图像柔光效果（SoftGlow）的原理及其实现

由于CSDN博客和博客园的编辑方面有不一致的地方，导致文中部分图片错位，为不影响浏览效果，建议点击打开链接。

图像柔光效果在很多商业软件中都有实现，比如美图秀秀，光影魔术手等。其能针对原始图像产生一副新的比较平滑感觉光线比较柔和的效果，给人一种朦胧美，如下面几幅图所示：

目前，关于该算法的可控参数，美图秀秀只提供了一个程度（0-100%）控制量，其算法调节的效果和幅度都较小，光影魔术手有柔化程度和高光柔化两个参数，其中柔化程度控制柔化的朦胧效果，高光柔化调节图像的亮度。还有一些开源的软件如Imagestone、paint.net、gimp也有softglow算法，他们都提供了3个控制量：半径、亮度、对比度（锐度），其中Imagestone其实是翻译的gimp的算法，而GIMP和paint.net的算法在基本原理上是一样的，细节上有所区别而已。

我们以paint.net的实现过程为例进行说明，在paint.net的源代码中，GlowEffect.cs为实现该效果的文件，我抽取其部分源代码简要说明下这个算法的过程。

[csharp] view plaincopyprint?public GlowEffect() : base(StaticName, StaticImage, null, EffectDirectives.None, true)
{
    this.blurEffect = new BlurEffect();
    this.bcAdjustment = new BrightnessAndContrastAdjustment();
    this.screenBlendOp = new UserBlendOps.ScreenBlendOp();
}

        public GlowEffect() : base(StaticName, StaticImage, null, EffectDirectives.None, true)
        {
            this.blurEffect = new BlurEffect();
            this.bcAdjustment = new BrightnessAndContrastAdjustment();
            this.screenBlendOp = new UserBlendOps.ScreenBlendOp();
        }
     以及代码片段：

[csharp] view plaincopyprint?public override unsafe void Render(
         EffectConfigToken parameters,
         RenderArgs dstArgs,
         RenderArgs srcArgs,
         System.Drawing.Rectangle[] rois,
         int startIndex,
         int length)
     {
         // First we blur the source, and write the result to the destination surface
         // Then we apply Brightness/Contrast with the input as the dst, and the output as the dst
         // Third, we apply the Screen blend operation so that dst = dst OVER src

         ThreeAmountsConfigToken token = (ThreeAmountsConfigToken)parameters;

         AmountEffectConfigToken blurToken = new AmountEffectConfigToken(token.Amount1);
         this.blurEffect.Render(blurToken, dstArgs, srcArgs, rois, startIndex, length);

         BrightnessAndContrastAdjustmentConfigToken bcToken = new BrightnessAndContrastAdjustmentConfigToken(token.Amount2, token.Amount3);
         this.bcAdjustment.Render(bcToken, dstArgs, dstArgs, rois, startIndex, length);

         for (int i = startIndex; i < startIndex + length; ++i)
         {
             Rectangle roi = rois[i];

             for (int y = roi.Top; y < roi.Bottom; ++y)
             {
                 ColorBgra* dstPtr = dstArgs.Surface.GetPointAddressUnchecked(roi.Left, y);
                 ColorBgra* srcPtr = srcArgs.Surface.GetPointAddressUnchecked(roi.Left, y);

                 screenBlendOp.Apply(dstPtr, srcPtr, dstPtr, roi.Width);
             }
         }
     }

   public override unsafe void Render(
            EffectConfigToken parameters,
            RenderArgs dstArgs,
            RenderArgs srcArgs,
            System.Drawing.Rectangle[] rois,
            int startIndex,
            int length)
        {
            // First we blur the source, and write the result to the destination surface
            // Then we apply Brightness/Contrast with the input as the dst, and the output as the dst
            // Third, we apply the Screen blend operation so that dst = dst OVER src

ThreeAmountsConfigToken token = (ThreeAmountsConfigToken)parameters;

AmountEffectConfigToken blurToken = new AmountEffectConfigToken(token.Amount1);
this.blurEffect.Render(blurToken, dstArgs, srcArgs, rois, startIndex, length);

BrightnessAndContrastAdjustmentConfigToken bcToken = new BrightnessAndContrastAdjustmentConfigToken(token.Amount2, token.Amount3);
this.bcAdjustment.Render(bcToken, dstArgs, dstArgs, rois, startIndex, length);

            for (int i = startIndex; i < startIndex + length; ++i)
            {

补充：软件开发 , C# ,