A bitmap is a mapped array of pixels that can be saved as a file.

Both JPEG and GIF are bitmap graphic formats. Currently, the only other way to store an image is as a vector graphic. You can’t easily scale bitmap images, but you can control every single pixel and thus achieve many effects impossible in vector graphics. Conversely, vector formats offer advantages of scalability and lower bandwidth requirements. When you compress a bitmapped image, you suck out some of the visual information.

To bypass this, the portable network graphics format (or PNG, pronounced “ping”) was designed to store a single bitmap image for transmittal over computer networks without losing this data.

Bit depth describes the file size of an image by orders of magnitude.

When wrangling with file size versus image quality, it’s often important to minimize the bit depth of an image while maximizing the number of colors. To calculate the maximum number of colors for an image of a particular bit depth, remember that the number of colors is equal to two to the power of what the bit depth is. For example, a GIF can support up to eight bits per pixel, and therefore can have as a many as 256 colors, since two to the power of eight equals 256.

Dots per inch (DPI) measures the resolution of images on a screen or printed page. The more dots, the better the resolution