Nathan Willis investigates Linux tools for using the WebP image format
over at Linux.com. WebP
is a lossy image format (like JPEG) that was introduced by Google
back in September. "WebP compression is essentially an adaption of a single frame of WebM video. It, too, breaks the image into blocks (although 4-by-4 in size, rather than 8-by-8), but in place of JPEG's DCT [Discrete Cosine Transform] and high-frequency bit-chopping step, it uses the intra-frame coding algorithm from WebM. Intra-frame coding is the coding down within a single frame, as opposed to between two consecutive frames, and WebM's method involved constructing a prediction for each block based on the blocks adjacent to it. The encoder saves the predictions and the differences between the predictions and the real input blocks in the output file — if prediction is going well, as it should for most continuous-tone images like photos, the output is smaller than the raw input — and the result compressed with lossless techniques.
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