![]() ![]() DCT stand for Discrete cosine transformation. Frequency block can be quantized to produce zero coefficients as much as possible. Show me 8 coefficients AC DC 8 coefficients An 8x8 Block in the Frequency DomainĢ2 JPEG - DCT DCT is reversible function:ĭCT(X) = IDCT(DCT(X)) DCT Convert RGB Block to Frequency Domain Block. Each type have a coding algorithm in the jpeg encoding process. AC coefficients is the rest 63 coefficients in the Block. IDCT Dequantize 8x8 block in Frequency DomainĢ2 1376 -12 72 -17 IDCT Dequantize 8x8 block in Frequency Domain Frequency Domainġ9 JPEG - Decoding e.g. Dequantize Quantized 8x8 Block Frequency Domainġ7 JPEG - Decoding – e.g. Quantize Quantized 8x8 Block Frequency Domain 2Ģ 86 -1 6 Quantized 8x8 Block Frequency Domainġ6 JPEG - Decoding – e.g. DCT Quantize 8x8 block in Frequency Domain Table HC Table JPEG File DATA Encoding Process Decoding Processġ0 JPEG - Encoding Quality Table DCT Quantize 8x8 block 8x8 blockġ1 JPEG - Decoding Quality Table IDCT Dequantize 8x8 block 8x8 blockġ2 JPEG - Encoding e.g. RGB Image Data RGB Image Data Quantization Table DCT Quantize Dequantize IDCT H.C. RGB Image Data ( a Matrix of size NxMx3 ) DCT/IDCT Lossless Two Dimension Discrete Cosine Transformation Quantize/Dequantize Division By a user define Quality table then integer roundation Lossy Source Coding/Decoding Huffman coding or arithmetic coding Lossless Contain Header, Quantization Tables, Source Coding Tables, and Data. It obtained excellent quality for high compression rates. tiff file extensions 24-bit colors JPEG is lossy and lossless. ![]() ![]() Although it is a lossy compression technique, it yields an excellent quality image with high compression rates. JPEG stands for Joint Photographic Experts Group JPEG compression is used with. OutGuess can’t be detected by visual attacks. OutGuess distribute the message bits randomly by using a user password as a seed to a Random Generator. Vulnerable to statistical attacks also.į5 distribute the message bits randomly by using a user password as a seed to a Random Generator. JSteg sequentially embeds the hidden data in LSBs of quantized DCT coefficients. Steganography Watermarking Cryptography Video Image Audio BMP GIF JPEG PNG TIF Subject Pyramid Future workģ Research Hierarchy Information Hiding Existing Hiding Content Hiding How to recover original image? 2 Proposed new F5 attacks. 2 Agenda Research Hierarchy Related Work. ![]()
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