What is a bitmapped image?
Bitmaps (GIF, JPG, TIF) store information about an image pixel by pixel. A GIF file, say, might contain information on ten thousand pixels. When read, the file says to the computer, ‘OK, pixel 1 is gray, pixel 2 is a slightly darker gray, pixel 3 is…’ and so on. Only much quicker. The problem is that any bitmapped file can only contain information about the number of pixels it was originally designed to contain when you put it together in Photoshop or Paint. So if you try to make it bigger, the pixels have to get bigger and your image begins to look chunky and jagged.
