在VB6下实现窗体的淡入淡出,还有渐变效果。把以前的微软出的代码做了部分改进，还加了渐变效果。也可无阴影。-In the form of under VB6 fade, as well as the effect of gradual change. Microsoft out of the previous code to do some improvements, also increases the effect of the gradient. Can be no shadow.