STARTDECOMPRESSDATA

typedef struct _STARTDECOMPRESSDATA 
{ 
   L_UINT uStructSize; 
   pBITMAPHANDLE pBitmap; 
   L_UINT uBitmapStructSize; 
   L_UINT uStripsOrTiles; 
   L_UINT uFormat; 
   L_INT nWidth; 
   L_INT nHeight; 
   L_INT nBitsPerPixel; 
   L_INT nViewPerspective; 
   L_INT nRawOrder; 
   L_INT nLoadOrder; 
   L_INT nXResolution; 
   L_INT nYResolution; 
   FILEREADCALLBACK pfnReadCallback; 
   L_RGBQUAD Palette[256]; 
   L_UINT uFlags; 
   L_VOID* pUserData; 
   L_UINT rgbColorMask[3]; 
   L_INT nPhotoInt; 
   L_INT nPlanarConfig; 
   L_UINT uReserved1; 
} STARTDECOMPRESSDATA, *pSTARTDECOMPRESSDATA; 

The STARTDECOMPRESSDATA structure provides decompression to the L_StartDecompressBuffer function.

Members

uStructSize

Size of this structure in bytes, for versioning. Use the sizeof() operator to calculate this value.

pBitmap

Pointer to the bitmap handle in which to load the image.

uBitmapStructSize

Size of the structure pointed to by pBitmap, for versioning. Use sizeof(BITMAPHANDLE).

uStripsOrTiles

Flag that indicates whether strips or tiles are being decompressed. Strips have a width equal to the bitmap width, but tiles can have a width that is less than the bitmap width. Possible values are:

Value Meaning
DECOMPRESS_STRIPS Decompress strips of data.
DECOMPRESS_TILES Decompress tiles of data. The pfnReadCallback is not called if this option is set.

uFormat

Format of the image to decompress. Possible values are:

Value Meaning
FILE_JPEG JPEG file
FILE_RAW_RLE4 RAW file with RLE compression, 4 bits per pixel
FILE_RAW_RLE8 RAW file with RLE compression, 8 bits per pixel
FILE_RAW_BITFIELDS RAW file with bitfield compression
FILE_RAW_PACKBITS RAW file with packed bits compression
FILE_RAW_CCITT RAW file with CCITT compression.
FILE_FAX_G3_1D Fax file with G3 one-dimensional compression
FILE_FAX_G3_2D Fax file with G3 two-dimensional compression
FILE_FAX_G4 Fax file with G4 compression
FILE_LEAD LEAD file

nWidth

Bitmap width.

nHeight

Bitmap height.

nBitsPerPixel

Bits per pixel of the compressed data.

nViewPerspective

View perspective of the compressed data. Possible values are:

Value Meaning
TOP_LEFT Top-left of image is first in memory.
TOP_LEFT90 TOP_LEFT rotated clockwise by 90 degrees.
TOP_LEFT180 TOP_LEFT rotated clockwise by 180 degrees.
TOP_LEFT270 TOP_LEFT rotated clockwise by 270 degrees.
BOTTOM_LEFT Bottom-left of image is first in memory.
BOTTOM_LEFT90 BOTTOM_LEFT rotated clockwise by 90 degrees.
BOTTOM_LEFT180 BOTTOM_LEFT rotated clockwise by 180 degrees.
BOTTOM_LEFT270 BOTTOM_LEFT rotated clockwise by 270 degrees

nRawOrder

Color order of 24-bit raw data. This is ignored if the image is palettized. Possible values are:

Value Meaning
ORDER_RGB RGB
ORDER_BGR BGR

nLoadOrder

Desired color order after a 24-bit image is loaded. This is ignored if the image is palettized. Possible values are:

Value Meaning
ORDER_RGB RGB
ORDER_BGR BGR

nXResolution

Horizontal resolution, in dots per inch.

nYResolution

Vertical resolution, in dots per inch.

pfnReadCallback

Optional callback function for additional processing.

If you do not provide a callback function, use NULL as the value of this parameter.

If you do provide a callback function, use the function pointer as the value of this parameter.

The callback function must adhere to the function prototype described in FILEREADCALLBACK Function.

Palette

Palette for uncompressed data that is 8 bits per pixel or less. Fill in the first 2BitsPerPixel entries in this palette and include DECOMPRESS_PALETTE in the uFlags field.

uFlags

Flags that affect the decompression process. Possible values are:

Value Meaning
DECOMPRESS_LSB Fill the least significant bit first.
DECOMPRESS_PAD4 Pad each line to a multiple of 4 bytes.
DECOMPRESS_PALETTE A palette is supplied in the rgbQuad field.

pUserData

Void pointer that you can use to pass one or more additional parameters that the callback function needs.

To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure.

If the additional parameters are not needed, you can pass NULL in this parameter.

rgbColorMask

An array of L_UINT32 values that represent RGB color masks. rgbColorMask[0] is the red mask; rgbColorMask[1] is the green mask; rgbColorMask[2] is the blue mask. This field is valid only if uFormat is FILE_RAW_BITFIELDS.

nPhotoInt

Value that represents color information. Possible values are:

For FILE_RAW_CCITT, FILE_RAW_G3_1D, FILE_RAW_G3_2D and FILE_FAX_G4

Value Meaning
0 White is zero
1 Black is zero

For FILE_RAW_PACKBITS

Value Meaning
2 There is no color map (RGB)
5 Separated CMYK
6 YC b C r color space
8 1976 CIE Lab

nPlanarConfig

Planar configuration. This value is used only if uFormat is FILE_RAW_PACKBITS. Otherwise, it is ignored. Possible values are:

Value Meaning
1 Chunky
2 Planar format

uReserved1

Reserved for future use. Pass 0.

Comments

As an example, with 16-bit data arranged as RRR RRGG GGGB BBBB, the masks would be:

rgbColorMask[0] = 0x7C00
rgbColorMask[1] = 0x0E30
rgbColorMask[2] = 0x001F

For 32-bit data, the only valid data is RRRR RRRR GGGG GGGG BBBB BBBB. The masks would be:

rgbColorMask[0] = 0xFF0000
rgbColorMask[1] = 0x00FF00
rgbColorMask[2] = 0x0000FF

Some functions which take this structure as a parameter require that the structure be initialized prior to the function call. You must set the uStructSize member to the total size, in bytes, of the structure. Use the sizeof() operator to calculate this value. Functions that do not require the structure be initialized will take the total size of the structure, in bytes, as an additional function parameter.

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