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How to understand the PNG picture format, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

I. brief introduction

The organization format of PNG pictures is made up of many data blocks, each of which represents different information about the image. Except for the png header, each data block is organized according to the structure of data length + data identifier + CRC check code. As shown below:

II. Major PNG data blocks

The header letter of a PNG picture takes 8 bytes to uniquely identify the type of image.

two。 The header identification is followed by a data segment called IHDR, which contains information about the height, width, bit depth of the image.

3. IDAT is the main compressed data information in PNG, and its structure is as shown in the figure:

4. At the end of the file, there is a sign of the end of the file, which is also organized according to the organizational format of the data segment, but the data length is 0.

III. Location requirements for major data blocks

Of course, different data blocks have certain location and requirement restrictions when PNG files are stored and organized, as shown in the following figure.

Conclusion

Of course, PNG has some other data segments, but it is still organized in a similar way. And PNG images generated by different operating systems, tools, or platforms may not be organized in exactly the same format. But catch the most critical IHDR, IDAT and the beginning and end identifiers of the file, and others are similar.

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