C# 图片水印类

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

public class ImageWaterMark
    {
        /// <summary>
        /// 图片水印
        /// </summary>
        /// <param name="img">图片</param>
        /// <param name="filename">保存文件名</param>
        /// <param name="watermarkFilename">水印文件名</param>
        /// <param name="watermarkStatus">图片水印位置 0=不使用 1=左上 2=中上 3=右上 4=左中  9=右下</param>
        /// <param name="quality">附加水印图片质量,0-100</param>
        /// <param name="watermarkTransparency">水印的透明度 1--10 10为不透明</param>
        public static void AddImageSignPic(Image img, string filename, string watermarkFilename, int watermarkStatus, int quality, int watermarkTransparency)
        {
            Graphics g = Graphics.FromImage(img);
            //设置高质量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
            //设置高质量,低速度呈现平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            Image watermark = new Bitmap(watermarkFilename);
            if (watermark.Height >= img.Height || watermark.Width >= img.Width)
            {
                return;
            }
            ImageAttributes imageAttributes = 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 };
            imageAttributes.SetRemapTable(remapTable, ColorAdjustType.Bitmap);
            float transparency = 0.5F;
            if (watermarkTransparency >= 1 && watermarkTransparency <= 10)
            {
                transparency = (watermarkTransparency / 10.0F);
            }
            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,  transparency, 0.0f},
                                                new float[] {0.0f,  0.0f,  0.0f,  0.0f, 1.0f}
                                            };
            ColorMatrix colorMatrix = new ColorMatrix(colorMatrixElements);
            imageAttributes.SetColorMatrix(colorMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
            int xpos = 0;
            int ypos = 0;
            switch (watermarkStatus)
            {
                case 1:
                    xpos = (int)(img.Width * (float).01);
                    ypos = (int)(img.Height * (float).01);
                    break;
                case 2:
                    xpos = (int)((img.Width * (float).50) - (watermark.Width / 2));
                    ypos = (int)(img.Height * (float).01);
                    break;
                case 3:
                    xpos = (int)((img.Width * (float).99) - (watermark.Width));
                    ypos = (int)(img.Height * (float).01);
                    break;
                case 4:
                    xpos = (int)(img.Width * (float).01);
                    ypos = (int)((img.Height * (float).50) - (watermark.Height / 2));
                    break;
                case 5:
                    xpos = (int)((img.Width * (float).50) - (watermark.Width / 2));
                    ypos = (int)((img.Height * (float).50) - (watermark.Height / 2));
                    break;
                case 6:
                    xpos = (int)((img.Width * (float).99) - (watermark.Width));
                    ypos = (int)((img.Height * (float).50) - (watermark.Height / 2));
                    break;
                case 7:
                    xpos = (int)(img.Width * (float).01);
                    ypos = (int)((img.Height * (float).99) - watermark.Height);
                    break;
                case 8:
                    xpos = (int)((img.Width * (float).50) - (watermark.Width / 2));
                    ypos = (int)((img.Height * (float).99) - watermark.Height);
                    break;
                case 9:
                    xpos = (int)((img.Width * (float).99) - (watermark.Width));
                    ypos = (int)((img.Height * (float).99) - watermark.Height);
                    break;
            }
            g.DrawImage(watermark, new Rectangle(xpos, ypos, watermark.Width, watermark.Height), 0, 0, watermark.Width, watermark.Height, GraphicsUnit.Pixel, imageAttributes);
            //g.DrawImage(watermark, new System.Drawing.Rectangle(xpos, ypos, watermark.Width, watermark.Height), 0, 0, watermark.Width, watermark.Height, System.Drawing.GraphicsUnit.Pixel);
            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
            ImageCodecInfo ici = null;
            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.MimeType.IndexOf("jpeg") > -1)
                {
                    ici = codec;
                }
            }
            EncoderParameters encoderParams = new EncoderParameters();
            long[] qualityParam = new long[1];
            if (quality < 0 || quality > 100)
            {
                quality = 80;
            }
            qualityParam[0] = quality;
            EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qualityParam);
            encoderParams.Param[0] = encoderParam;
            if (ici != null)
            {
                img.Save(filename, ici, encoderParams);
            }
            else
            {
                img.Save(filename);
            }
            g.Dispose();
            img.Dispose();
            watermark.Dispose();
            imageAttributes.Dispose();
        }

        /// <summary>
        /// 文字水印
        /// </summary>
        /// <param name="img">图片</param>
        /// <param name="filename">保存文件名</param>
        /// <param name="watermarkText">水印文字</param>
        /// <param name="watermarkStatus">图片水印位置 0=不使用 1=左上 2=中上 3=右上 4=左中  9=右下</param>
        /// <param name="quality">附加水印图片质量,0-100</param>
        /// <param name="fontname">字体</param>
        /// <param name="fontsize">字体大小</param>
        public static void AddImageSignText(Image img, string filename, string watermarkText, int watermarkStatus, int quality, string fontname, int fontsize)
        {
            Graphics g = Graphics.FromImage(img);
            Font drawFont = new Font(fontname, fontsize, FontStyle.Regular, GraphicsUnit.Pixel);
            SizeF crSize;
            crSize = g.MeasureString(watermarkText, drawFont);
            float xpos = 0;
            float ypos = 0;
            switch (watermarkStatus)
            {
                case 1:
                    xpos = (float)img.Width * (float).01;
                    ypos = (float)img.Height * (float).01;
                    break;
                case 2:
                    xpos = ((float)img.Width * (float).50) - (crSize.Width / 2);
                    ypos = (float)img.Height * (float).01;
                    break;
                case 3:
                    xpos = ((float)img.Width * (float).99) - crSize.Width;
                    ypos = (float)img.Height * (float).01;
                    break;
                case 4:
                    xpos = (float)img.Width * (float).01;
                    ypos = ((float)img.Height * (float).50) - (crSize.Height / 2);
                    break;
                case 5:
                    xpos = ((float)img.Width * (float).50) - (crSize.Width / 2);
                    ypos = ((float)img.Height * (float).50) - (crSize.Height / 2);
                    break;
                case 6:
                    xpos = ((float)img.Width * (float).99) - crSize.Width;
                    ypos = ((float)img.Height * (float).50) - (crSize.Height / 2);
                    break;
                case 7:
                    xpos = (float)img.Width * (float).01;
                    ypos = ((float)img.Height * (float).99) - crSize.Height;
                    break;
                case 8:
                    xpos = ((float)img.Width * (float).50) - (crSize.Width / 2);
                    ypos = ((float)img.Height * (float).99) - crSize.Height;
                    break;
                case 9:
                    xpos = ((float)img.Width * (float).99) - crSize.Width;
                    ypos = ((float)img.Height * (float).99) - crSize.Height;
                    break;
            }
            g.DrawString(watermarkText, drawFont, new SolidBrush(Color.White), xpos + 1, ypos + 1);
            g.DrawString(watermarkText, drawFont, new SolidBrush(Color.Black), xpos, ypos);
            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
            ImageCodecInfo ici = null;
            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.MimeType.IndexOf("jpeg") > -1)
                {
                    ici = codec;
                }
            }
            EncoderParameters encoderParams = new EncoderParameters();
            long[] qualityParam = new long[1];
            if (quality < 0 || quality > 100)
            {
                quality = 80;
            }
            qualityParam[0] = quality;
            EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qualityParam);
            encoderParams.Param[0] = encoderParam;
            if (ici != null)
            {
                img.Save(filename, ici, encoderParams);
            }
            else
            {
                img.Save(filename);
            }
            g.Dispose();
            //bmp.Dispose();
            img.Dispose();
        }
    }

调用：

System.Drawing.Image img = System.Drawing.Image.FromStream(InputFile1.PostedFile.InputStream);//用上传控件加载图片
            //System.Drawing.Image img = System.Drawing.Image.FromFile(Server.MapPath("~/bb.jpg"));//用加字件加载图片

            string fileName = Server.MapPath("~/aa.jpg");
            string waterName = Server.MapPath("~/water.jpg");

            //图片水印
            ImageWaterMark.AddImageSignPic(img, fileName, waterName, 3, 80, 6);
            //文字水印
            //ImageWaterMark.AddImageSignText(img, fileName, "水印测试", 3, 100, "宋体", 12);