General Block Diagram of Image
Compression
Image compression can be categorized in the following two categories.
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Lossy Compression
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Lossless Compression
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Lossy compression technique of
image compression involves eliminating redundant information in an image.
During reconstruction of the original image this redundant information cannot
be recovered. Such a method is used in applications where minor loss of fidelity
is acceptable in order to achieve a substantial reduction in the overall size
of the image and thereby reduction in the bit rate.
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Lossless compression technique of
image compression involves reconstructing the original image by recovering
every single bit. Such a method is used in applications where even a minor
loss of data is not acceptable.
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Lossy compression is a popular method
because it reduces the size of the file and thereby facilitates in file
storage. An application of Lossy Compression is for storing photographs for
personal use.
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Lossless compression is preferred
for archival purposes and often for medical imaging, technical drawings,
which requires higher level of precision
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Methods for Lossy Compression:
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Chroma
sub sampling
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Transform
coding
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Quantization
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Methods for Lossless Compression:
·
Run-length
encoding
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DPCM and Predictive
Coding
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Entropy
encoding
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Formats of Lossy Compression:
TIFF, MNG, JPEG
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Formats of Lossless Compression:
PNG, GIF, RAW
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