Bitmap images are a map or a collection of individually colored, minute dots or pixels (picture elements) that are arrayed in a matrix or grid. Since each individual pixel is too small for the naked eye to perceive without the help of magnification, an array of these pixels forms a perceivably smooth graphic image.

Resizing Bitmap Images

The quality of a bitmap image depends mainly on its resolution, which is the number of dots or pixels per inch of space. Therefore, resizing bitmap images result in poorer image quality. Decreasing bitmap image size means decreasing pixels per inch so some pixels are removed. This results in less sharp images.

Increasing bit map image size means that new pixels would have to be created. These new pixels can only be approximations and not accurate replications of the original pixels. This results into splotchy images with lots of pixel noise.Bitmap Images

Bitmap Images Classifications

There are various color combinations to bitmap images. The number of colors present in bitmap images also varies. However, there are four main classifications of bitmap images.

Line Art Bitmap Images: These are the true black and white images since they only have two colors: black and white. These bitmap images are also called monochromes and they contain only 1 bit per pixel (bpp).

Grayscale Bitmap Images: Grayscale bitmap images have black, white and gray. They are called such because of the various shades of gray present.

Multitone Bitmap Images: This bitmap image classification encompasses all bitmap images that are composed of different color tones. The most common multitone bitmap images are those that use duotones but there are also tritones, quadtones and spot channel variations. Duotones are a mix of two colors like black and a pantone color. To the human eye, they appear like grayscale images with distinct color tones.

Full Color Bitmap Images: Full color images contain a variety of color. Their pixels' color information can be derived from various color models, the most common of which is the RGB color model that contains an assortment of colors that have resulted from different Red, Green and Blue combinations. Other color models used include CMYK and CIELAB.

Some Common Formats of Bitmap Images

Bitmap images can be saved in various formats. Following are the three most common formats.

BMP: This is the default graphic file format used by computers using the Windows operating system. RGB is the primary color model used by bmp bitmap images. A bmp file contains a bitmap-file header, a bitmap-information header, a color table, and the actual bitmap data.

GIF: Graphics Interchange Format is a file format that uses the copyrighted LZW compression algorithm. This format is suited to graphics posted on the Web and transmitted through the internet. There are two versions of GIF file formats: GIF 87a and GIF 89a.

JPEG: This is more properly known as JFIF or JPEG File Interchange Format. JPEG stands for Joint Photographic Experts Group. This file format can be used universally across various computing platforms.