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JPEG Compression in Matlab by Michael Christensen

Learn about JPEG compression, including motivation, general methods, step-by-step instructions, and example codes. Explore shifting, Discrete Cosine Transform, quantization processes, and file conversion. Discover how to input multiple file types, adjust quantization matrix, and convert JPEG files back to uncompressed format.

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JPEG Compression in Matlab by Michael Christensen

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  1. JPEG Compression in Matlab Michael Christensen

  2. Outline • Motivation • General Method • Still to do…

  3. Motivation • Instruction • Provide a simple example

  4. Method Step 1 Shift by 27

  5. Method, Cont. Step 2 2D Discrete Cosine Transform

  6. Method, Cont. . / Step 3 Quantization

  7. Method, Cont. ( ) = −26, −3, 0, −3, −3, −6, 2, −4, 1, −4, 1, 1, 5, 1, 2, −1, 1, −1, 2, 0, 0, 0, 0, 0, −1, −1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

  8. Method, Cont. ( ) −26, −3, 0, −3, −3, −6, 2, −4, 1, −4, 1, 1, 5, 1, 2, −1, 1, −1, 2, 0, 0, 0, 0, 0, −1, −1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 Shorten = = −26, −3, 0, −3, −3, −6, 2, −4, 1, −4, 1, 1, 5, 1, 2, −1, 1, −1, 2, 0, 0, 0, 0, 0, −1, −1, EOB 101001110011101111110111010110101011101000011001101110101110101010101101011011101011011110110111010001101110001101111011011000110101010111011101001101111010111011000110011110111010101100110101101110101010011110101110101010

  9. Method, Final File Headers, etc. 101001110011101111110111010110101011101000011001101110101110101010101101011011101011011110110111010001101110001101111011011000110101010111011101001101111010111011000110011110111010101100110101101110101010011110101110101010 + = Output File

  10. Still To Do… • Input multiple file types • Modifiable quantization matrix for variable compression rates • JPEG file conversion back to uncompressed format

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