* High-Frequency Detail: This is the most significant loss. JPEG excels at discarding subtle details like fine textures, sharp edges, and intricate patterns. This is because high-frequency information (rapid changes in color and brightness) is deemed less visually important by the algorithm.
* Color Information: JPEG can reduce the color resolution of the image. This means that the image will have fewer distinct colors, which can lead to color banding or posterization, especially in areas with smooth color gradients.
* Sharpness: Edges and lines become softer and less defined.
* Fine Texture: Details in textured areas (like grass, fabric, or skin) get smoothed out or blended together.
* Potential Artifacts:
* Blocking: Visible square blocks or tiles appear in the image, especially in areas with high compression.
* Ringing (Gibbs phenomenon): Halo-like artifacts appear around sharp edges.
* Color Bleeding: Colors smear into adjacent areas, often noticeable around high-contrast regions.
* Ability to Revert to the Original: Lossy compression means that the information removed during compression cannot be perfectly recovered. Each time you save a JPEG image, it's compressed again, leading to further loss of quality.
In summary, JPEG compression trades image quality for smaller file size. The level of loss depends on the compression ratio used. Higher compression ratios result in smaller files but more noticeable loss of detail and artifacts.