ID Number: Q79342
3.00 3.10
WINDOWS
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 reference words: 3.00 3.10 3.x