What technique is used by JPEGs for compression?

• A. ZIP
• B. DCT
• C. TCD
• D. TIFF-8

Answer: (B)

The technique used by JPEG for compression is the Discrete Cosine Transform (DCT). JPEG breaks the image into small blocks (typically 8x8), then applies DCT to each block to convert the spatial pixel values into frequency components. This shows most of the image's information in a few low-frequency coefficients, while high-frequency components (often less visually important) are quantized more aggressively, reducing precision and achieving compression. The remaining data is then encoded efficiently with entropy coding. This combination—transform to frequency domain via DCT, then quantize and entropy-encode—gives JPEG its effective lossy compression. The other options don’t describe JPEG’s core compression method: ZIP is a general lossless compressor, TCD isn’t a standard image compression technique, and TIFF-8 refers to a format/depth, not the compression method used by JPEG.