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What is a Raster Image?

Raster images surround us at every moment, from photography on smartphones to all the graphics we find on websites. Therefore, if your company is geospatial-focused or mapping-based, like GeoWGS84.com, being knowledgeable about raster data is imperative.


This guide will explain what raster images are, how raster images work, the advantages/disadvantages of raster image usage, as well as the way raster images are integrated with GIS and web applications.


Raster Image
Raster Image

What are Raster Images?


A raster image (aka bitmap) is a type of digital image made up of tiny dots/tiles/pixels; therefore, each pixel will have its own value for colour/intensity, and all of those pixel values collected create one complete image.


To picture how a raster image works, you can imagine that you have a mosaic (each tile in the mosaic representing a pixel), which creates the image as a whole, and therefore all of the mosaic tiles (pixels) represent one complete image of some content.


How Raster Images Work


A raster image is made up of a series of cells arranged in a grid pattern. Each cell is called a pixel, which has an associated value representing its color and/or brightness. The final display quality and file size depend on the resolution of an image (for example, 1920 across by 1080 down).


Three main components define a raster image:


  • Pixel (Picture Element): The smallest component of a raster image.

  • Resolution: The number of pixels per inch (PPI) or dots per inch (DPI).

  • Color Depth: The number of bits available to represent each pixel's color.


As a general rule, higher-quality images require higher-resolution images, which leads to larger images.


Common Raster Image Formats


  • JPEG - Best For Photographs - Uses Lossy Compression

  • PNG - Supports Transparency - Uses Lossless Compression

  • GIF - Limited Number Of Colours

  • TIFF - High-Quality Format - Mostly Used For Printing Or GIS Data

  • BMP - Uncompressed Media Format With High Storage Size, And Thereby, Large Files.


Raster vs. Vector Images


Understanding the difference between raster and vector images is critical:

Feature

Raster Images

Vector Images

Structure

Pixel-based grid

Mathematical paths

Scalability

Loses quality when enlarged

Infinitely scalable

File Size

Larger (especially high-res)

Usually smaller

Use Cases

Photos, satellite imagery

Logos, icons, illustrations


Benefits of raster images


  • High resolution and detail make them suitable for intricate images, such as photographs.

  • They are supported on nearly all types of devices and browsers.

  • They provide smooth gradients of colors.


Limitations of raster images


  • The quality degrades at different sizes.

  • Raster images can have very large file sizes, especially when using high-resolution images.

  • Editing of individual elements within a raster is typically more complex than with vector graphics.


Uses for raster images in GIS applications


Raster images are an integral component of geographic information systems (GIS), particularly with the use of sites such as GeoWGS84.com.


Common uses include:



Each pixel contained within a GIS raster is a representation of a real-world value, such as the value of the elevation of the pixels, the temperature, or the vegetation index of each pixel.


When to Use Raster Images


Use raster images when:


  • You want to depict a photograph or a continuous tone image.

  • You are creating a project that uses aerial/satellite images.

  • You require a high level of colour and tone representation in the gradient.


Best Practices for Using Raster Images on Websites


To increase the performance of your raster images on the web, you should:


  • Compress your images using tools such as TinyPNG.

  • Select the correct format (JPEG for photos, PNG for transparency)

  • Use responsive images to address different screen sizes (e.g., iPhone and widescreen computer monitor).

  • Optimize resolutions to provide a balance of quality and speed.


Raster images represent the building blocks of digitizing images/gis analysis. Their pixel-based characteristics make them suited to visible representations(e.g., pictures & aerial/satellite images) that require high levels of detail versus a trade-off in the scalability of image files.


For example, GeoWGS84.com relies heavily on raster images for its mapping, analyzing, and visualising functions. A further understanding of raster images will help you make better decisions in web development and GIS workflows.


For more information or any questions regarding the raster image, please don't hesitate to contact us at


USA (HQ): (720) 702–4849

India: 98260-76466 - Pradeep Shrivastava

Canada: (519) 590 9999

Mexico: 55 5941 3755

UK & Spain: +44 12358 56710


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