Introduction

Computer Graphics refers to anything involved in the creation or manipulation of images on a computer, including animated images.

Raster graphics are composed of pixels.

Vector graphics are composed of paths/shapes.

Vector graphics represent an image as a list of the geometric shapes that it contains. The shapes can also have attributes, such as the thickness of a line or the color that fills a shape etc.

More rich and detailed images uses Raster graphics.

A pixel is the smallest addressable element of a picture represented on a screen, a physical point in a picture.

An image that is presented on the computer screen is made up of collection of pixels referred as bitmap.

In CG, a bitmap is a mapping from some domain (eg. a range of integers) to bits values(0/1). It is also called a bit array or bitmap index.

• The more general term pixmap refers to a map of pixels, where each pixel may store more than two colors, thus using more than one bit per pixel.
• In some contexts, the term bitmap implies one bit per pixel, while pixmap is used for images with multiple bits per pixel.
• The screen consists of a rectangular grid of pixels, arranged in rows and columns.
  • Resolution of a screen is just the number of pixels in WxH.
  • Aspect ratio of the screen is the ratio of (number of pixels in width / number of pixels in height).
• At a given time, each pixel can show only one color.
  • The color of the pixel can be determined using different formats(color space) like RGB, RGBA, Grayscale, Indexed color etc.

The color values for all the pixels on the screen are stored in a large block of memory known as a frame buffer.

• Changing the image on the screen requires changing color values that are stored in the frame buffer.

Graphics API and Library

A graphics library is a program library designed to aid in rendering computer graphics to a monitor. This typically involves providing optimized versions of functions that handle common rendering tasks.

• This can be done purely in software and running on the CPU, common in embedded systems, or being hardware accelerated by a GPU, more common in PCs.
• By employing these functions, a program can assemble an image to be output to a monitor.
• This relieves the programmer of the task of creating and optimizing these functions, and allows them to focus on building the graphics program.

Graphics libraries are mainly used in video games and simulations.