c – OpenGL位图程序只显示白色,黑色和黄色？

void Load_Image(HDC hDC,string File_Name,int x_position,int y_position,int length,int height)
{     
bitmap_image image(File_Name);      // Open the bitmap
unsigned char red;
unsigned char green;
unsigned char blue;
restart:
image.get_pixel(x_position,y_position,red,green,blue);     // Get the red green and blue from x_position and y_position and store it in red green and blue. 
glBegin (GL_TRIANGLES);                                        // Make a pixel at x_position and y_position with red green and blue.
glColor3f (red,blue);
glVertex2f (-1 + 0.0015 * x_position,1 - 0.003 * y_position);
glVertex2f (-1 + 0.0015 * x_position,0.997 - 0.003 * y_position);
glVertex2f (-0.9985 + 0.0015 * x_position,1 - 0.003 * y_position);
glEnd();
glBegin (GL_TRIANGLES);
glColor3f (red,1 - 0.003 * y_position);
glVertex2f (-0.9985 + 0.0015 * x_position,0.997 - 0.003 * y_position);
glEnd();
if (x_position==length)      // If x_position equals to length of bmp set x_position to 0 and add 1 to y_position.
{
if (y_position==height)      // If bmp is done loading go to done.
{
goto done;
}
x_position = 0;
y_position = y_position + 1;
}
x_position = x_position + 1;
goto restart;
done:         
SwapBuffers(hDC);            // Put it on the screen.
}

关于什么是错的任何想法？
谢谢！