C#图片处理之:最简单的柔化算法

原文http://blog.csdn.net/ki1381/archive/2007/05/10/1603602.aspx
与锐化相反，柔化是使图片看起来更柔滑（其实也是模糊的委婉的说法）。柔化的一个最简单的实现算法就是取图片上的每一点（图片边缘点忽略），计算它周围八个点的平均值作为新像素值。想想也是，之所以看起来模糊，确实是因为周围的点长的有点像，区别不太明显。

        // ============================柔化==============================
        /**//// <summary>
        /// 柔化
        /// <param name="b">原始图</param>
        /// <returns>输出图</returns>
        public static Bitmap KiBlur(Bitmap b)
        ...{

            if (b == null)
            ...{
                return null;
            }

            int w = b.Width;
            int h = b.Height;

            try
            ...{

                Bitmap bmpRtn = new Bitmap(w, h, PixelFormat.Format24bppRgb);

                BitmapData srcData = b.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
                BitmapData dstData = bmpRtn.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb);

                unsafe
                ...{
                    byte* pIn = (byte*)srcData.Scan0.ToPointer();
                    byte* pOut = (byte*)dstData.Scan0.ToPointer();
                    int stride = srcData.Stride;
                    byte* p;

                    for (int y = 0; y < h; y++)
                    ...{
                        for (int x = 0; x < w; x++)
                        ...{
                            //取周围9点的值
                            if (x == 0 || x == w - 1 || y == 0 || y == h - 1)
                            ...{
                                //不做
                                pOut[0] = pIn[0];
                                pOut[1] = pIn[1];
                                pOut[2] = pIn[2];
                            }
                            else
                            ...{
                                int r1, r2, r3, r4, r5, r6, r7, r8, r9;
                                int g1, g2, g3, g4, g5, g6, g7, g8, g9;
                                int b1, b2, b3, b4, b5, b6, b7, b8, b9;

                                float vR, vG, vB;

                                //左上
                                p = pIn - stride - 3;
                                r1 = p[2];
                                g1 = p[1];
                                b1 = p[0];

                                //正上
                                p = pIn - stride;
                                r2 = p[2];
                                g2 = p[1];
                                b2 = p[0];

                                //右上
                                p = pIn - stride + 3;
                                r3 = p[2];
                                g3 = p[1];
                                b3 = p[0];

                                //左侧
                                p = pIn - 3;
                                r4 = p[2];
                                g4 = p[1];
                                b4 = p[0];

                                //右侧
                                p = pIn + 3;
                                r5 = p[2];
                                g5 = p[1];
                                b5 = p[0];

                                //右下
                                p = pIn + stride - 3;
                                r6 = p[2];
                                g6 = p[1];
                                b6 = p[0];

                                //正下
                                p = pIn + stride;
                                r7 = p[2];
                                g7 = p[1];
                                b7 = p[0];

                                //右下
                                p = pIn + stride + 3;
                                r8 = p[2];
                                g8 = p[1];
                                b8 = p[0];

                                //自己
                                p = pIn;
                                r9 = p[2];
                                g9 = p[1];
                                b9 = p[0];

                                vR = (float)(r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8 + r9);
                                vG = (float)(g1 + g2 + g3 + g4 + g5 + g6 + g7 + g8 + g9);
                                vB = (float)(b1 + b2 + b3 + b4 + b5 + b6 + b7 + b8 + b9);

                                vR /= 9;
                                vG /= 9;
                                vB /= 9;

                                pOut[0] = (byte)vB;
                                pOut[1] = (byte)vG;
                                pOut[2] = (byte)vR;

                            }

                            pIn += 3;
                            pOut += 3;
                        }// end of x

                        pIn += srcData.Stride - w * 3;
                        pOut += srcData.Stride - w * 3;
                    } // end of y
                }

                b.UnlockBits(srcData);
                bmpRtn.UnlockBits(dstData);

                return bmpRtn;
            }
            catch
            ...{
                return null;
            }

        } // end of KiBlur

当然这是最简单的一种，不支持柔化半径选择。实际中通常需要自定义模糊的程度，这个下回再谈。