图片处理

 public class Image
    {
        #region 正方型裁剪并缩放

        /// <summary>
        /// 正方型裁剪
        /// 以图片中心为轴心，截取正方型，然后等比缩放
        /// 用于头像处理
        /// </summary>
        /// <param name="fromFile">原图Stream对象</param>
        /// <param name="fileSaveUrl">缩略图存放地址</param>
        /// <param name="side">指定的边长（正方型）</param>
        /// <param name="quality">质量（范围0-100）</param>
        public static void CutForSquare(Stream fromFile, string fileSaveUrl, int side, int quality)
        {
            //创建目录
            var dir = Path.GetDirectoryName(fileSaveUrl);
            if (dir != null && !Directory.Exists(dir)) Directory.CreateDirectory(dir);

            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
            var initImage = System.Drawing.Image.FromStream(fromFile, true);

            //原图宽高均小于模版，不作处理，直接保存
            if (initImage.Width <= side && initImage.Height <= side) initImage.Save(fileSaveUrl, ImageFormat.Jpeg);
            else
            {
                //原始图片的宽、高
                var initWidth = initImage.Width;
                var initHeight = initImage.Height;

                //非正方型先裁剪为正方型
                if (initWidth != initHeight)
                {
                    //截图对象
                    System.Drawing.Image pickedImage;
                    Graphics pickedG;

                    //宽大于高的横图
                    if (initWidth > initHeight)
                    {
                        //对象实例化
                        pickedImage = new Bitmap(initHeight, initHeight);
                        pickedG = Graphics.FromImage(pickedImage);
                        //设置质量
                        pickedG.InterpolationMode = InterpolationMode.HighQualityBicubic;
                        pickedG.SmoothingMode = SmoothingMode.HighQuality;
                        //定位
                        var fromR = new Rectangle((initWidth - initHeight)/2, 0, initHeight, initHeight);
                        var toR = new Rectangle(0, 0, initHeight, initHeight);
                        //画图
                        pickedG.DrawImage(initImage, toR, fromR, GraphicsUnit.Pixel);
                        //重置宽
                        initWidth = initHeight;
                    }
                        //高大于宽的竖图
                    else
                    {
                        //对象实例化
                        pickedImage = new Bitmap(initWidth, initWidth);
                        pickedG = Graphics.FromImage(pickedImage);
                        //设置质量
                        pickedG.InterpolationMode = InterpolationMode.HighQualityBicubic;
                        pickedG.SmoothingMode = SmoothingMode.HighQuality;
                        //定位
                        var fromR = new Rectangle(0, (initHeight - initWidth)/2, initWidth, initWidth);
                        var toR = new Rectangle(0, 0, initWidth, initWidth);
                        //画图
                        pickedG.DrawImage(initImage, toR, fromR, GraphicsUnit.Pixel);
                        //重置高
                        initHeight = initWidth;
                    }

                    //将截图对象赋给原图
                    initImage = (System.Drawing.Image)pickedImage.Clone();
                    //释放截图资源
                    pickedG.Dispose();
                    pickedImage.Dispose();
                }

                //缩略图对象
                System.Drawing.Image resultImage = new Bitmap(side, side);
                var resultG = Graphics.FromImage(resultImage);
                //设置质量
                resultG.InterpolationMode = InterpolationMode.HighQualityBicubic;
                resultG.SmoothingMode = SmoothingMode.HighQuality;
                //用指定背景色清空画布
                resultG.Clear(Color.White);
                //绘制缩略图
                resultG.DrawImage(initImage, new Rectangle(0, 0, side, side), new Rectangle(0, 0, initWidth, initHeight), GraphicsUnit.Pixel);

                //关键质量控制
                //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
                var icis = ImageCodecInfo.GetImageEncoders();
                ImageCodecInfo ici = null;
                foreach (var i in icis) if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif") ici = i;
                var ep = new EncoderParameters(1);
                ep.Param[0] = new EncoderParameter(Encoder.Quality, quality);

                //保存缩略图
                if (ici != null) resultImage.Save(fileSaveUrl, ici, ep);

                //释放关键质量控制所用资源
                ep.Dispose();

                //释放缩略图资源
                resultG.Dispose();
                resultImage.Dispose();

                //释放原始图片资源
                initImage.Dispose();
            }
        }

        #endregion

        #region 自定义裁剪并缩放

        /// <summary>
        /// 指定长宽裁剪
        /// 按模版比例最大范围的裁剪图片并缩放至模版尺寸
        /// </summary>
        /// <param name="fromFile">原图Stream对象</param>
        /// <param name="fileSaveUrl">保存路径</param>
        /// <param name="maxWidth">最大宽(单位:px)</param>
        /// <param name="maxHeight">最大高(单位:px)</param>
        /// <param name="quality">质量（范围0-100）</param>
        public static void CutForCustom(Stream fromFile, string fileSaveUrl, int maxWidth, int maxHeight, int quality)
        {
            //从文件获取原始图片，并使用流中嵌入的颜色管理信息
            var initImage = System.Drawing.Image.FromStream(fromFile, true);

            //原图宽高均小于模版，不作处理，直接保存
            if (initImage.Width <= maxWidth && initImage.Height <= maxHeight) initImage.Save(fileSaveUrl, ImageFormat.Jpeg);
            else
            {
                //模版的宽高比例
                var templateRate = (double)maxWidth/maxHeight;
                //原图片的宽高比例
                var initRate = (double)initImage.Width/initImage.Height;

                //原图与模版比例相等，直接缩放
                const double epsilon = 0;
                if (Math.Abs(templateRate - initRate) < epsilon)
                {
                    //按模版大小生成最终图片
                    System.Drawing.Image templateImage = new Bitmap(maxWidth, maxHeight);
                    var templateG = Graphics.FromImage(templateImage);
                    templateG.InterpolationMode = InterpolationMode.High;
                    templateG.SmoothingMode = SmoothingMode.HighQuality;
                    templateG.Clear(Color.White);
                    templateG.DrawImage(initImage, new Rectangle(0, 0, maxWidth, maxHeight), new Rectangle(0, 0, initImage.Width, initImage.Height), GraphicsUnit.Pixel);
                    templateImage.Save(fileSaveUrl, ImageFormat.Jpeg);
                }
                    //原图与模版比例不等，裁剪后缩放
                else
                {
                    //裁剪对象
                    System.Drawing.Image pickedImage;
                    Graphics pickedG;

                    //定位
                    var fromR = new Rectangle(0, 0, 0, 0); //原图裁剪定位
                    var toR = new Rectangle(0, 0, 0, 0); //目标定位

                    //宽为标准进行裁剪
                    if (templateRate > initRate)
                    {
                        //裁剪对象实例化
                        pickedImage = new Bitmap(initImage.Width, (int)Math.Floor(initImage.Width/templateRate));
                        pickedG = Graphics.FromImage(pickedImage);

                        //裁剪源定位
                        fromR.X = 0;
                        fromR.Y = (int)Math.Floor((initImage.Height - initImage.Width/templateRate)/2);
                        fromR.Width = initImage.Width;
                        fromR.Height = (int)Math.Floor(initImage.Width/templateRate);

                        //裁剪目标定位
                        toR.X = 0;
                        toR.Y = 0;
                        toR.Width = initImage.Width;
                        toR.Height = (int)Math.Floor(initImage.Width/templateRate);
                    }
                        //高为标准进行裁剪
                    else
                    {
                        pickedImage = new Bitmap((int)Math.Floor(initImage.Height*templateRate), initImage.Height);
                        pickedG = Graphics.FromImage(pickedImage);

                        fromR.X = (int)Math.Floor((initImage.Width - initImage.Height*templateRate)/2);
                        fromR.Y = 0;
                        fromR.Width = (int)Math.Floor(initImage.Height*templateRate);
                        fromR.Height = initImage.Height;

                        toR.X = 0;
                        toR.Y = 0;
                        toR.Width = (int)Math.Floor(initImage.Height*templateRate);
                        toR.Height = initImage.Height;
                    }

                    //设置质量
                    pickedG.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    pickedG.SmoothingMode = SmoothingMode.HighQuality;

                    //裁剪
                    pickedG.DrawImage(initImage, toR, fromR, GraphicsUnit.Pixel);

                    //按模版大小生成最终图片
                    System.Drawing.Image templateImage = new Bitmap(maxWidth, maxHeight);
                    var templateG = Graphics.FromImage(templateImage);
                    templateG.InterpolationMode = InterpolationMode.High;
                    templateG.SmoothingMode = SmoothingMode.HighQuality;
                    templateG.Clear(Color.White);
                    templateG.DrawImage(pickedImage, new Rectangle(0, 0, maxWidth, maxHeight), new Rectangle(0, 0, pickedImage.Width, pickedImage.Height), GraphicsUnit.Pixel);

                    //关键质量控制
                    //获取系统编码类型数组,包含了jpeg,bmp,png,gif,tiff
                    var icis = ImageCodecInfo.GetImageEncoders();
                    ImageCodecInfo ici = null;
                    foreach (var i in icis) if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif") ici = i;
                    var ep = new EncoderParameters(1);
                    ep.Param[0] = new EncoderParameter(Encoder.Quality, quality);

                    //保存缩略图
                    templateImage.Save(fileSaveUrl, ici, ep);
                    //templateImage.Save(fileSaveUrl, System.Drawing.Imaging.ImageFormat.Jpeg);

                    //释放资源
                    templateG.Dispose();
                    templateImage.Dispose();

                    pickedG.Dispose();
                    pickedImage.Dispose();
                }
            }

            //释放资源
            initImage.Dispose();
        }

        #endregion

        #region 等比缩放

        /// <summary>
        /// 图片等比缩放
        /// </summary>
        /// <param name="fromFile">原图Stream对象</param>
        /// <param name="savePath">缩略图存放地址</param>
        /// <param name="targetWidth">指定的最大宽度</param>
        /// <param name="targetHeight">指定的最大高度</param>
        /// <param name="watermarkText">水印文字(为""表示不使用水印)</param>
        /// <param name="watermarkImage">水印图片路径(为""表示不使用水印)</param>
        public static void ZoomAuto(Stream fromFile, string savePath, Double targetWidth, Double targetHeight, string watermarkText, string watermarkImage)
        {
            //创建目录
            var dir = Path.GetDirectoryName(savePath);
            if (dir != null && !Directory.Exists(dir)) Directory.CreateDirectory(dir);

            //原始图片（获取原始图片创建对象，并使用流中嵌入的颜色管理信息）
            var initImage = System.Drawing.Image.FromStream(fromFile, true);

            //原图宽高均小于模版，不作处理，直接保存
            if (initImage.Width <= targetWidth && initImage.Height <= targetHeight)
            {
                //文字水印
                if (watermarkText != "")
                {
                    using (var gWater = Graphics.FromImage(initImage))
                    {
                        var fontWater = new Font("黑体", 10);
                        Brush brushWater = new SolidBrush(Color.White);
                        gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);
                        gWater.Dispose();
                    }
                }

                //透明图片水印
                if (watermarkImage != "")
                {
                    if (File.Exists(watermarkImage))
                    {
                        //获取水印图片
                        using (var wrImage = System.Drawing.Image.FromFile(watermarkImage))
                        {
                            //水印绘制条件：原始图片宽高均大于或等于水印图片
                            if (initImage.Width >= wrImage.Width && initImage.Height >= wrImage.Height)
                            {
                                var gWater = Graphics.FromImage(initImage);

                                //透明属性
                                var imgAttributes = new ImageAttributes();
                                var colorMap = new ColorMap();
                                colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
                                colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
                                ColorMap[] remapTable = { colorMap };
                                imgAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);

                                float[][] colorMatrixElements = { new[]{ 1.0f, 0.0f, 0.0f, 0.0f, 0.0f }, new[]{ 0.0f, 1.0f, 0.0f, 0.0f, 0.0f }, new[]{ 0.0f, 0.0f, 1.0f, 0.0f, 0.0f }, new[]{ 0.0f, 0.0f, 0.0f, 0.5f, 0.0f }, //透明度:0.5
                                                                  new[]{ 0.0f, 0.0f, 0.0f, 0.0f, 1.0f } };

                                var wmColorMatrix = new ColorMatrix(colorMatrixElements);
                                imgAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
                                gWater.DrawImage(wrImage, new Rectangle(initImage.Width - wrImage.Width, initImage.Height - wrImage.Height, wrImage.Width, wrImage.Height), 0, 0, wrImage.Width, wrImage.Height, GraphicsUnit.Pixel, imgAttributes);

                                gWater.Dispose();
                            }
                            wrImage.Dispose();
                        }
                    }
                }

                //保存
                initImage.Save(savePath, ImageFormat.Jpeg);
            }
            else
            {
                //缩略图宽、高计算
                double newWidth = initImage.Width;
                double newHeight = initImage.Height;

                //宽大于高或宽等于高（横图或正方）
                if (initImage.Width > initImage.Height || initImage.Width == initImage.Height)
                {
                    //如果宽大于模版
                    if (initImage.Width > targetWidth)
                    {
                        //宽按模版，高按比例缩放
                        newWidth = targetWidth;
                        newHeight = initImage.Height*(targetWidth/initImage.Width);
                    }
                }
                    //高大于宽（竖图）
                else
                {
                    //如果高大于模版
                    if (initImage.Height > targetHeight)
                    {
                        //高按模版，宽按比例缩放
                        newHeight = targetHeight;
                        newWidth = initImage.Width*(targetHeight/initImage.Height);
                    }
                }

                //生成新图
                //新建一个bmp图片
                System.Drawing.Image newImage = new Bitmap((int)newWidth, (int)newHeight);
                //新建一个画板
                var newG = Graphics.FromImage(newImage);

                //设置质量
                newG.InterpolationMode = InterpolationMode.HighQualityBicubic;
                newG.SmoothingMode = SmoothingMode.HighQuality;

                //置背景色
                newG.Clear(Color.White);
                //画图
                newG.DrawImage(initImage, new Rectangle(0, 0, newImage.Width, newImage.Height), new Rectangle(0, 0, initImage.Width, initImage.Height), GraphicsUnit.Pixel);

                //文字水印
                if (watermarkText != "")
                {
                    using (var gWater = Graphics.FromImage(newImage))
                    {
                        var fontWater = new Font("宋体", 10);
                        Brush brushWater = new SolidBrush(Color.White);
                        gWater.DrawString(watermarkText, fontWater, brushWater, 10, 10);
                        gWater.Dispose();
                    }
                }

                //透明图片水印
                if (watermarkImage != "")
                {
                    if (File.Exists(watermarkImage))
                    {
                        //获取水印图片
                        using (var wrImage = System.Drawing.Image.FromFile(watermarkImage))
                        {
                            //水印绘制条件：原始图片宽高均大于或等于水印图片
                            if (newImage.Width >= wrImage.Width && newImage.Height >= wrImage.Height)
                            {
                                var gWater = Graphics.FromImage(newImage);

                                //透明属性
                                var imgAttributes = new ImageAttributes();
                                var colorMap = new ColorMap();
                                colorMap.OldColor = Color.FromArgb(255, 0, 255, 0);
                                colorMap.NewColor = Color.FromArgb(0, 0, 0, 0);
                                ColorMap[] remapTable = { colorMap };
                                imgAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);

                                float[][] colorMatrixElements = { new[]{ 1.0f, 0.0f, 0.0f, 0.0f, 0.0f }, new[]{ 0.0f, 1.0f, 0.0f, 0.0f, 0.0f }, new[]{ 0.0f, 0.0f, 1.0f, 0.0f, 0.0f }, new[]{ 0.0f, 0.0f, 0.0f, 0.5f, 0.0f }, //透明度:0.5
                                                                  new[]{ 0.0f, 0.0f, 0.0f, 0.0f, 1.0f } };

                                var wmColorMatrix = new ColorMatrix(colorMatrixElements);
                                imgAttributes.SetColorMatrix(wmColorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
                                gWater.DrawImage(wrImage, new Rectangle(newImage.Width - wrImage.Width, newImage.Height - wrImage.Height, wrImage.Width, wrImage.Height), 0, 0, wrImage.Width, wrImage.Height, GraphicsUnit.Pixel, imgAttributes);
                                gWater.Dispose();
                            }
                            wrImage.Dispose();
                        }
                    }
                }

                //保存缩略图
                newImage.Save(savePath, ImageFormat.Jpeg);

                //释放资源
                newG.Dispose();
                newImage.Dispose();
                initImage.Dispose();
            }
        }

        #endregion

        #region 其它

        /// <summary>
        /// 判断文件类型是否为WEB格式图片
        /// (注：JPG,GIF,BMP,PNG)
        /// </summary>
        /// <param name="contentType">HttpPostedFile.ContentType</param>
        /// <returns></returns>
        public static bool IsWebImage(string contentType) {
            return contentType == "image/pjpeg" || contentType == "image/jpeg" || contentType == "image/gif" || contentType == "image/bmp" || contentType == "image/png";
        }

        #endregion
    }