeros and ones the only digits in a binary numbering system.

Before we take a closer look at the photographic digital image, we need to understand the difference between two ways the computer stores image data: Vector graphics and Raster graphics.

Vector graphics, also known as object-oriented graphics, are created in various drawing programs.

                             Vector images are stored as a display list describing the location and properties of the objects making up the image, such as shapes, arcs and lines.

Raster graphics, also known as bit-mapped graphics, are created by scanners and digital cameras. From this point on in this course, we'll be talking about raster images.

Raster images are "painted" across the computer screen in an array of square elements called pixels. Pixel is short for picture element.

                             Each pixel is stored in an area of memory called a bit-map. Each pixel has a numbered address.

Storing the formula for creating a vector image takes only a few kilobytes. Storing the location and value of each pixel in a raster image can take thousands of times more memory.

The quality of a raster image is determined at capture by two factors: spatial resolution and brightness resolution.

As we will see in the Capture Module, pixel size is determined by the rate at which the scanner samples the image. A long sampling interval produces an image low in spatial resolution. A shorter interval produces higher spatial resolution.

The brightness or color value of each pixel is defined by one bit or by a group of bits. The more bits used, the higher the brightness resolution.

A 1-bit image can have only 2 values, black or white A 1-bit image can have only 2 values, black or white. 1-bit images simulate grays by grouping black and white pixels. This process is called dithering or halftoning.

An 8-bit gray-scale image displays 256 levels of brightness An 8-bit gray-scale image displays 256 levels of brightness. Each pixel is black, white or one of 254 shades of gray.

A higher resolution 12-bit medical image provides more than 4000 brightness levels.

In a 24-bit image, each pixel is described by three 8-bit sets of numbers representing the brightness values for red, green and blue.

High resolution 24-bit images display 16.7 million colors.

Each pixel in a 24-bit image has one of 256 brightness values for red, green and blue.

Lesson Review Let's review what we've learned so far. Select the raster image.                       

This is the Raster image End of Unit 1