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What are the benefits of using PNG format

2025-01-18 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Development >

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This article shares with you about the benefits of using the PNG format. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

BMP is a hardware-independent image file format, which is widely used. It uses the bit mapping storage format and does not use any compression except for the optional depth of the image, so the BblP file takes up a lot of space. The image depth of BMP files can be selected from lbit, 4bit, 8bit and 24bit. When BMP files store data, images are scanned from left to right and from bottom to top.

Because BMP file format is a standard for exchanging graph-related data in Windows environment, the graphics and image software running in Windows environment supports BMP image format.

A typical BMP image file consists of three parts: the bitmap header data structure, which contains the type and display content of the BMP image file, and the bitmap information data structure, which contains the width, height, compression method and color definition of the BMP image.

JPEG compression technology can be said to be the basis of all image compression technologies. It is suitable for still image compression, directly deal with the whole picture, compression ratio of 20-80 times, there is no choice of resolution. Therefore, it is necessary to wait until the entire compressed file transfer is completed before it is decompressed into an image, which takes tens of seconds or even minutes to transmit a high-resolution picture.

MJPEG (Motion JPEG) is a dynamic image compression technology developed on the basis of JPEG. It only compresses a single frame without considering the changes between different frames in the video stream. The high definition video image can be obtained, and the video definition and the number of compressed frames of each channel can be set flexibly. The compressed picture can also be edited arbitrarily. But its defects are also very obvious, one: serious frame loss and poor real-time performance, under the premise that each road must be high-definition, it is difficult to complete real-time compression. Second, the compression efficiency is low and the storage space is large.

Later, there is a multi-layer JPEG (ML-JPEG) compression technology, which adopts gradual technology, which first transmits low-resolution images, and then sends more detailed compressed data, so as to improve the picture quality. Although the time required for this approach is the same as before. However, because you can see the picture first, users will think that this way is better.

PNG is an image file storage format developed in the mid-1990s in an attempt to replace GIF and TIFF file formats while adding some features that the GIF file format does not have. The streaming Network Graphics format (Portable Network Graphic Format,PNG) name comes from the unofficial "PNG's Not GIF", which is a bitmap file (bitmap file) storage format that is read as "ping". When PNG is used to store grayscale images, the depth of grayscale images can be up to 16 bits, and when storing color images, the depth of color images can be up to 48 bits, and up to 16 bits of α-channel data can be stored. PNG uses a lossless data compression algorithm derived from LZ77.

The PNG file format retains the following features of the GIF file format:

Using a color lookup table, or a color palette, can support color images in 256 colors.

Streaming read / write performance (streamability): the image file format allows continuous reading and writing of image data, which is ideal for generating and displaying images during communication.

Successive approximation display (progressive display): this feature enables the image to be displayed on the terminal while the image file is transmitted on the communication link, and the details of the image are gradually displayed after the whole outline is displayed, that is, the image is displayed with low resolution at first, and then its resolution is gradually improved.

Transparency (transparency): this feature prevents certain parts of the image from being displayed and is used to create distinctive images.

Auxiliary information (ancillary information): this feature can be used to store some text comment information in an image file.

Independent of the computer software and hardware environment.

Use lossless compression.

Add features to the PNG file format that are not available in the following GIF file formats:

Each pixel is a 48-bit true color image.

Each pixel is a 16-bit grayscale image.

Alpha channels can be added to grayscale and true color images.

Add the gamma information of the image.

Use cyclic redundancy codes (cyclic redundancy code,CRC) to detect damaged files.

Speed up the successive approach display mode of image display.

Standard read / write kit.

Multiple images can be stored in one file.

File structure

PNG image format files, or data streams, consist of an 8-byte PNG file signature (PNG file signature) field and more than three data blocks (chunk) organized according to a specific structure.

PNG defines two types of data blocks, one is called critical data block (critical chunk), which is a standard data block, and the other is called auxiliary data block (ancillary chunks), which is an optional data block. Critical data blocks define four standard data blocks, which must be contained in each PNG file, and must be supported by PNG reader software. Although the PNG file specification does not require PNG codecs to encode and decode optional data blocks, the specification advocates support for optional data blocks.

GIF (Graphics Interchange Format), the original meaning of "image interchange format", is an image file format developed by CompuServe in 1987. The data of GIF file is a lossless compression format of continuous tone based on LZW algorithm. Its compression ratio is generally about 50%, and it does not belong to any application. At present, almost all related software supports it, and a large number of software in the public domain are using GIF image files. The data of GIF image file is compressed, and the compression algorithm such as variable length is adopted. Therefore, the image depth of GIF ranges from lbit to 8bit, that is, GIF supports up to 256 colors. Another feature of GIF format is that it can store multiple color images in a GIF file. If multiple image data stored in a file are read out and displayed on the screen one by one, it can constitute the simplest animation.

GIF is divided into static GIF and animation GIF, supporting transparent background images, suitable for a variety of operating systems, "body size" is very small, many small animations on the Internet are in GIF format. In fact, GIF is to save multiple images as an image file to form animation, so in the final analysis, GIF is still a picture file format.

Thank you for reading! This is the end of this article on "what are the benefits of using PNG format?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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