C#拍照后怎么改变分辨率？
我用的是这个调用摄像头的类：
using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;
using System.Runtime.InteropServices;

namespace WindowsApplication6
{
  /// <summary>  
  /// 一个控制摄像头的类  
  /// </summary>  
  public class cVideo
  {
  //导入API函数
  [DllImport("avicap32.dll")]
  private static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID);
  [DllImport("avicap32.dll")]
  private static extern int capGetVideoFormat(IntPtr hWnd, IntPtr psVideoFormat, int wSize);
  [DllImport("User32.dll")]
  private static extern bool SendMessage(IntPtr hWnd, int wMsg, int wParam, int lParam);
  //常量设置
  private const int WM_USER = 0x400;
  private const int WS_CHILD = 0x40000000;
  private const int WS_VISIBLE = 0x10000000;
  private const int WM_CAP_START = WM_USER;
  private const int WM_CAP_STOP = WM_CAP_START + 68;
  private const int WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10;
  private const int WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11;
  private const int WM_CAP_SAVEDIB = WM_CAP_START + 25;
  private const int WM_CAP_GRAB_FRAME = WM_CAP_START + 60;
  private const int WM_CAP_SEQUENCE = WM_CAP_START + 62;
  private const int WM_CAP_FILE_SET_CAPTURE_FILEA = WM_CAP_START + 20;
  private const int WM_CAP_SEQUENCE_NOFILE = WM_CAP_START + 63;
  private const int WM_CAP_SET_OVERLAY = WM_CAP_START + 51;
  private const int WM_CAP_SET_PREVIEW = WM_CAP_START + 50;
  private const int WM_CAP_SET_CALLBACK_VIDEOSTREAM = WM_CAP_START + 6;
  private const int WM_CAP_SET_CALLBACK_ERROR = WM_CAP_START + 2;
  private const int WM_CAP_SET_CALLBACK_STATUSA = WM_CAP_START + 3;
  private const int WM_CAP_SET_CALLBACK_FRAME = WM_CAP_START + 5;
  private const int WM_CAP_SET_SCALE = WM_CAP_START + 53;
  private const int WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52;
  private const int WM_CAP_FILE_SAVEAS = WM_CAP_START + 23; //将捕捉文件保存为另一个用户指定的文件。这个消息不会改变捕捉文件的名字和内容,

  //全局变量
  private IntPtr hWndC;　//句柄
  private IntPtr mControlPtr;　//句柄
  private bool bWorkStart = false;
  private int mWidth;　　//视频显示宽度
  private int mHeight; //视频显示高度
  private int mLeft; //视频显示左边距
  private int mTop; //视频显示上边距
  /// <summary>  
  /// 初始化显示图像  
  /// </summary>  
  /// <param name="handle">播放视频控件的句柄</param>  
  /// <param name="left">视频显示的左边距</param>  
  /// <param name="top">视频显示的上边距</param>
  /// <param name="down">视频显示的下边距</param>
  /// <param name="right">视频显示的右边距</param>
  /// <param name="width">要显示视频的宽度</param>  
  /// <param name="height">要显示视频的长度</param>  
  public cVideo(IntPtr handle, int left, int top, int width, int height)
  {
  mControlPtr = handle;