iShrinker is a helper that, thanks to Guetzli algorithm, enables users to reduce images online by uploading them to its website. The reduced output is a JPEG image sent automatically via e-mail. Guetzli [guɛtsli] — cookie in Swiss German — 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, a perceptual distance metric, as the source of feedback in its optimization process. It reaches a 29-45% reduction in data size for a given perceptual distance.
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Learn more about Guetzli here.