Microsoft KB Archive/79342

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Windows Paintbrush File Format

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Q79342

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The information in this article applies to:


 * Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1

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SUMMARY
This article provides the format of Windows Paintbrush files.

MORE INFORMATION
Paintbrush files are preceded by 32 bytes of header information. Following the header is an index table into run-length encoded data.

Header
The header structure is defined in the C programming language, as follows:

typedef struct { WORD  key1; WORD key2; WORD dxFile; WORD dyFile;

/* NOTE: PBRUSH.EXE version 3.0 and 3.1 ignore the remaining values */ /* in this structure. Future versions may or may not. */

WORD ScrAspectX; WORD ScrAspectY; WORD PrnAspectX; WORD PrnAspectY; WORD dxPrinter; WORD dyPrinter; WORD AspCorX; WORD AspCorY; WORD wCheck; WORD res1; WORD res2; WORD res3; WORD res4; } FILEHDR; The first 32 bytes contain the header information described by the above structure:

Bytes  Name     Win 1.0   Win 2.0           Win 3.0 -       ---   ---           ---

0 - 1  Key1     0x6144    0x694C      |0x6144| or |0x694C| 2 - 3  Key2     0x4D6E    0x536E      |0x4D6E|    |0x536E|

4 - 5  dxFile      X-dimension size of bitmap, in pixels

6 - 7  dyFile      Y-dimension size of bitmap, in pixels

8 - 9  SrcAspectX  Aspect ratio of the screen for which file was created. Obtained from GetDeviceCaps(hScreenDC,                   ASPECTX);

10 - 11 SrcAspectY Aspect ratio of the screen for which file was created. Obtained from GetDeviceCaps(hScreenDC,                   ASPECTY);

12 - 13 PrnAspectX Aspect ratio of the printer for which file was created. Obtained from GetDeviceCaps(hPrinterDC,                   ASPECTX);

14 - 15 PrnAspectY Aspect ratio of the printer for which file was created. Obtained from GetDeviceCaps(hPrinterDC,                   ASPECTY);

16 - 17 dxPrinter  Resolution of the printer for which file was created. Contains the number of pixels in the x                   direction on the printer. The selected paper and printer orientation affect this value.

18 - 19 dyPrinter  Resolution of the printer for which file was created. Contains the number of pixels in the y                   direction on the printer. The selected paper and printer orientation affect this value.

20 - 21 AspCorX    Not used. Set to zero.

22 - 23 AspCorY    Not used. Set to zero.

24 - 25 wCheck     Checksum field. Makes sure that this file is Paint format.

26 - 31 Reserved

Index
The Paintbrush bitmap is run-length encoded. Each scan line is encoded separately. The length of the resulting encoded string depends on the pattern of the bitmap. There is an index table following the header. Each entry of this index corresponds to a scan line. It is an unsigned integer and shows the length of the encoded data. Following this table is the encoded data.

  32 - xxx     xxx = 32 + sizeof(unsigned int) * dyPrinter

ALGORITHM FOR ENCODING
Paint encoding is read in BYTES. There are two types of encoded data: one starts with 0 (zero), the other starts with a nonzero value.

If the data starts with 0, it is a repeated byte pattern. The byte following the 0 tells how many times to repeat the pattern and the subsequent byte is the pattern itself. For example, 0, 0x80, 0xff, should be expanded to eighty (hex) bytes of 0xff.

If the data starts with a nonzero value, X, the following X number of bytes contain unmodified bitmap data, without recognizable pattern. Each scan line can be composed of several of the above mentioned groups of data. Of course, the groups should alternate, meaning that a scan line can start with a repeated pattern followed by some random pattern, which is followed by another repeated pattern.

To reach the data for the nth scan line, add up the values in the index table from entry 0 to entry n - 1.

Additional query words: 3.00 no32bit 3.10

Keywords : kb16bitonly

Issue type :

Technology : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310