1. D10K-6C01 Pengolahan Citra PCD-08 Image Compression Program Studi S-1 Teknik Informatika FMIPA Universitas Padjadjaran Semester Genap 2015-2016

2. PCD-07 Algoritma Pengolahan Citra 4 Image Compression Overview Images take a lot of storage space – 1024 x 1024 x 32 x bits images requires 4 MB – suppose you have some video that is 640 x 480 x 24 bits x 30 frames per second, 1 minute of video would require 1.54 GB Many bytes take a long time to transfer slow connections – suppose we have 56,000 bps – 4MB will take almost 10 minutes – 1.54 GB will take almost 66 hours

3. PCD-07 Algoritma Pengolahan Citra 4 Research Opportunity Storage problems the desire to exchange images over the Internet have lead to a large interest research in image compression algorithms.

4. PCD-07 Algoritma Pengolahan Citra 4 Goal of Image Compression The goal of image compression is to reduce the amount of data required to represent a digital image.

5. PCD-07 Algoritma Pengolahan Citra 4 Approaches Lossless – Information preserving – Low compression ratios Lossy – Not information preserving – High compression ratios Trade-off: image quality vs compression ratio

6. PCD-07 Algoritma Pengolahan Citra 4 Data ≠ Information Data and information are not synonymous terms! Data is the means by which information is conveyed. Data compression aims to reduce the amount of data required to represent a given quantity of information while preserving as much information as possible.

7. PCD-07 Algoritma Pengolahan Citra 4 Example: Data and Information The same amount of information can be represented by various amount of data Examples – Your wife, Helen, will meet you at Logan Airport in Boston at 5 minutes past 6:00 pm tomorrow night – Your wife will meet you at Logan Airport at 5 minutes past 6:00 pm tomorrow night – Helen will meet you at Logan at 6:00 pm tomorrow night

8. PCD-07 Algoritma Pengolahan Citra 4 Compression Ratio compression Compression ratio:

9. PCD-07 Algoritma Pengolahan Citra 4 Example

10. PCD-07 Algoritma Pengolahan Citra 4 Flow of Image Compression The image file is converted into a series of binary data, which is called the bit-stream The decoder receives the encoded bit-stream and decodes it to reconstruct the image The total data quantity of the bit-stream is less than the total data quantity of the original image

11. IMAGE COMPRESSION REVISITED

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17. Measuring Performance Compression Ratio: Root Mean square error: Peak signal to noise ratio: Setiawan HadiPengolahan Citra Dijital17

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33. ILUSTRASI JPEG Setiawan HadiPengolahan Citra Dijital33 Q=100%Q=50%Q=25% Q=10%Q=1%

34. Tabel Komparasi Q%Q%SIZECRCOMMENTS 100 83,2612.6:1Extremely minor artifacts 50 15,13815:1Initial signs of subimage artifacts 25 9,55323:1 Stronger artifacts; loss of high resolution information 10 4,78746:1 Severe high frequency loss; artifacts on subimage boundaries ("macroblocking") are obvious 1 1,523144:1 Extreme loss of color and detail; the leaves are nearly unrecognizable Setiawan HadiPengolahan Citra Dijital34