SJ 20708-1998 Military pixel digital map file format and encoding SJ20708-1998 standard download decompression password: www.bzxz.net

FL0134 Military Standard of the Electronic Industry of the People's Republic of China
SJ 20708-1998
Format and encoding of military vectorial map1998-03-18 Issued
Implementation on 1998-05-01
Approved by the Ministry of Electronics Industry of the People's Republic of China1
Subject content
Scope of application
Referenced documents
General requirements
Detailed requirements
File structure of pixel digital map
5.2 Map file pixel data description information
Map file comprehensive information
Bitmap array
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Military Standard of the Electronic Industry of the People's Republic of ChinaFormat and encoding of military pixel digital map files 1 Scope
1.1 Subject content
This standard specifies the format and coding of military pixel digital map files. 1.2 Scope of application
SJ 20708—1998
This standard applies to the format and coding of 1:10,000 to 1:1 million military pixel digital map files. Other pixel digital map files can also be used for reference.
2 Referenced documents
GJB873-91 Command Automation Military Map Division and Coding 3 Definitions
This standard adopts the following definitions.
3.t General information for map file Descriptive and management information about a digital map as a whole. 3.2 Bitmap array bitmaparray
A bitmap array is a rectangular data area that records the value of each pixel of the image. 4 General requirements
4.1 The format and coding of military pixel digital map files are pixel digital maps stored in file form, and it is also necessary to facilitate the transmission of pixel digital maps across the network. 4.2 The format and coding of military pixel digital maps should include comprehensive management information of pixel maps and storage methods of pixel data.
4.3 Pixel data is stored in two ways: uncompressed and compressed, so as to facilitate the use, storage and transmission in different occasions.
5 Detailed requirements
The Ministry of Electronics Industry of the People's Republic of China issued on March 18, 1998 and implemented on May 1, 1998
5.1 File structure of pixel digital map
SJ 20708—1998
Pixel digital map files consist of the following three parts: - Map file pixel data description information; - Map file comprehensive information:
Bitmap array.
5.2 Map file pixel data description information
Map file pixel data description information includes image data width, height, color description and other information, as shown in Table 1. Table 1 Map file pixel data description information
Parameter name
bfType【File type）
brsize（File size）
bfReserved1（Reserved word）
bfReserved2《Reserved word》
bfOffBits (Offset>
bisize (size)
biWidth (image width)
biHeighr (image height)
biplanes (bit half plane)
biBirCount (number of pixels)
bicompress
(compression method)
biSizelmage
(number of image nodes)
biXPelsPerMeter
(horizontal spacing)
biYPelsPerMeter||tt| |【Vertical resolution】
Byte length
Refers to the type of map file, must be BM
Refers to the size of the map file
Reserved for future use, here is 0 Reserved word, for future use, here is (Refers to the starting position of the map array data
Refers to the byte size of the description information part, here is 40 In pixels, gives the width of the bitmap array In pixels, gives the height of the bitmap array Indicates the number of bit planes to be changed, must be 1 The number of each pixel, its value must be 1 (10 colors), 4 (16 colors), 8 (256 colors), 24 (1677216 colors) bitmap array The type of lossless compression used, 0: non-compression: 1: 8 bits per pixel compression method: 2: 4 bits per pixel compression method
The number of image nodes
The horizontal resolution of the image given in pixels per meter of the target deviceThe vertical resolution of the image given in pixels per meter of the target deviceiKAoNrKAca
Parameter name
bicirUsed
(number of colors in the color table)
biClrimportont
(vertical index)
bmiC.color(color table)wwW.bzxz.Net
5.2.1 Compression method
Unsigned
Character type
SJ20708—1998
Continued Table 1
Byte length
Description
The number of colors actually used by the image in the palette, this value is between 0 and 256, if it is 0, the number of colors is determined by the value of the biBitCount field: if it is not 0, the color index value actually used by the bitmap array is given, here it is 0
refers to the color in the bitmap array, the next 3 bytes are the red, green, and blue color values: the last byte is 0, when biBitCount=1, 4, 8, bmiColor has 2, 16, and 256 bits respectively, when biBitCount=24, the BmiColor table entry is empty. The storage format of bitmap array data is compressed and uncompressed. 5.2.1.1 Uncompressed format
In the uncompressed format, the pixel value of each point in the bitmap corresponds to a number of bits in the bitmap array, and the size of the bitmap array is determined by the width, height and number of bits per pixel of the image. 5.2.1.1.1 Relationship between bitmap scan line and bitmap array If n words are used to record the pixel value of a scan line, the size of the bitmap array is n*biHeight bytes. At this time, the 0~n-1 words of the bitmap array record the pixel values ​​of the first scan line of the image, and the n~2n-1 bytes record the pixel values ​​of the second scan line of the image. And so on, the (-)*II~1*(μ-1) bytes of the bitmap array record the pixel values ​​of the i-th scan line of the image. When (biWidth biBitCount) MOD 32=0: n=(biwidth * biBitCount)/8
When (biWidth*biBitCount) MOD 32+0, n=(biWidth*biBitCount)/8+4
5.2.1.1.2 Relationship between pixel value and bitmap array (taking the first scan line as an example) Suppose the n bytes of the pixel value of the t-th scan line are bo, b1, b2, bn-1 respectively. Then: when biBitCount=1, the 7th bit of bo records the 1st pixel value of the 1st scan line of the bitmap, the 6th bit records the 2nd pixel value, and the 0th bit records the 8th pixel value: the 7th bit of bl records the 9th pixel value of the 1st scan line, the 6th bit records the 10th pixel value, *When biBitCount=4, the 7th to 4th bits of bo record the 1st pixel value of the ith scan line of the bitmap. The 7th to 4th bits of b1 record the 3rd pixel value of the 1st scan line of the bitmap, and the 3rd to 0th bits record the 4th pixel value.
SJ 20708--1998
When biBitCount=8, bo records the 1st pixel value of the i-th scan line of the bitmap, and bl records the 2nd pixel value of the 1st scan line.
When biBitCount=24, b0, b1, b2 record the 1st pixel value of the i-th scan line of the bitmap, and b3, b4, b5 record the 2nd pixel value of the 1st scan line. 5. 2. 1. 2 Compression Format
5.2. 1.2.18-bit compression format
When biCompress=1, the bitmap array data uses this compression format. The 8-bit compression format consists of two bytes. The first byte gives the number of consecutive pixels to be displayed, and the color scheme used is in the second byte. If the first byte is 0, the second byte has the following meanings! 0: End of line:
1: End of image:
n: (0x03
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