OutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionJPEG CompressionIan SnyderDecember 11, 2009Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionJPEG Image Compression StandardINeed for a standardIHistory, develpoment and adoption of JPEG’s standardIWidespread useIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionJPEG Image Compression StandardINeed for a standardIHistory, develpoment and adoption of JPEG’s standardIWidespread useIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionJPEG Image Compression StandardINeed for a standardIHistory, develpoment and adoption of JPEG’s standardIWidespread useIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionImage CompressionDefinition: The compression of graphics for storage and/ortransmission.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionCompression MethodsILossless Compression: Compression that does not remove anydata from the original file.ILossy Compression: Compression that deletes information inorder to achieve a better compression ratio.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionCompression MethodsILossless Compression: Compression that does not remove anydata from the original file.ILossy Compression: Compression that deletes information inorder to achieve a better compression ratio.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionBitmap ImagesA bitmap image is represented by an array of bits that correspondto pixel colors.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionImage TypesThere are three general types of bitmap images:IIntensity ImagesIIndexed (256-color) ImagesIRGB (Truecolor) ImagesIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionRGB Example ImageIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionSeal ImageThis is the intensity image that was compressed step by step.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionJPEG Compression StepsIThe Discrete Cosine TransformIQuantizationIReorderingIHuffman CodingIan Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionBlock Division of Image MatrixWhen an image is JPEG compressed, it it first sliced into 8 × 8matrix blocks of pixel entries.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionExample Image MatrixThis is the matrix taken from the top left corner of the ‘Seal’image:O =182 181 176 178 176 177 173 175182 184 177 176 179 174 176 173176 176 176 180 178 174 171 168182 174 176 180 177 169 168 168180 172 181 178 171 170 173 172181 170 171 170 170 178 174 174176 174 170 170 171 182 179 166176 173 170 176 173 181 179 168Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionDiscrete Cosine TransformIThe discrete cosine transform converts an image matrix fromits spatial domain into a frequency domain.IGreater changes in luminosity across the image arerepresented by higher frequencies.IThe greatest frequencies are concentrated in the upper left ofthe matrix.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionDiscrete Cosine TransformIThe discrete cosine transform converts an image matrix fromits spatial domain into a frequency domain.IGreater changes in luminosity across the image arerepresented by higher frequencies.IThe greatest frequencies are concentrated in the upper left ofthe matrix.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionDiscrete Cosine TransformIThe discrete cosine transform converts an image matrix fromits spatial domain into a frequency domain.IGreater changes in luminosity across the image arerepresented by higher frequencies.IThe greatest frequencies are concentrated in the upper left ofthe matrix.Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionDCT EquationCuv= αuαvM−1Xm=0N−1Xn=0Amncosπ(2m + 1)u2Mcosπ(2n + 1)v2N0 ≤ u ≤ M − 1, 0 ≤ v ≤ N − 1Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionDCT Equation Continuedαu=(1/√M, if p = 0,p2/M, if 1 ≤ p ≤ M − 1αv=(1/√M, if p = 0,p2/M, if 1 ≤ p ≤ M − 1Ian Snyder JPEG CompressionOutlineIntroductionImages and CompressionWalkthrough of JPEG Compression StepsComplete Compression ProcessResults and ConclusionDCT MatrixThe previous equation produces this DCT matrix ‘C’:C