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L_GetResizedRowCol

#include "l_bitmap.h"

L_LTKRN_API L_INT L_GetResizedRowCol(pResizeData, pBuffer, nRow, nCol, uBytes)

Retrieves resized data, one line at a time.

Parameters

L_VOID* pResizeData

Pointer to the resizing process. This is obtained from L_StartResizeBitmap.

L_UCHAR *pBuffer

Pointer to the buffer to hold the image data that this function gets. You must allocate the buffer before calling this function, and the buffer must be large enough to hold the image data.

L_INT nRow

The number of the row to retrieve. The first row is 0, and the last row is 1 less than the bitmap height.

L_INT nCol

The column offset within the row to retrieve. The first column offset is 0, and the last column offset is 1 less than the bitmap width.

L_SIZE_T uBytes

The number of bytes to retrieve. Consider the bits per pixel, and avoid specifying a number that goes past the end of the row.

Value	Meaning
1-bit bitmap	Each byte represents 8 pixels.
4-bit bitmap	Each byte represents 2 pixels.
8-bit bitmap	Each byte represents 1 pixel.
16-bit bitmap	Every 2 bytes represents one pixel.
24-bit bitmap	Every three bytes represents one pixel.
32-bit bitmap	Every four bytes represents one pixel.
48-bit bitmap	Every six bytes represents one pixel.
64-bit bitmap	Every eight bytes represents one pixel.

You can use the bitmap handle's BitsPerPixel field with integer math to calculate the number of bytes needed for a particular number of pixels. For example:

NumberOfBytes = (Bitmap.BitsPerPixel * NumberOfPixels) / 8; 
if ((Bitmap.BitsPerPixel * NumberOfPixels) % 8) 
   ++NumberOfBytes; /* Round up if necessary for a 1- or 4-bit image */

Returns

Value	Meaning
>=1	The number of bytes copied.
< 1	An error occurred. Refer to Return Codes.

Comments

By using this low-level function to get any part of a row, you can write a procedure that accesses a single pixel or a rectangular area within the bitmap.

This function accepts an offset parameter nCol in pixels and a length uBytes in bytes. Therefore, you must consider the bits per pixel of the bitmap when specifying these parameters. The following table describes the rules:

Bits Per Pixel	Column Offset (in Pixels)	Bytes to Get
1	Must be a multiple of 8 (such as 0, 8, or 16).	Can be any number up to the end of the row. Consider that there are 8 pixels per byte.
4	Must be an even number (such as 0, 2, or 4).	Can be any number up to the end of the row. Consider that there are 2 pixels per byte.
8	Can be any column within the bitmap.	Can be any number up to the end of the row. Consider that there is 1 pixel per byte.
16	Can be any column within the bitmap.	Must be a multiple of 2 (such as 2, 4, or 6), because there are 2 bytes per pixel.
24	Can be any column within the bitmap.	Must be a multiple of 3 (such as 3, 6, or 9), because there are 3 bytes per pixel.
32	Can be any column within the bitmap.	Must be a multiple of 4 (such as 4, 8, or 12), because there are 4 bytes per pixel.
48	Can be any column within the bitmap.	Must be a multiple of 6 (such as 6, 12, or 18), because there are 6 bytes per pixel.
64	Can be any column within the bitmap.	Must be a multiple of 8 (such as 8, 16, or 24), because there are 8 bytes per pixel.