L_GetPixelData

#include "l_bitmap.h"

L_LTKRN_API L_INT L_GetPixelData(pBitmap, pData, nRow, nCol, uBytes)

pBITMAPHANDLE pBitmap;

pointer to the bitmap handle

L_VOID* pData;

pointer to a buffer

L_INT nRow;

row number of the pixel

L_INT nCol;

column number of the pixel

L_SIZE_T uBytes;

size of the buffer

Gets the data of the specified pixel. No transformations are performed on the pixel data.

Parameter

Description

pBitmap

Pointer to the bitmap handle referencing the bitmap.

pData

Pointer to a buffer to be updated with the pixel data. This buffer should be able to store uBytes bytes.

nRow

The row number of the pixel. This is a zero-based value.

nCol

The column number of the pixel. This is a zero-based value.

uBytes

Size of the buffer pointed to by pData. The size should be large enough to contain the data for the pixel. The minimum size can be calculated with the following formula: (pBitmap->BitsPerPixel + 7) / 8.

Returns

SUCCESS

The function was successful.

< 1

An error occurred. Refer to Return Codes.

Comments

The bitmap's memory must be locked when you use this function. Normally, call L_AccessBitmap to lock the memory before starting an operation that uses this function and then call L_ReleaseBitmap when the operation is finished.

This function should be called only for 8, 16, 24, 32, 48 and 64-bit bitmaps. Here is how it works:

This function will return an error if uBytes is smaller than it should be. The minimum value for uBytes is indicated in a formula above.

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_AccessBitmap, L_ReleaseBitmap, L_GetBitmapRow, L_PutBitmapRow, L_GetBitmapRowCol, L_PutBitmapRowCol, L_GetPixelColor, L_PutPixelColor, L_PutPixelData

Topics:

Raster Image Functions: Getting and Setting Pixel Values

 

Processing an Image

Example

This example uses L_GetPixelData and L_PutPixelData to swap the R and G values for a particular pixel. This example will work only with 24, 32, 48 and 64-bit bitmaps.

L_INT GetPixelDataExample(pBITMAPHANDLE  pBitmap, 
                                          L_INT          nRow, 
                                          L_INT          nCol) 
{ 
   L_INT nRet; 
   L_UINT uVal; 
 
   if(pBitmap->BitsPerPixel == 24 || pBitmap->BitsPerPixel == 32) 
   { 
      L_UCHAR aPixel[4]; // make it large enough for both bitmap types 
      L_AccessBitmap(pBitmap); 
      nRet = L_GetPixelData(pBitmap, aPixel, nRow, nCol, sizeof(aPixel)); 
      L_ReleaseBitmap(pBitmap); 
      if(nRet != SUCCESS) 
         return nRet; 
      // swap the R and B values 
      uVal = aPixel[0]; aPixel[0] = aPixel[2]; aPixel[2] = (L_UCHAR)uVal; 
      L_AccessBitmap(pBitmap); 
      // put back the transformed pixel       
      nRet = L_PutPixelData(pBitmap, aPixel, nRow, nCol, sizeof(aPixel)); 
      L_ReleaseBitmap(pBitmap); 
      if(nRet != SUCCESS) 
         return nRet; 
   } 
   else if(pBitmap->BitsPerPixel == 48 || pBitmap->BitsPerPixel == 64) 
   { 
      L_UINT16 aPixel[4]; // make it large enough for both bitmap types 
      L_AccessBitmap(pBitmap); 
      nRet = L_GetPixelData(pBitmap, aPixel, nRow, nCol, sizeof(aPixel)); 
      L_ReleaseBitmap(pBitmap); 
      if(nRet != SUCCESS) 
         return nRet; 
      // swap the R and B values 
      uVal = aPixel[0]; aPixel[0] = aPixel[2]; aPixel[2] = (L_UINT16)uVal; 
      L_AccessBitmap(pBitmap); 
      // put back the transformed pixel 
      nRet = L_PutPixelData(pBitmap, aPixel, nRow, nCol, sizeof(aPixel)); 
      L_ReleaseBitmap(pBitmap); 
      if(nRet != SUCCESS) 
         return nRet; 
   } 
   return SUCCESS; 
} 

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