File formats, compression, and resolution

File Formats

Raster graphics are composed of individual pixels, with each pixel holding colour information. Examples of raster graphics file formats include JPEG, PNG, BMP, and GIF.
Vector graphics are mathematically derived and can be scaled without loss of quality. Common vector formats include SVG, AI, EPS, and PDF.
JPEG (Joint Photographic Experts Group) is widely used for photographs due to its ability to display millions of colours, but it uses lossy compression which can result in artefacts if the image is edited repeatedly.
PNG (Portable Network Graphics) supports lossless compression, preserving image quality. It can handle high-resolution images and supports transparency.
GIF (Graphics Interchange Format) is used for small, simple graphics and animations. It uses lossy compression and supports a palette of only 256 colours.
PDF (Portable Document Format) is universally accessible and retains the formatting of the original document. A PDF can contain vector graphics, raster images, and text, making it versatile.

Compression

Lossy compression reduces file size by discarding some image data. The lost information is irreversible and can result in lower quality images over time (a phenomenon known as ‘generation loss’).
Lossless compression reduces file size without losing any image quality, as the image can be fully restored. This level of compression is less effective in reducing file size compared to lossy compression.

Resolution

Image resolution refers to the level of detailing in an image and is typically measured in pixels per inch (PPI). The higher the PPI, the higher the image resolution, and subsequently the image’s clarity and sharpness.
In printing, resolution is measured in dots per inch (DPI). A higher DPI means a higher quality print.
A high-resolution image contains more pixel data and therefore will require more storage space. Careful consideration needs to be given to balance resolution with file size, especially in graphic design projects.