Raster images, also known as bitmap images, are a type of digital image that is composed of a grid of individual pixels. Each pixel in a raster image represents a specific color or shade, and when combined, these pixels form a complete picture. Raster images are commonly used to represent photographs, realistic images, and graphics that have complex color variations and textures.
Key characteristics of raster images include:
- Pixel-Based: Raster images are made up of a fixed number of pixels, and each pixel is assigned a color value. The resolution of a raster image is determined by the number of pixels it contains.
- Resolution: Raster images have a specific resolution, which is defined by the number of pixels per inch (PPI) or dots per inch (DPI). Higher resolutions result in more detail and sharpness.
- File Formats: Common raster image file formats include JPEG, PNG, GIF, BMP, and TIFF. Each format has its own features and advantages, such as support for transparency (PNG), animation (GIF), and lossy compression (JPEG).
- Image Quality: Raster images can suffer from pixelation if they are enlarged beyond their original resolution. Enlarging a raster image can cause individual pixels to become visible, resulting in a loss of quality.
- File Size: Raster images can have larger file sizes, especially if they have high resolutions. This is because each pixel in the image requires storage.
- Editing Limitations: Raster images can be edited to some extent, but excessive manipulation or resizing can lead to a loss of image quality. Editing can also introduce artifacts or visual anomalies.
Raster images are well-suited for photographs, scanned images, and complex scenes that require realistic depiction. However, they may not be ideal for images that need to be scaled to different sizes without loss of quality, such as logos and graphics for print materials.
It’s important to choose the appropriate image format and resolution based on the intended use of the image. For instance, high-resolution images are suitable for printing, while lower-resolution images are suitable for online display to reduce loading times.