Learn in the textbookData Representation Methods for Still Images
DefinitionBitmap data (ビットマップデータ) is image data that records each pixel's color as a sequence of bits, and the term means almost the same as raster data.
ExplanationThe more bits assigned to each pixel, the more colors it can show: black and white need just 1 bit, while full color with about 16.77 million colors needs 24 bits. The BMP format is a typical file format that saves images this way.
AnalogyIt is like a sheet of graph paper with a color number written in each square. Read the numbers in order and you can paint the original picture again.
Memory hookRemember it literally: bits laid out to match positions on the screen, like a map.