https://github.com/google/knusperli

A deblocking JPEG decoder
https://github.com/google/knusperli

Last synced: 28 days ago
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A deblocking JPEG decoder

• Host: GitHub
• URL: https://github.com/google/knusperli
• Owner: google
• License: apache-2.0
• Created: 2018-03-08T10:06:34.000Z (almost 7 years ago)
• Default Branch: master
• Last Pushed: 2023-09-10T02:05:58.000Z (over 1 year ago)
• Last Synced: 2024-08-04T02:10:44.975Z (4 months ago)
• Language: C++
• Homepage:
• Size: 1.55 MB
• Stars: 467
• Watchers: 20
• Forks: 27
• Open Issues: 10
• Metadata Files:
  • Readme: README.md
  • Contributing: CONTRIBUTING.md
  • License: LICENSE

Awesome Lists containing this project

• AwesomeCppGameDev - knusperli

README

        
# Knusperli

The goal of Knusperli is to reduce blocking artifacts in decoded JPEG images, by

interpreting quantized DCT coefficients in the image data as an interval, rather

than a fixed value, and choosing the value from that interval that minimizes

discontinuities at block boundaries.

a traditional JPEG decoder (Imagemagick 7.0.8-59) | Knusperli

--------------------------------------------------|-----------------------------------------------

![baboon JPEG, zoomed][baboon-jpeg-crop]          | ![baboon Knusperli, zoomed][baboon-knus-crop]

![baboon JPEG][baboon-jpeg]                       | ![baboon Knusperli][baboon-knus]

## Building

Knusperli builds with [Bazel][bazel]:

    CC=gcc bazel build :knusperli

    bazel-bin/knusperli input.jpg output.png

## Details

A JPEG encoder quantizes DCT coefficients by rounding coefficients to the

nearest multiple of the elements of the quantization matrix. For every

coefficient, there is an interval of values that would round to the same

multiple. A traditional decoder uses the center of this interval to reconstruct

the image. Knusperli instead chooses the value in the interval that reduces

discontinuities at block boundaries. The coefficients that Knusperli uses, would

have rounded to the same values that are stored in the JPEG image.

## Disclaimer

This is not an officially supported Google product.

[bazel]: https://bazel.build/

[baboon-jpeg-crop]: doc/img/baboon.q50.jpeg.crop.png

[baboon-knus-crop]: doc/img/baboon.q50.knusperli.crop.png

[baboon-jpeg]: doc/img/baboon.q50.jpeg.png

[baboon-knus]: doc/img/baboon.q50.knusperli.png