c# 图片加水印

        /// <summary>
        /// 图片水印
        /// </summary>
        /// <param name="imgpath">服务器图片相对路径</param>
        /// <param name="filename">保存文件名</param>
        /// <param name="watermarkfilename">水印文件相对路径</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(string imgpath, string filename, string watermarkfilename, int watermarkstatus, int quality, int watermarktransparency)
        {
            if (!file.exists(utils.getmappath(imgpath)))
                return;
            byte[] _imagebytes = file.readallbytes(utils.getmappath(imgpath));
            image img = image.fromstream(new system.io.memorystream(_imagebytes));
            filename = utils.getmappath(filename);

            if (watermarkfilename.startswith("/") == false)
                watermarkfilename = "/" + watermarkfilename;
            watermarkfilename = utils.getmappath(watermarkfilename);
            if (!file.exists(watermarkfilename))
                return;
            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);

            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="imgpath">服务器图片相对路径</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(string imgpath, string filename, string watermarktext, int watermarkstatus, int quality, string fontname, int fontsize)
        {
            byte[] _imagebytes = file.readallbytes(utils.getmappath(imgpath));
            image img = image.fromstream(new system.io.memorystream(_imagebytes));
            filename = utils.getmappath(filename);

            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();
            img.dispose();
        }