如何设置网络摄像头的分辨率

问题描述

我想设置网络摄像头的分辨率。

我的代码是

I want to set resolution of web cam.
My code is

[StructLayout(LayoutKind.Sequential)]
public struct BITMAPINFOHEADER
{
public uint biSize;
public int biWidth;
public int biHeight;
public ushort biPlanes;
public ushort biBitCount;
public uint biCompression;
public uint biSizeImage;
public int biXPelsPerMeter;
public int biYPelsPerMeter;
public uint biClrUsed;
public uint biClrImportant;
}
[StructLayout(LayoutKind.Sequential)]
public struct BITMAPINFO
{
public BITMAPINFOHEADER bmiHeader;
public int bmiColors;
}
public class Avicap32
{
[DllImport("avicap32.dll")]
public extern static IntPtr capGetDriverDescription(ushort index, StringBuilder name, int nameCapacity, StringBuilder description, int descriptionCapacity);
[DllImport("avicap32.dll")]
public extern static IntPtr capCreateCaptureWindow(string title, uint style, int x, int y, int width, int height, IntPtr window, int id);
[DllImport("avicap32.dll")]
public extern static bool capDriverGetName(IntPtr deviceHandle, StringBuilder Drivername, byte size);
[DllImport("avicap32.dll")]
public extern static UInt32 capGetVideoFormat(IntPtr deviceHandle,ref  BITMAPINFO m_bitmapinfo, byte size);
[DllImport("avicap32.dll")]
public extern static bool capSetVideoFormat(IntPtr deviceHandle,ref BITMAPINFO m_bitmapinfo, byte size);
[DllImport("avicap32.dll" ,EntryPoint="capCaptureAbort")]
public extern static bool capCaptureAbort(IntPtr deviceHandle);
[DllImport("avicap32.dll" ,EntryPoint="capCaptureStop")]
public extern static bool capCaptureStop(IntPtr deviceHandle);
public class Constants
{
public const uint WM_CAP = 0x400;
public const uint WM_CAP_DRIVER_CONNECT = 0x40a;
public const uint WM_CAP_DRIVER_DISCONNECT = 0x40b;
public const uint WM_CAP_EDIT_COPY = 0x41e;
public const uint WM_CAP_SET_PREVIEW = 0x432;
public const uint WM_CAP_SET_OVERLAY = 0x433;
public const uint WM_CAP_SET_PREVIEWRATE = 0x434;
public const uint WM_CAP_SET_SCALE = 0x435;
public const uint WS_CHILD = 0x40000000;
public const uint WS_VISIBLE = 0x10000000;
}
public   const int WM_CAP_START = 1024; // WM_USER
public const int WM_CAP_SET_CALLBACK_FRAME = WM_CAP_START + 5;
public const int WM_CAP_DRIVER_CONNECT = WM_CAP_START + 10;
public const int WM_CAP_DRIVER_DISCONNECT = WM_CAP_START + 11;
public const int WM_CAP_DLG_VIDEODISPLAY = WM_CAP_START + 42;
public const int WM_CAP_GET_VIDEOFORMAT = WM_CAP_START + 44;
public const int WM_CAP_SET_VIDEOFORMAT = WM_CAP_START + 45;
public const int WM_CAP_SET_PREVIEW = WM_CAP_START + 50;
public const int WM_CAP_SET_PREVIEWRATE = WM_CAP_START + 52;
public const int WM_CAP_GRAB_FRAME = WM_CAP_START + 60;
public const int WM_CAP_GRAB_FRAME_NOSTOP = WM_CAP_START + 61;

[DllImport("user32", EntryPoint = "SendMessage")]
public static extern int SendBitmapMessage(IntPtr hWnd, uint wMsg, int wParam, ref BITMAPINFO lParam);



public void Attach(System.Windows.Forms.Control control)
{
deviceHandle = capCreateCaptureWindow("", Constants.WS_VISIBLE | Constants.WS_CHILD, 0, 0,control.Width,control.Height, control.Handle, 0);
bInfo=new SystemDLL.User32.BITMAPINFO();
bInfo.bmiHeader = new BITMAPINFOHEADER();
if (SendMessage(deviceHandle, Constants.WM_CAP_DRIVER_CONNECT, (IntPtr)deviceNumber, (IntPtr)0).ToInt32() > 0)
{
SendMessage(deviceHandle, Constants.WM_CAP_SET_SCALE, (IntPtr)(-1), (IntPtr)0);
SendMessage(deviceHandle, Constants.WM_CAP_SET_PREVIEWRATE, (IntPtr)0x42, (IntPtr)0);
SendMessage(deviceHandle,Constants.WM_CAP_SET_PREVIEW, (IntPtr)(-1), (IntPtr)0);
bInfo=new BITMAPINFO();
bInfo.bmiHeader = new BITMAPINFOHEADER();
SendBitmapMessage(deviceHandle, WM_CAP_GET_VIDEOFORMAT, Marshal.SizeOf(bInfo), ref bInfo);
bInfo.bmiHeader.biSize = (uint)Marshal.SizeOf(bInfo.bmiHeader);
bInfo.bmiHeader.biWidth = control.Width;
bInfo.bmiHeader.biHeight = control.Height;
SendBitmapMessage(deviceHandle, WM_CAP_SET_VIDEOFORMAT, Marshal.SizeOf(bInfo), ref bInfo);
    
SetWindowPos(deviceHandle, new IntPtr(1), 0, 0,control.Width ,control.Height, 6);
}
else
{
MessageBox.Show("Webcam not found ");
DestroyWindow(deviceHandle);
}
}

SendBitmapMessage(deviceHandle, WM_CAP_GET_VIDEOFORMAT, Marshal.SizeOf(bInfo), ref bInfo);

工作正常，但

is working fine but

SendBitmapMessage(deviceHandle, WM_CAP_SET_VIDEOFORMAT, Marshal.SizeOf(bInfo), ref bInfo);

不起作用。（为什么？）

does not work.(why?)

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