C#图片处理之: 锐化

使用数码相机，难免会拍糊一些照片。 但如果只是轻微糊掉，不妨可以尝试先锐化再缩小的办法补救。

锐化看起来很神奇，可以在一定程度内把不清晰的变清晰，这个和柔化正好相反。其实锐化的算法说穿了很简单：

取每一点的周围八点和自己本身共九个点。计算周围八个点的平均值，把自己减去这个平均值得到一个差值。这个差值乘上一个系数（也就是锐化的程度），加上自己的原始值，得到一个新值。这个新值就是我们要的锐化以后的值。

啥都不说了，上DEMO。值得注意的是，下面的算法纯粹是原理性的，其实可以作更进一步的优化。

        /**//// <summary>
        /// 锐化
        /// </summary>
        /// <param name="b">原始Bitmap</param>
        /// <param name="val">锐化程度。取值[0,1]。值越大锐化程度越高</param>
        /// <returns>锐化后的图像</returns>
        public static Bitmap KiSharpen(Bitmap b, float val)
        ...{
            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。位于边缘上的点不做改变。
                            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, r0;
                                int g1, g2, g3, g4, g5, g6, g7, g8, g0;
                                int b1, b2, b3, b4, b5, b6, b7, b8, b0;

                                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;
                                r0 = p[2];
                                g0 = p[1];
                                b0 = p[0];

                                vR = (float)r0 - (float)(r1 + r2 + r3 + r4 + r5 + r6 + r7 + r8) / 8;
                                vG = (float)g0 - (float)(g1 + g2 + g3 + g4 + g5 + g6 + g7 + g8) / 8;
                                vB = (float)b0 - (float)(b1 + b2 + b3 + b4 + b5 + b6 + b7 + b8) / 8;

                                vR = r0 + vR * val ;
                                vG = g0 + vG * val;
                                vB = b0 + vB * val;

                                if (vR > 0)
                                ...{
                                    vR = Math.Min(255, vR);
                                }
                                else
                                ...{
                                    vR = Math.Max(0, vR);
                                }

                                if (vG > 0)
                                ...{
                                    vG = Math.Min(255, vG);
                                }
                                else
                                ...{
                                    vG = Math.Max(0, vG);
                                }

                                if (vB > 0)
                                ...{
                                    vB = Math.Min(255, vB);
                                }
                                else
                                ...{
                                    vB = Math.Max(0, vB);
                                }

                                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 KiSharpen

那位说了，为什么不上优化后的代码呢？唉，要是我会的话不就贴出来了吗！