/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="fileName">原图路径</param>
/// <param name="newFile">缩略图路径</param>
/// <param name="maxHeight">最大高度</param>
/// <param name="maxWidth">最大宽度</param>
public string ThumbnailImage(string fileName, string newFile, int maxHeight, int maxWidth)
{System.Drawing.Image img = System.Drawing.Image.FromFile(fileName);System.Drawing.Imaging.ImageFormat thisFormat = img.RawFormat;//缩略图尺寸double w = 0.0;double h = 0.0;double sw = Convert.ToDouble(img.Width);double sh = Convert.ToDouble(img.Height);double mw = Convert.ToDouble(maxWidth);double mh = Convert.ToDouble(maxHeight);if (sw < mw && sh < mh){w = sw;h = sh;}else if ((sw / sh) > (mw / mh)){w = maxWidth;h = (w * sh) / sw;}else{h = maxHeight;w = (h * sw) / sh;}Size newSize = new Size(Convert.ToInt32(w), Convert.ToInt32(h));Bitmap outBmp = new Bitmap(newSize.Width, newSize.Height);Graphics g = Graphics.FromImage(outBmp);//设置画布的描绘质量g.CompositingQuality = CompositingQuality.HighQuality;g.SmoothingMode = SmoothingMode.HighQuality;g.InterpolationMode = InterpolationMode.HighQualityBicubic;g.DrawImage(img, new Rectangle(0, 0, newSize.Width, newSize.Height), 0, 0, img.Width, img.Height, GraphicsUnit.Pixel);g.Dispose();//以下代码为保存图片时,设置压缩质量EncoderParameters encoderParams = new EncoderParameters();long[] quality = new long[1];quality[0] = 100;EncoderParameter encoderParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, quality);encoderParams.Param[0] = encoderParam;//获得包含有关内置图像编码解码器的信息的ImageCodecInfo 对象.ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();ImageCodecInfo jpegICI = null;for (int x = 0; x < arrayICI.Length;x++){if (arrayICI[x].FormatDescription.Equals("JPEG")){jpegICI = arrayICI[x];//设置JPEG编码break;}}if (jpegICI != null){Bitmap newbit = new Bitmap(outBmp);newbit.Save(newFile, jpegICI, encoderParams);}else{outBmp.Save(newFile,thisFormat);}img.Dispose();outBmp.Dispose();return newFile;
}