Raster Image

May 20, 2023

A raster image, also known as a bitmap, is a type of digital image that is made up of a grid of individual pixels. Each pixel in the grid is assigned a specific color value, and together they form the picture. Raster images are commonly used in digital photography, graphic design, and web development.

Purpose and Usage

The purpose of a raster image is to represent a visual image using a matrix of pixels. Raster images are often used for photographs or images with complex color schemes, such as illustrations or logos. They are also useful for creating realistic textures or gradients.

Raster images are used in many different areas of digital design, including web design, graphic design, and video production. In web design, raster images are commonly used for backgrounds, buttons, and other graphical elements. In graphic design, raster images are used for creating mockups, designing logos, and creating illustrations. In video production, raster images are used for creating special effects and compositing.

File Formats

Raster images can be saved in a variety of file formats, including JPEG, PNG, and TIFF. Each format has its own strengths and weaknesses, and the choice of format depends on the intended use of the image.


JPEG (short for Joint Photographic Experts Group) is a commonly used file format for raster images. JPEG files are compressed, which means they are smaller in size than other file formats. However, this compression also means that some image quality is lost. JPEGs are best used for photographs or images with complex color schemes.


PNG (short for Portable Network Graphics) is another file format commonly used for raster images. PNG files are lossless, which means they maintain their quality even after multiple edits. PNGs are best used for images with transparent backgrounds or for images that require high-quality reproduction.


TIFF (short for Tagged Image File Format) is a high-quality file format for raster images. TIFF files are lossless and are often used in professional printing and publishing. However, they are also larger in size than other file formats, which can make them difficult to use on the web.


The resolution of a raster image refers to the number of pixels in the image. The higher the resolution, the more detail the image will have. However, high-resolution images also take up more storage space and can be slower to load on the web.

Resolution is measured in pixels per inch (ppi) or dots per inch (dpi). For web images, a resolution of 72 ppi is usually sufficient. For print images, a higher resolution is required, typically between 300 and 600 dpi.

Image Size

The size of a raster image is determined by the number of pixels in the image. The larger the number of pixels, the larger the image size. The size of a raster image is measured in pixels or inches.

When creating raster images for the web, it is important to keep the file size as small as possible to ensure fast loading times. This can be achieved by reducing the image size and compressing the file.


Raster images are easily edited using image editing software such as Adobe Photoshop or GIMP. Common edits include adjusting the brightness and contrast, cropping the image, or applying filters.

However, editing a raster image can lead to a loss of quality. Each time an image is saved after editing, the compression algorithm is applied again, which can reduce the image quality. To avoid this, it is best to work with the highest-quality version of the image possible.

Advantages of Raster Images

  1. Realistic: Raster images are capable of representing complex color schemes and textures in a realistic way.
  2. Flexibility: Raster images can be easily edited using image editing software, making them a flexible option for digital design.
  3. Widespread compatibility: Raster images can be saved in a variety of file formats, making them compatible with a wide range of software and devices.

Disadvantages of Raster Images

  1. Loss of quality: Raster images can lose quality when edited or saved. This can reduce the overall visual appeal of the image.
  2. Limited scalability: Raster images are limited in their scalability due to their fixed pixel count. When enlarged beyond their original size, raster images can become pixelated.
  3. Large file sizes: Raster images can have large file sizes, which can lead to slow loading times on the web.