JPEG DCT coefficients access in C

This provides access via an array to the DCT coefficients which can then be modified before being re-saved as another JPEG. It depends on the IJG JPEG library (or libjpeg) which can be found here: http://www.ijg.org/

Origin:

[211044]

./jpegquant -q 2 lena.q100.jpg lena.q100.jq02.jpg 

[175851]

butteraugli: 0.776085

jpeg-compare -m sum -n lena.q100.jpg lena.q100.jq02.jpg SUM: 0.945429 (UM) # > 0.93 (HIGH)

./jpegquant -q 4 lena.q100.jpg lena.q100.jq04.jpg 

[127572]

butteraugli: 1.300308

jpeg-compare -m sum -n lena.q100.jpg lena.q100.jq04.jpg SUM: 0.833405 (UM) # > 0.76 (MEDIUM)

./jpegquant -q 10 lena.q100.jpg lena.q100.jq10.jpg 

[60209]

butteraugli: 2.399572

jpeg-compare -m sum -n lena.q100.jpg lena.q100.jq10.jpg SUM: 0.574876 (UM) # > 0.50 (LOW)

./jpegquant -q 20 lena.q100.jpg lena.q100.jq20.jpg 

[30029]

butteraugli: 4.421662

jpeg-compare -m sum -n lena.q100.jpg lena.q100.jq20.jpg SUM: 0.367628 (UM) # < 0.50 (DIRTY)

See all sample files for JPEGquant.

• https://github.com/kud/jpegrescan
• https://github.com/ImageProcessing-ElectronicPublications/jpeg-recompress

Copyright (C) 2012, Owen Campbell-Moore.
Modify 2019-2023, zvezdochiot
Public Domain Mark 1.0

https://github.com/ImageProcessing-ElectronicPublications/jpegquant