WebP to JPG or PNG

WebP (pronounced: weppy) is a picture file format that provides both lossy compression and lossless compression (reversible compression). It is derived from the image encoding format VP8. It is considered a sister project of the WebM multimedia format. It was developed by Google after purchasing On2 Technologies and released under BSD license terms.
WebP was originally released in 2010. The goal is to reduce the file size, but to achieve the same picture quality as the JPEG format, hoping to reduce the sending time of picture files on the network. On November 8, 2011, Google began to let WebP support lossless compression and transparent color (alpha channel) functions, and the reference implementation on August 16, 2012 was libwebp officially supported by 0.2.0. According to Google's earlier tests, the lossless compression ratio of WebP's PNG files found on the network is less than 45% of the file size. Even if these PNG files are processed with pngcrush and PNGOUT, WebP can still reduce the file size by 28%. The maximum number of pixels supported by
WebP is 16383x 16383. Lossy compressed WebP only supports 8-bit YUV 4:2:0 format. The lossless compression (reversible compression) WebP supports VP8L encoding and 8-bit ARGB color space. Whether it is lossy or lossless compression, it supports Alpha transparent channel, ICC color configuration, and XMP interpretation data.
WebP has static and dynamic modes. Dynamic WebP(Animated WebP) supports lossy and lossless compression, ICC color configuration, XMP interpretation data, and Alpha transparent channels.

technology

The lossy compression algorithm of WebP is based on intra-frame encoding in VP8 video format and uses RIFF as the container format. Therefore, it is a block-based conversion scheme with an eight-bit color depth and a luma-chroma model (YCbCr4:2:0) with chroma subsampling at a ratio of 1:2. Without content, the RIFF container requires only 20 bytes of overhead and can still store additional metadata (metadata). The side length of the WebP image is limited to 16383 pixels.
WebP is based on block prediction. Each block is predicted based on the values of the three blocks above it and the value of the one block to the left (block decoding is done in raster scan order: from left to right, from top to bottom). There are four basic modes of block prediction: horizontal, vertical, DC (monochrome) and TrueMotion. Data and unpredicted blocks of predicted errors are compressed in 4 × 4 pixel subblocks using discrete cosine transform or Walsh-Adama transform. Both conversions are done using fixed-point arithmetic to avoid rounding errors. The output is compressed using entropy coding. WebP also explicitly supports parallel decoding. The
reference implementation includes a converter for Linux command line programs and a library for decoding, which is the same as WebM. The open source community soon managed to port the converter to other platforms, such as Windows.
WebP's lossless compression uses advanced technologies, such as dedicated entropy codes for different color channels, 2D positions with reverse reference distances and color caches for most recently used colors. This complements basic techniques such as dictionary coding, Huffman coding and color index transformation.

support

Among the current web browsers, Google Chrome and Opera natively support static and dynamic WebP formats, while Google Chrome has supported progressive decoding of WebP since version 12. In addition, all browsers that can play WebM images natively can also display WebP images through javascript. The Pale Moon 26 browser only supports static WebP images. Firefox browsers also support WebP images in version 65.0.
web browsers GNOME Web and KDE picture browsers Gwenview also support WebP. Among
image software, Picasa (from version 3.9), PhotoLine, Pixelmator, ImageMagick, XnView, IrfanView, GDAL, Aseprite and GIMP (from 2.10) all support WebP format natively.
Apple added WebP support in the early beta versions of macOS Sierra and iOS 10. However, WebP support was removed from the iOS 10 and macOS Sierra GM seed versions released on September 7, 2016.

Review

Jason Garrett-Glaser, one of the developers of
x264, made several comments on WebP. According to the test results with other encoders (JPEG, x264, Theora), he thinks that the image quality of WebP is the worst, mostly in terms of ambiguity. He also commented that Google should wait until WebP can surpass JPEG before publishing. However, on April 20, 2011, he mentioned that the new WebP encoder performed very well, surpassing JPEG is just around the corner.

Overview Definition

The new generation of picture format launched by Google in 2010 is superior to the current JPEG format in terms of compression.
Google said, the main advantage of webp is its high efficiency. They found that "with the same quality, the volume of WebP format images is 40% smaller than that of JPEG format images. Google browser already supports webp format, and Opera has also added support after version number Opera11.10. However, Firefox and ie do not support webp format for the time being. flash plug-in can be used to display webp, which will consume some performance.
, the only fly in the ointment is that the encoding time of WebP format images is "8 times longer than that of JPEG format images".
analysts believe that although the WebP format has not been widely supported by various software and hardware like the JPEG format, Google's advantage in promoting this format lies in Chrome browser. The browser developed by Google has a market share of more than 50%.