What jpg files usually are

jpg files are image files. jpg is a compression standard for continuous-tone still images. It mainly uses a joint coding method of predictive coding, discrete cosine transform and entropy coding to remove redundant images and color data. It is a lossy compression format, which can Image compression requires a small storage space and will cause damage to image data to a certain extent.

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JPG files generally refer to JPEG format.

JPEG (Joint Photographic Experts Group) is the product of the JPEG standard, which was formulated by the International Organization for Standardization (ISO) and is a compression standard for continuous-tone still images. JPEG format is the most commonly used image file format, with the suffix .jpg or .jpeg.

JPEG (Joint Photographic Experts Group) is a standard for continuous-tone static image compression. The file suffix is ​​.jpg or .jpeg, which is the most commonly used image file format. It mainly uses a joint coding method of predictive coding (DPCM), discrete cosine transform (DCT) and entropy coding to remove redundant images and color data. It is a lossy compression format, which can compress images in a small storage space. Space will cause damage to image data to a certain extent. In particular, using an excessively high compression ratio will reduce the quality of the image recovered after final decompression. If you pursue high-quality images, it is not advisable to use an excessively high compression ratio.

However, JPEG compression technology is very advanced. It can use lossy compression to remove redundant image data. In other words, you can get better image quality using less disk space. Moreover, JPEG is a very flexible format that has the function of adjusting image quality. It allows files to be compressed with different compression ratios and supports multiple compression levels. The compression ratio is usually between 10;1 and 40;1. The higher the compression ratio, the higher the compression ratio. The larger the compression ratio, the lower the image quality; conversely, the smaller the compression ratio, the higher the image quality. For the same image, files stored in JPEG format are 1/10~1/20 of other types of files, usually only a few tens of KB, and the quality loss is small and basically invisible. The JPEG format mainly compresses high-frequency information, retains color information well, and is suitable for use on the Internet; it can reduce the transmission time of images and supports 24-bit true color; it is also commonly used in images that require continuous tone.

JPEG format can be divided into three formats: standard JPEG, progressive JPEG and JPEG2000.

1. Standard JPEG format; this type can only display images from top to bottom when downloading a web page. Only when all image data is downloaded can the full image be seen.

2. Progressive JPEG; when downloading a web page, this type first presents a rough appearance of the image, and then slowly presents the complete content, and documents saved in the progressive JPG format are faster than files saved in the progressive JPG format. Documents in the standard JPG format are smaller, so if you want to use images on a web page, you can use this format more often.

3. JPEG2000; it is a new generation of image compression method with higher compression quality. It can improve the mosaic phenomenon and positional disorder caused by signal instability during wireless transmission, and improve the quality of transmission. .

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