jpg(jpeg)
jpeg (Joint Photographic Experts Group) is a lossy compression common image format. At the same time it is used to remove redundant image and color data, access was extremely high compression ratio can show very rich and vivid images. 8.3 naming convention but DOS, Windows 95 and other early systems used only to support the extension of up to three characters, for compatibility using .jpg.
png
png is a lossless compression image format
When the original picture data is encoded into png format, can be completely reduced to the original picture data, and encoded into a portion jpeg picture data loss occurs, because different encoding and positioning of both. jpeg focuses on the human eye's perception, brightness retain more information, get rid of some of the information does not affect the perception of color, and therefore is a lossy compression. png is retained all the color information of the original, and the support / alpha channel, and then encoded using lossless compression.
So for jpeg, it is usually for richer colors, you can remove the color picture data redundancy in the case of the human eye can not identify as much as possible; and the need to preserve the original picture png for information needed to support the transparency of the picture.
png to save the image in many different pixel depth and pixel formats to choose from.
png-32:
The depth of each pixel is 32bits, wherein four RGBA channels each accounted 8bits. A so-called four channel RGBA is red, green, blue, transparent color value of each of the four sizes are expressed by 8bits.
png-24:
PNG-24 pixel depth of 24bits, wherein RGB three channels each accounted 8bits. PNG-24 because there is no Alpha channel (transparency channel), so I do not support transparent pictures
png-8:
PNG-8 used in the image of each color are stored in an array of length 255, the call bar color wheel, and then the color corresponding to each pixel storage location in the color bar on the disc. Because the upper limit of 255 kinds of colors, each pixel can represent only 8bits corresponding to the color information. This representation is called the color index colors manner. In contrast PNG-8 does use less space to store the color, but the kind of color that he can say is there is an upper limit, it is converted into PNG-8 will be in place when some color transition in the PNG-32 clearly see not smooth gradients.
webp
The WebP, for simultaneously providing a lossy compression to lossless compression, the image encoding format is derived from VP8.
Webp, it is Google's new imaging technology that allows web drawing, efficient compression without compromising picture format compatible with the actual definition, then let the whole web page download speed.
Due to the current data transmission over the Internet, 65% of all images, WebP is for the purpose of reducing the amount of data transmitted over the network and accelerate development. In order to improve the JPEG image compression format, they use based on VP8 encoding picture compressor, the use of predictive coding technique, while also using a very lightweight based on the RIFF container. This container will increase to 20 bytes per picture, but they want to make pictures of saving storage of metadata
The same as JPEG, WebP is a lossy compression technique using predictive coding. The main advantage of this format is that high efficiency. They found that "the situation in the same quality, size than the JPEG image format WebP image of a small 40%.
The only drawback is the time WebP encoding format of the image 'of 8 times longer JPEG images' ratio
WebP from Google's open source video format WebM