thirty nine

CxImage cx;
cx.Load(image_path, CXIMAGE_FORMAT_JPG);
unsigned char* pImageBytes = (unsigned char*)cx.GetBits();

int width = cx.GetWidth();
int height = cx.GetHeight();

long size_origin = cx.GetSize();
long size_dest = size_origin + width*height;

long stride_origin = size_origin/height;
long stride_dest = size_dest/height;

int bpp_origin = stride_origin/ width;
int bpp_dest   = 4;

unsigned char* pCairoBytes = (unsigned char*)malloc(size_dest);
const unsigned char alpha = 0xff;

int i, j;
long row_start_pos_origin, row_start_pos_dest;

for(i = 0; i < height; i++ )
{
	row_start_pos_origin = (height - i - 1) * stride_origin;
	row_start_pos_dest = i * stride_dest;
	for(j = 0; j < width; j++)
	{
		memcpy( (pCairoBytes + row_start_pos_dest   + j*bpp_dest), 
			(pImageBytes + row_start_pos_origin + j*bpp_origin), 3);         // rgb
		memcpy( (pCairoBytes + row_start_pos_dest + j*bpp_dest + 3), &alpha, 1); // alpha
	}
}

cairo_surface_t* 
image_surface = cairo_image_surface_create_for_data(pCairoBytes, CAIRO_FROMAT_ARGB32, 
                                                    width, height, stride_dest);