如何绘制减光边框（外部发光效果）？

Question

怎样绘制一个轻量化的边框像这样与GDI/GDI +：

任何人都可以给我一个思路感谢。

Answer 1

• 绘制边界进入图像比边界本身稍大。
• 模糊它。
• 清除边框内部。
• 在模糊图像上绘制边框。
• 将该图像绘制到目的地。

Answer 2

使用GDI +，我会建议你使用PathGradientBrush。它允许您在边缘周围填充一系列颜色的区域，这些颜色都会向中心颜色混合。在这种情况下，您可能只需要1种边缘颜色。为圆角矩形创建的GraphicsPath和使用FillPath（）用PathGradientBrush来填补它：

GraphicsPath graphicsPath; 

//rect - for a bounding rect 
//radius - for how 'rounded' the glow will look 
int diameter = radius * 2; 

graphicsPath.AddArc(Rect(rect.X, rect.Y, diameter, diameter) 180.0f, 90.0f); 
graphicsPath.AddArc(Rect(rect.X + rect.Width - diameter, rect.Y, diameter, diameter), 270.0f, 90.0f); 
graphicsPath.AddArc(Rect(rect.X + rect.Width - diameter, rect.Y + rect.Height - diameter, diameter, diameter), 0.0f, 90.0f); 
graphicsPath.AddArc(Rect(rect.X, rect.Y + rect.Height - diameter, diameter, diameter), 90.0f, 90.0f); 
graphicsPath.CloseFigure(); 

PathGradientBrush brush(&graphicsPath); 
brush.SetCenterColor(centerColor); //would be some shade of blue, following your example 
int colCount = 1; 
brush.SetSurroundColors(surroundColor, &colCount); //same as your center color, but with the alpha channel set to 0 

//play with these numbers to get the glow effect you want 
REAL blendFactors[] = {0.0, 0.1, 0.3, 1.0}; 
REAL blendPos[] = {0.0, 0.4, 0.6, 1.0}; 
//sets how transition toward the center is shaped 
brush.SetBlend(blendFactors, blendPos, 4); 
//sets the scaling on the center. you may want to have it elongated in the x-direction 
brush.SetFocusScales(0.2f, 0.2f); 

graphics.FillPath(&brush, &graphicsPath);