Different Modes of JPEG Compression explain with example

Different Modes of JPEG:

The JPEG standard supports numerous modes. Some of the commonly used ones are:
1. Sequential Mode
2. Progressive Mode
3. Hierarchical Mode
4. Lossless Mode

Sequential Mode:

It is the default JPEG mode. Each grey-level image or colour image component is encoded in a single left-to-right, top-to-bottom scan. The “Motion JPEG” video codec uses Baseline Sequential JPEG, applied to each image frame in the video.

Progressive Mode:

The key difference with the sequential mode is that each image component is encoded in multiple scans rather than in a single scan. The first scans encode a rough but recognizable version of the image which can be transmitted quickly. JPEG progressive mode is widely supported in web browsers and it is most useful when the speed of the communication line is low.

Hierarchical Mode:

This mode provides a “pyramidal” or hierarchical encoding of an image at multiple resolutions, each differing in resolution from its adjacent encoding by a factor of two in either the horizontal or vertical dimension or both. The encoded image at the lowest resolution is a compressed low-pass filtered image whereas the image at successively higher resolutions provides additional details.

Lossless Mode:

Lossless JPEG is a very special case of JPEG which indeed has no loss in its image quality. It does not use the DCT-based method. Instead, it employs a simple differential coding method.