Describe ways to reduce file size and identify specific file types.

What will be an ideal response?

You can decrease file size by shrinking the physical dimensions of an image, saving it in a compressed file format, or reducing its color depth.

Shrinking the physical dimensions of an image allows you to reduce its file size. A 2" X 2" image can be stored in a file that is one-quarter the size of the same image at 4" X 4". Most graphics software provides a tool to resize an image.

You can also use compression techniques to decrease image file size. Some file formats provide built-in compression that reduces file size simply by using a more effective storage technique. For example, when stored in non-compressed BMP or TIFF format, an image might require about 950 KB of storage space. Using JPEG format with built-in compression, the file size can be reduced to 48 KB.

As you learned in an earlier chapter, images can be compressed using lossy or lossless compression. PNG and GIF formats are lossless. JPEG uses lossy compression. Be careful when working with JPEG images because lossy compression discards data every time you save the image. This generation loss can lead to images becoming increasingly blurrier with successive saves.

A true-color graphic requires 24 bits for each dot of color in an image, whereas a 256-color graphic requires only 8 bits. Therefore, by reducing the color depth from true color to 256 color, the image file shrinks to one-third of its original size. When combined with compression techniques, color reduction can significantly shrink file size. Unfortunately, reducing color depth can reduce image quality. You'll have to view the converted image to evaluate if it is acceptable.