图片缩放代码

using System;

using System.Collections.Generic;

using System.Text;

using System.IO;

using System.Drawing;

using System.Drawing.Drawing2D;

using System.Drawing.Imaging;



namespace WuJian.Common

{

    /// <summary>

    /// 图片处理

    /// http://www.cnblogs.com/wu-jian/

    /// 

    /// 吴剑 2011-02-20 创建

    /// 吴剑 2012-08-08 修改

    /// </summary>

    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>

        /// <remarks>吴剑 2012-08-08</remarks>

        /// <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(System.IO.Stream fromFile, string fileSaveUrl, int side, int quality)

        {

            //创建目录

            string dir = Path.GetDirectoryName(fileSaveUrl);

            if (!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）

            System.Drawing.Image 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, System.Drawing.Imaging.ImageFormat.Jpeg);

            }

            else

            {

                //原始图片的宽、高

                int initWidth = initImage.Width;

                int 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 = null;

                    System.Drawing.Graphics pickedG = null;



                    //宽大于高的横图

                    if (initWidth > initHeight)

                    {

                        //对象实例化

                        pickedImage = new System.Drawing.Bitmap(initHeight, initHeight);

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);

                        //设置质量

                        pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

                        pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                        //定位

                        Rectangle fromR = new Rectangle((initWidth - initHeight) / 2, 0, initHeight, initHeight);

                        Rectangle toR = new Rectangle(0, 0, initHeight, initHeight);

                        //画图

                        pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);

                        //重置宽

                        initWidth = initHeight;

                    }

                    //高大于宽的竖图

                    else

                    {

                        //对象实例化

                        pickedImage = new System.Drawing.Bitmap(initWidth, initWidth);

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);

                        //设置质量

                        pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

                        pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                        //定位

                        Rectangle fromR = new Rectangle(0, (initHeight - initWidth) / 2, initWidth, initWidth);

                        Rectangle toR = new Rectangle(0, 0, initWidth, initWidth);

                        //画图

                        pickedG.DrawImage(initImage, toR, fromR, System.Drawing.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 System.Drawing.Bitmap(side, side);

                System.Drawing.Graphics resultG = System.Drawing.Graphics.FromImage(resultImage);

                //设置质量

                resultG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

                resultG.SmoothingMode = System.Drawing.Drawing2D.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 System.Drawing.Rectangle(0, 0, side, side), new System.Drawing.Rectangle(0, 0, initWidth, initHeight), System.Drawing.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

                ImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();

                ImageCodecInfo ici = null;

                foreach (ImageCodecInfo i in icis)

                {

                    if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif")

                    {

                        ici = i;

                    }

                }

                EncoderParameters ep = new EncoderParameters(1);

                ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)quality);



                //保存缩略图

                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>

        /// <remarks>吴剑 2012-08-08</remarks>

        /// <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(System.IO.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

            System.Drawing.Image 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, System.Drawing.Imaging.ImageFormat.Jpeg);

            }

            else

            {

                //模版的宽高比例

                double templateRate = (double)maxWidth / maxHeight;

                //原图片的宽高比例

                double initRate = (double)initImage.Width / initImage.Height;



                //原图与模版比例相等，直接缩放

                if (templateRate == initRate)

                {

                    //按模版大小生成最终图片

                    System.Drawing.Image templateImage = new System.Drawing.Bitmap(maxWidth, maxHeight);

                    System.Drawing.Graphics templateG = System.Drawing.Graphics.FromImage(templateImage);

                    templateG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

                    templateG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                    templateG.Clear(Color.White);

                    templateG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, maxWidth, maxHeight), new System.Drawing.Rectangle(0, 0, initImage.Width, initImage.Height), System.Drawing.GraphicsUnit.Pixel);

                    templateImage.Save(fileSaveUrl, System.Drawing.Imaging.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 = null;

                    System.Drawing.Graphics pickedG = null;



                    //定位

                    Rectangle fromR = new Rectangle(0, 0, 0, 0);//原图裁剪定位

                    Rectangle 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 System.Drawing.Bitmap(initImage.Width, (int)System.Math.Floor(initImage.Width / templateRate));

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);



                        //裁剪源定位

                        fromR.X = 0;

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

                        fromR.Width = initImage.Width;

                        fromR.Height = (int)System.Math.Floor(initImage.Width / templateRate);



                        //裁剪目标定位

                        toR.X = 0;

                        toR.Y = 0;

                        toR.Width = initImage.Width;

                        toR.Height = (int)System.Math.Floor(initImage.Width / templateRate);

                    }

                    //高为标准进行裁剪

                    else

                    {

                        pickedImage = new System.Drawing.Bitmap((int)System.Math.Floor(initImage.Height * templateRate), initImage.Height);

                        pickedG = System.Drawing.Graphics.FromImage(pickedImage);



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

                        fromR.Y = 0;

                        fromR.Width = (int)System.Math.Floor(initImage.Height * templateRate);

                        fromR.Height = initImage.Height;



                        toR.X = 0;

                        toR.Y = 0;

                        toR.Width = (int)System.Math.Floor(initImage.Height * templateRate);

                        toR.Height = initImage.Height;

                    }



                    //设置质量

                    pickedG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

                    pickedG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;



                    //裁剪

                    pickedG.DrawImage(initImage, toR, fromR, System.Drawing.GraphicsUnit.Pixel);



                    //按模版大小生成最终图片

                    System.Drawing.Image templateImage = new System.Drawing.Bitmap(maxWidth, maxHeight);

                    System.Drawing.Graphics templateG = System.Drawing.Graphics.FromImage(templateImage);

                    templateG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

                    templateG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                    templateG.Clear(Color.White);

                    templateG.DrawImage(pickedImage, new System.Drawing.Rectangle(0, 0, maxWidth, maxHeight), new System.Drawing.Rectangle(0, 0, pickedImage.Width, pickedImage.Height), System.Drawing.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

                    ImageCodecInfo[] icis = ImageCodecInfo.GetImageEncoders();

                    ImageCodecInfo ici = null;

                    foreach (ImageCodecInfo i in icis)

                    {

                        if (i.MimeType == "image/jpeg" || i.MimeType == "image/bmp" || i.MimeType == "image/png" || i.MimeType == "image/gif")

                        {

                            ici = i;

                        }

                    }

                    EncoderParameters ep = new EncoderParameters(1);

                    ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)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>

        /// <remarks>吴剑 2012-08-08</remarks>

        /// <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(System.IO.Stream fromFile, string savePath, System.Double targetWidth, System.Double targetHeight, string watermarkText, string watermarkImage)

        {

            //创建目录

            string dir = Path.GetDirectoryName(savePath);

            if (!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）

            System.Drawing.Image 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 (System.Drawing.Graphics gWater = System.Drawing.Graphics.FromImage(initImage))

                    {

                        System.Drawing.Font fontWater = new Font("黑体", 10);

                        System.Drawing.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 (System.Drawing.Image 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)

                            {

                                Graphics gWater = Graphics.FromImage(initImage);



                                //透明属性

                                ImageAttributes imgAttributes = new ImageAttributes();

                                ColorMap 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 float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},

                                   new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},

                                   new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},

                                   new float[] {0.0f,  0.0f,  0.0f,  0.5f, 0.0f},//透明度:0.5

                                   new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}

                                };



                                ColorMatrix 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, System.Drawing.Imaging.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 System.Drawing.Bitmap((int)newWidth, (int)newHeight);

                //新建一个画板

                System.Drawing.Graphics newG = System.Drawing.Graphics.FromImage(newImage);



                //设置质量

                newG.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;

                newG.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;



                //置背景色

                newG.Clear(Color.White);

                //画图

                newG.DrawImage(initImage, new System.Drawing.Rectangle(0, 0, newImage.Width, newImage.Height), new System.Drawing.Rectangle(0, 0, initImage.Width, initImage.Height), System.Drawing.GraphicsUnit.Pixel);



                //文字水印

                if (watermarkText != "")

                {

                    using (System.Drawing.Graphics gWater = System.Drawing.Graphics.FromImage(newImage))

                    {

                        System.Drawing.Font fontWater = new Font("宋体", 10);

                        System.Drawing.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 (System.Drawing.Image 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)

                            {

                                Graphics gWater = Graphics.FromImage(newImage);



                                //透明属性

                                ImageAttributes imgAttributes = new ImageAttributes();

                                ColorMap 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 float[] {1.0f,  0.0f,  0.0f,  0.0f, 0.0f},

                                   new float[] {0.0f,  1.0f,  0.0f,  0.0f, 0.0f},

                                   new float[] {0.0f,  0.0f,  1.0f,  0.0f, 0.0f},

                                   new float[] {0.0f,  0.0f,  0.0f,  0.5f, 0.0f},//透明度:0.5

                                   new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}

                                };



                                ColorMatrix 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, System.Drawing.Imaging.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)

        {

            if (contentType == "image/pjpeg" || contentType == "image/jpeg" || contentType == "image/gif" || contentType == "image/bmp" || contentType == "image/png")

            {

                return true;

            }

            else

            {

                return false;

            }

        }



        #endregion



    }//end class

}

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