What Is a Raster or Bitmap Image? GA S REGULAR Menu Lifewire Tech for Humans Newsletter! Search Close GO Software & Apps > Design

Definition of Bitmap and Raster Image

Bitmaps and raster images are the same thing—but different from vectors

By Sue Chastain Sue Chastain Writer St. Petersburg College Sue Chastain is a former Lifewire writer and a graphics software authority with web design and print publishing credentials. She's also skilled in WordPress administration. lifewire's editorial guidelines Updated on April 17, 2020 Tweet Share Email ryccio / Getty Images Tweet Share Email Design Graphic Design Photoshop Animation & Video 3D Design Bitmap-based images are comprised of pixels in a grid. Each pixel or "bit" in the image contains information about the color to be displayed. Bitmap images offer a fixed resolution and cannot be resized without losing image quality. These images are also called raster images. The alternative to a bitmap is a vector image, which instead of dots use embedded instructions to draw lines on paths. A vector may be infinitely resized with no loss in image quality.

All About Pixels

Each pixel on your screen is, in very simple terms, a "bit" of color information used to display the image on a screen. That screen could be as small as the one on an Apple Watch or as large as a pixel board found in Times Square. Along with needing to know the three colors (red, green, blue) applied to the pixel another "bit" of information is where, exactly, that pixel is located in the image. These pixels are created when the image is captured. Thus if your camera captures an image at 1280 pixels across and 720 pixels, down there are 921,600 individual pixels in the image and each pixel's color and location must be remembered and rendered. If you double the size of the image, the pixels get larger and the file size increases because the same number of pixels are now in a larger area. No pixels are added. If you reduce the size of the image the same number of pixels are in a smaller area and, as such, the file size reduces.

How Resolution Factors In

One other factor that affects bitmaps is the resolution. The resolution is fixed when the image is created. Many of today's modern digital cameras, for example, capture images with a 300 dpi resolution. This explains why digital camera images can be rather huge. There are a ton more pixels to be mapped and colored than commonly found on a normal computer display.

Typical Bitmap-Based Formats

Common bitmap-based formats are JPEG, GIF, TIFF, PNG, PICT, and BMP. Most bitmap images can be converted to other bitmap-based formats very easily. Bitmap images tend to have much large file sizes than vector graphics and they are often compressed to reduce their size. Although many graphics formats are bitmap-based, bitmap (BMP) is also a graphic format—although its use today is very rare. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire Vector vs. Bitmap Images How to Resize Multiple Files with Photoshop Elements SVG Files: What They Are and How to Open & Convert Them What Is a GIF? 10 Best Free Photo Resizers 7 Best Free Image Hosting Websites 9 Best Free Image Converter Software Programs What Is the Screen Door Effect? Preparing Images for Mobile Devices How to Smooth Out Jagged Lines in a Bitmap Image What to Look for When Buying a Projector How to Make High-Resolution Images The Benefits of Using SVG Images on Your Website HDR vs. 4K: What's the Difference? PCX File (What It Is and How to Open One) Use a Digital Camera as a Scanner Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies