What is a Raster Image?

A raster image, also known as a bitmap image, is an image composed of pixels arranged in a grid. Each pixel has a specific color and, when viewed together, these pixels form the entire image.

Characteristics of a Raster Image

Raster images have a number of characteristics:

• Fixed resolution: once an image is rasterized, it has a specific number of pixels wide by a specific number of pixels high. If you try to enlarge a raster image beyond its original resolution, it may appear blurry or pixelated.
• Detailed editing: Raster images are ideal for photo editing and other detailed work because you can modify each pixel individually.
• Larger file size: Detail-rich, high-resolution images can generate large files, especially in uncompressed formats.

Vector images , on the other hand, which are the opposite of raster images, rely on mathematical formulas and points to define shapes, lines and curves. Vectors can be scaled to any size without losing quality and are ideal for graphics such as logos, icons and diagrams.

Raster image formats (bitmap)

There are different types of raster images, each with its own characteristics, so they are often used in different contexts:

JPEG (Joint Photographic Experts Group)

• Widely used for photographs.
• Uses lossy compression, which means that the image quality can be reduced to reduce the file size.

PNG (Portable Network Graphics)

• Supports transparencies.
• Uses lossless compression.

GIF (Graphics Interchange Format)

• Formerly used for web images.
• Supports animations.
• Limited to 256 colors.

BMP (Bitmap)

• Uncompressed format originated in Windows.
• Generally larger file size than other formats.

TIFF (Tagged Image File Format)

• High quality.
• Widely used in the printing and publishing industry.
• Supports multiple layers and lossless compression.

WebP

• Developed by Google.
• Combines features of JPEG and PNG.
• Supports lossy and lossless images, as well as transparencies.

Where are Raster Images used?

Due to their characteristics, bitmap images are used in a large number of areas:

• Digital photography: digital cameras capture images in raster formats, such as JPEG or RAW. This is because these images are composed of pixels, making it possible to represent the subtle details and tones of a photographed scene.
• Web design: The images you see on most web pages are rasterized. This includes banners, photographs, background images and more. Formats such as JPEG, PNG and GIF are common in this area.
• Print: Magazines, brochures, posters and other printed materials often use raster images to represent photographs or illustrations with a lot of detail.
• Image editing: Image editing programs, such as Adobe Photoshop or GIMP, are primarily designed to work with raster images. These programs allow users to manipulate and edit individual pixels.
• Video games: Video games use raster textures to give a detailed and realistic look to 3D models.
• Video and animation: The images that make up the frames of a video are rasterized. Animation and video production are based on this type of images.
• Applications in science and technology: In areas such as medicine, astronomy and geography, raster images (such as CT scans, satellite images or micrographs) are essential because of their ability to represent accurate and detailed data.

Advantages of Raster Images over Vector Images

Raster images offer a number of advantages over vectorized images:

• Detail and Depth: Raster images can represent extremely fine details, such as textures, shadows, gradients, and subtle color variations. This is very important for photographs and digital artwork that require a high level of detail.
• Compatibility: bitmap images, especially in formats such as JPEG and PNG, are widely recognized and compatible with a wide variety of devices, operating systems and programs.
• Better effects rendering: They can display effects such as blur, noise, and lighting effects more naturally and realistically than vector images.

Discover many other important terms in our graphic design dictionary, in which we delve into a large number of concepts that every design and editing professional should know.