JPEG Image Compression Standards

The process of reducing the number of bits used to represent a DCT coefficient, introducing loss in the process. It aims to reduce data by discarding less important information.

A matrix used in quantization, consisting of values that determine how much rounding is applied to each DCT coefficient. Higher values result in more significant rounding and thus greater loss.

The higher frequency DCT coefficients are more likely to contain less significant and visually less noticeable information, so quantization rounds them more aggressively.

The process of ordering the DCT coefficients in a specific pattern. It aims to group similar coefficients together, maximizing the efficiency of the run-length coding step.

A compression technique used to represent a series of zeros in the data by storing the number of consecutive zeros followed by a non-zero value.

A compression technique used to code DC coefficients by storing the difference between the current DC coefficient and the previous one.

The final step in JPEG compression, further reducing the encoded data by using the statistical distribution of the data to represent it more efficiently.

A compression technique that utilizes the statistical distribution of data to represent it more efficiently.

JPEG is a standard for compressing digital images. Developed by the Joint Photographic Experts Group, it was formally adopted in 1992.

JPEG uses a lossy compression method, meaning some data is discarded during compression, resulting in a smaller file size but potential image quality loss.

The Discrete Cosine Transform (DCT) is a mathematical process used in JPEG to break down images into frequency components, similar to how sound can be analyzed into different frequencies.

The DCT assumes that image information changes gradually within small areas. This means that similar information is often repeated nearby, leading to 'spatial redundancy'.

Humans are less sensitive to the loss of high-frequency details in images. These details are often removed by JPEG to reduce file size.

Since we see luminance (brightness) better than color (chrominance), JPEG uses a technique called 'chroma subsampling' to reduce color data, further reducing file size.

JPEG breaks down images into 8x8 blocks. DCT is performed on each block, transforming spatial data into frequency components. This blocking can lead to 'blocky' artifacts at high compression.

JPEG compresses images with a process involving color conversion, DCT, quantization (reducing precision of DCT coefficients), data ordering, and entropy coding.

In DPCM, each DC coefficient is represented by a pair: (SIZE, AMPLITUDE) where SIZE indicates the number of bits needed to represent the coefficient, and AMPLITUDE contains the actual bit values.

The number of bits required to represent a DPCM coefficient (SIZE) is Huffman coded, as smaller sizes occur more frequently. This increases compression efficiency.

The actual value of the DPCM coefficient (AMPLITUDE) is not Huffman coded. This is because its value can vary greatly, and Huffman coding wouldn't offer significant benefits in this case.

JPEG's default mode, which encodes a grayscale or color image component in a single, sequential scan from left to right, top to bottom.

A JPEG mode that allows progressively building an image by encoding only the most significant information initially, and then refining the details gradually. This results in faster low-quality previews.

One method in progressive JPEG encoding where the DCT coefficients are scanned in order of importance, starting with the DC coefficient and few initial AC coefficients, then gradually adding more AC coefficients.

Another method in progressive JPEG encoding where all DCT coefficients are encoded simultaneously, but with the most significant bits first, followed by less significant bits. This allows for gradual refinement of the image detail.

The JPEG bitstream contains different components like the quantized DCT coefficients, Huffman tables, and marker segments. These components are arranged in a specific order, allowing for efficient decoding.