winform程序，如何控制USB摄像头的像素？？？
现已实现抓图的功能，照相后图片保存到一个固定的路径下，叫一个固定的名称，比如：C：/image.jpg.或者是C：/image.bmp
问题是，保存的图片竟然是901KB...这样的话，我想要把图片存入数据库就会超出字段范围。
如何才能让其保存的图片为100KB以内？（就是系统图片那么大也才100KB不到的）
一下是代码：
cam类：
using System;using System.Collections.Generic;using System.Text;using System.Runtime.InteropServices;namespace PlatForm{ //参考AVICap技术 public class Cam { 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 IntPtr hWndC; private IntPtr mControlPtr; private bool bWorkStart = false; private int mWidth; private int mHeight; private int mLeft; private int mTop; /// <summary> /// 初始化显示图像 /// </summary> /// <param name="handle">控件的句柄 </param> /// <param name="left">开始显示的左边距 </param> /// <param name="top">开始显示的上边距 </param> /// <param name="width">要显示的宽度 </param> /// <param name="height">要显示的长度 </param> public Cam(IntPtr handle, int left, int top, int width, int height) { mControlPtr = handle; mWidth = width; mHeight = height; mLeft = left; mTop = top; } //如果该函数调用成功 则函数返回窗口的句柄 否则函数返回NULL。 [DllImport("avicap32.dll")] private static extern IntPtr capCreateCaptureWindowA(byte[] lpszWindowName, int dwStyle, int x, int y, int nWidth, int nHeight, IntPtr hWndParent, int nID); // 视频格式设置对话框 //BOOL capDlgVideoFormat( hwnd ); // hwnd：捕捉窗口句柄 //视频格式设置对话框对于每一个捕捉驱动程序来说，是唯一的。而且，有些驱动程序不一定支持这一功能。应用程序可以通过检测CAPDRIVERCAPS结构的成员变量fHasDlgVideoFormat来判断驱动程序是否支持这一功能。 [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, IntPtr wParam, IntPtr lParam); /// <summary> /// 开始显示图像 /// </summary> public void Start() { if (bWorkStart) { return; } bWorkStart = true; byte[] lpszName = new byte[100]; hWndC = capCreateCaptureWindowA(lpszName, WS_CHILD | WS_VISIBLE, mLeft, mTop, mWidth, mHeight, mControlPtr, 0); if (hWndC.ToInt32() != 0) { SendMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, IntPtr.Zero, IntPtr.Zero); SendMessage(hWndC, WM_CAP_SET_CALLBACK_ERROR, IntPtr.Zero, IntPtr.Zero); SendMessage(hWndC, WM_CAP_SET_CALLBACK_STATUSA, IntPtr.Zero, IntPtr.Zero); SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, IntPtr.Zero, IntPtr.Zero); SendMessage(hWndC, WM_CAP_SET_SCALE, (IntPtr)1, IntPtr.Zero); SendMessage(hWndC, WM_CAP_SET_PREVIEWRATE, (IntPtr)66, IntPtr.Zero); SendMessage(hWndC, WM_CAP_SET_OVERLAY, (IntPtr)1, IntPtr.Zero); SendMessage(hWndC, WM_CAP_SET_PREVIEW, (IntPtr)1, IntPtr.Zero); } return; } /// <summary> /// 停止显示图像 /// </summary> public void Stop() { SendMessage(hWndC, WM_CAP_DRIVER_DISCONNECT, IntPtr.Zero, IntPtr.Zero); bWorkStart = false; } /// <summary> /// 抓图 /// </summary> /// <param name="path">要保存bmp文件的路径 </param> public void GrabImage(string path) { IntPtr hBmp = Marshal.StringToHGlobalAnsi(path); //将System.String内容复制到非托管内存当中 SendMessage(hWndC, WM_CAP_SAVEDIB, IntPtr.Zero, hBmp); } ///<summary> ///录像 ///</summary> ///<param name="path">要保存avi文件的路径</param> public void Kinescope(string path) { IntPtr hCap = Marshal.StringToHGlobalAnsi(path); SendMessage(hWndC, WM_CAP_FILE_SET_CAPTURE_FILEA, IntPtr.Zero, hCap); SendMessage(hWndC, WM_CAP_SEQUENCE, IntPtr.Zero, hCap); } ///<summary> ///停止录像 ///</summary> public void StopKinescope() { SendMessage(hWndC, WM_CAP_STOP, IntPtr.Zero, IntPtr.Zero); } }}