about texture

I am so sorry i have too many question to ask, but please help me
here is another question.
loadbitmapwithalpha()function frome the book.
unsigned char *CTexture::LoadBitmapFileWithAlpha(char *filename, BITMAPINFOHEADER *bitmapInfoHeader)
{
unsigned char *bitmapImage = LoadBitmapFile(filename, bitmapInfoHeader);
unsigned char *bitmapWithAlpha = (unsigned char *)malloc(bitmapInfoHeader->biSizeImage * 4 / 3);

// loop through the bitmap data
for (int src = 0, dst = 0; src < bitmapInfoHeader->biSizeImage; src +=3, dst +=4)
{
// if the pixel is black, set the alpha to 0. Otherwise, set it to 255.
if (bitmapImage[src] == 0 && bitmapImage[src+1] == 0 && bitmapImage[src+2] == 0)
bitmapWithAlpha[dst+3] = 0;
else
bitmapWithAlpha[dst+3] = 0xFF;

// copy pixel data over
bitmapWithAlpha[dst] = bitmapImage[src];
bitmapWithAlpha[dst+1] = bitmapImage[src+1];
bitmapWithAlpha[dst+2] = bitmapImage[src+2];
}

free(bitmapImage);

return bitmapWithAlpha;
} // end LoadBitmapFileWithAlpha()

// LoadPCXFile()
// desc: loads a PCX file into memory
unsigned char *CTexture::LoadPCXFile(char *filename, PCXHEADER *pcxHeader)
{
int idx = 0; // counter index
int c; // used to retrieve a char from the file
int i; // counter index
int numRepeat;
FILE *filePtr; // file handle
int width; // pcx width
int height; // pcx height
unsigned char *pixelData; // pcx image data
unsigned char *paletteData; // pcx palette data

// open PCX file
filePtr = fopen(filename, "rb");
if (filePtr == NULL)
return NULL;

// retrieve first character; should be equal to 10
c = getc(filePtr);
if (c != 10)
{
fclose(filePtr);
return NULL;
}

// retrieve next character; should be equal to 5
c = getc(filePtr);
if (c != 5)
{
fclose(filePtr);
return NULL;
}

// reposition file pointer to beginning of file
rewind(filePtr);

// read 4 characters of data to skip
fgetc(filePtr);
fgetc(filePtr);
fgetc(filePtr);
fgetc(filePtr);

// retrieve leftmost x value of PCX
pcxHeader->xMin = fgetc(filePtr); // loword
pcxHeader->xMin |= fgetc(filePtr) << 8; // hiword

// retrieve bottom-most y value of PCX
pcxHeader->yMin = fgetc(filePtr); // loword
pcxHeader->yMin |= fgetc(filePtr) << 8; // hiword

// retrieve rightmost x value of PCX
pcxHeader->xMax = fgetc(filePtr); // loword
pcxHeader->xMax |= fgetc(filePtr) << 8; // hiword

// retrieve topmost y value of PCX
pcxHeader->yMax = fgetc(filePtr); // loword
pcxHeader->yMax |= fgetc(filePtr) << 8; // hiword

// calculate the width and height of the PCX
width = pcxHeader->xMax - pcxHeader->xMin + 1;
height = pcxHeader->yMax - pcxHeader->yMin + 1;

// allocate memory for PCX image data
pixelData = (unsigned char*)malloc(width*height);

// set file pointer to 128th byte of file, where the PCX image data starts
fseek(filePtr, 128, SEEK_SET);

// decode the pixel data and store
while (idx < (width*height))
{
c = getc(filePtr);
if (c > 0xbf)
{
numRepeat = 0x3f & c;
c = getc(filePtr);

for (i = 0; i < numRepeat; i++)
{
pixelData[idx++] = c;
}
}
else
pixelData[idx++] = c;

fflush(stdout);
}

// allocate memory for the PCX image palette
paletteData = (unsigned char*)malloc(768);

// palette is the last 769 bytes of the PCX file
fseek(filePtr, -769, SEEK_END);

// verify palette; first character should be 12
c = getc(filePtr);
if (c != 12)
{
fclose(filePtr);
return NULL;
}

// read and store all of palette
for (i = 0; i < 768; i++)
{
c = getc(filePtr);
paletteData = c;
}

// close file and store palette in header
fclose(filePtr);
pcxHeader->palette = paletteData;

// return the pixel image data
return pixelData;
}
the same thing happen again, it is totally ok that i use this function to load the bitmap in that book, but is cant work when i use my owned bitmap, these bit maps created by photoshop can be successfully loaded by the loading function ni nehe site, by you know ,that function could not define colorkey.thank you very much !!!!!

i am sorry something wrong with my keyboard, i wrongly copy all the function below, you just need to check the loadbitmapwithalpha()function ,thank you