CMYK separated images

BOOL fipImage::splitCMYK(fipImage& newc, fipImage& newm, fipImage& newy, fipImage& newk){
  if (_dib){

    if(!FreeImage_HasPixels(_dib)) return FALSE;

    // src image should be CMYK
    FREE_IMAGE_COLOR_TYPE color_type = FreeImage_GetColorType(_dib);
    if (color_type !=FIC_CMYK){
      return FALSE;
    }
    
    FREE_IMAGE_TYPE image_type = FreeImage_GetImageType(_dib);
    unsigned bpp = FreeImage_GetBPP(_dib);

    // allocate a 8-bit dib
    unsigned width  = FreeImage_GetWidth(_dib);
    unsigned height = FreeImage_GetHeight(_dib);

    FIBITMAP *dst[4] = {NULL, NULL, NULL, NULL};

    for (int i = 0; i < 4; ++i){
      dst[i] = FreeImage_Allocate(width, height, 8);
      if(!dst) continue;

      // build a greyscale palette
      RGBQUAD *pal = FreeImage_GetPalette(dst[i]);
      for(int i = 0; i < 256; i++) {
        pal[i].rgbBlue = pal[i].rgbGreen = pal[i].rgbRed = (BYTE)i;
      }
    }
    
    // perform extraction

    int bytespp = bpp / 8;  // bytes / pixel

    for(unsigned y = 0; y < height; y++) {
      BYTE *src_bits = FreeImage_GetScanLine(_dib, y);
      BYTE *c_bits = FreeImage_GetScanLine(dst[0], y);
      BYTE *m_bits = FreeImage_GetScanLine(dst[1], y);
      BYTE *y_bits = FreeImage_GetScanLine(dst[2], y);
      BYTE *k_bits = FreeImage_GetScanLine(dst[3], y);

      for(unsigned x = 0; x < width; x++) {
        c_bits[x] = src_bits[0];
        m_bits[x] = src_bits[1];
        y_bits[x] = src_bits[2];
        k_bits[x] = src_bits[3];
        src_bits += bytespp;
      
      }
    }

    //
    newc = dst[0];
    newm = dst[1];
    newy = dst[2];
    newk = dst[3];

    return (newc.isValid() && newm.isValid() && newy.isValid() && newk.isValid());
  }
  return FALSE;
}