pátek 17. března 2017

Guetzli: Perceptually Guided JPEG Encoder


Guetzli: Perceptually Guided JPEG Encoder
J. Alakuijala, R. Obryk∗ , O. Stoliarchuk, Z. Szabadka, L. Vandevenne, and J. Wassenberg
Google Research Europe
March 14, 2017

Guetzli is a new JPEG encoder that aims to produce visually indistinguishable images at a lower bit-rate than other common JPEG encoders. It optimizes both the JPEG global quantization tables and the DCT coefficient values in each JPEG block using a closed-loop optimizer. Guetzli uses Butteraugli [1], our perceptual distance metric, as the source of feedback in its optimization process. We reach a 29-45% reduction in data size for a given perceptual distance, according to Butteraugli, in comparison to other compressors we tried. Guetzli’s computation is currently extremely slow, which limits its applicability to compressing static content and serving as a proof- of-concept that we can achieve significant reductions in size by combining advanced psychovisual models with lossy compression techniques

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