L_GetResizedRowCol

#include "l_bitmap.h"

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

L_VOID* pResizeData;

pointer to the bitmap handle

L_UCHAR *pBuffer;

pointer to the target buffer

L_INT nRow;

number of the row to retrieve

L_INT nCol;

column offset within the row to retrieve

L_SIZE_T uBytes;

number of bytes to retrieve

Retrieves resized data, one line at a time.

Parameter Description
pResizeData Pointer to the resizing process. This is obtained from L_StartResizeBitmap.
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.
nRow The number of the row to retrieve. The first row is 0, and the last row is 1 less than the bitmap height.
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.
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

>=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.

Do not pass a value in uBytes that goes past the end of the row.

The process is faster when rows are retrieved sequentially, either top-down or bottom-up.

Required DLLs and Libraries

LTKRN

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Win32, x64, Linux.

See Also

Functions:

L_StartResize, L_StopResize, RESIZECALLBACK

Example

For an example, refer to L_StartResizeBitmap.

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