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To my eye, webp reduces compression artifacts at the expense of losing detail (this is especially visible in the portrait example). Another way to accomplish a
by bstrong 16y ago
To my eye, webp reduces compression artifacts at the expense of losing detail (this is especially visible in the portrait example).
Another way to accomplish a similar effect without requiring a new file format would be to apply a selective gaussian blur (or another de-artifacting filter) to highly compressed jpegs before displaying them.
Of course, no one does that because the trade-off is generally not considered to be a good one.
- chc 16y agoCompression artifacts are loss of detail. Applying any kind of blur filter to an image that had compression artifacts would result in more loss of detail (and applying it strongly enough to remove the artifacts would pretty much obliterate any recognizable details).
- astrange 16y agoCompression artifacts add noise via coefficient rounding, just like audio codecs add noise instead of "removing sound you can't hear". However, encoders with poor psy-optimization (i.e. not x264) usually choose blurry quantizations that don't add much noise but also remove the original detail. Also, the deblocking filter in VP8/H264 is nothing but a selectively applied blur that hides previous compression steps. It works pretty well.
- bstrong 16y agoActually, while applying a blur does obviously eliminate detail, you can retain most of the important detail with a selective blur. Give it a try in gimp and see for yourself. The default selective gaussian settings work pretty well for de-artifacting, and the loss of detail arguably isn't much worse that that in webp compression. Some of the commercial de-artifacting tools use different techniques (I don't know what they are) that result in even less loss of detail.