C#对图片的几种简单处理

(1)如何获取.gif图片中的各个帧？ 
(2)如何获取图片的缩略图？ 
(3)如何“截取”图片的指定区域？ 

using System.Drawing;using System.Drawing.Drawing2D;using System.Drawing.Imaging;public class ImageHelper{    /// <summary>    /// 获取图片中的各帧    /// </summary>    /// <param name="pPath">图片路径</param>    /// <param name="pSavePath">保存路径</param>    public void GetFrames(string pPath, string pSavedPath)    {        Image gif = Image.FromFile(pPath);        FrameDimension fd = new FrameDimension(gif.FrameDimensionsList[0]);        //获取帧数(gif图片可能包含多帧，其它格式图片一般仅一帧)        int count = gif.GetFrameCount(fd);        //以Jpeg格式保存各帧        for (int i = 0; i < count; i++)        {            gif.SelectActiveFrame(fd, i);            gif.Save(pSavedPath + "//frame_" + i + ".jpg", ImageFormat.Jpeg);        }    }    /// <summary>    /// 获取图片缩略图    /// </summary>    /// <param name="pPath">图片路径</param>    /// <param name="pSavePath">保存路径</param>    /// <param name="pWidth">缩略图宽度</param>    /// <param name="pHeight">缩略图高度</param>    /// <param name="pFormat">保存格式，通常可以是jpeg</param>    public void GetSmaller(string pPath, string pSavedPath, int pWidth, int pHeight)    {        try        {            Image smallerImg;            Image originalImg = Image.FromFile(pPath);            Image.GetThumbnailImageAbort callback = new Image.GetThumbnailImageAbort(ThumbnailCallback);            smallerImg = originalImg.GetThumbnailImage(pWidth, pHeight, callback, IntPtr.Zero);            smallerImg.Save(pSavedPath + "//smaller.jpg", ImageFormat.Jpeg);        }        catch (Exception x)        {            //        }    }    /// <summary>    /// 获取图片指定部分    /// </summary>    /// <param name="pPath">图片路径</param>    /// <param name="pSavePath">保存路径</param>    /// <param name="pPartStartPointX">目标图片开始绘制处的坐标X值(通常为)</param>    /// <param name="pPartStartPointY">目标图片开始绘制处的坐标Y值(通常为)</param>    /// <param name="pPartWidth">目标图片的宽度</param>    /// <param name="pPartHeight">目标图片的高度</param>    /// <param name="pOrigStartPointX">原始图片开始截取处的坐标X值</param>    /// <param name="pOrigStartPointY">原始图片开始截取处的坐标Y值</param>    /// <param name="pFormat">保存格式，通常可以是jpeg</param>    public void GetPart(string pPath, string pSavedPath, int pPartStartPointX, int pPartStartPointY, int pPartWidth, int pPartHeight, int pOrigStartPointX, int pOrigStartPointY)    {        Image originalImg = Image.FromFile(pPath);        Bitmap partImg = new Bitmap(pPartWidth, pPartHeight);        Graphics graphics = Graphics.FromImage(partImg);        Rectangle destRect = new Rectangle(new Point(pPartStartPointX, pPartStartPointY), new Size(pPartWidth, pPartHeight));//目标位置        Rectangle origRect = new Rectangle(new Point(pOrigStartPointX, pOrigStartPointY), new Size(pPartWidth, pPartHeight));//原图位置（默认从原图中截取的图片大小等于目标图片的大小）        graphics.DrawImage(originalImg, destRect, origRect, GraphicsUnit.Pixel);        partImg.Save(pSavedPath + "//part.jpg", ImageFormat.Jpeg);    }    public bool ThumbnailCallback()    {        return false;    }}