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;
mWidth = width;
mHeight = height;
mLeft = left;

mTop = top;
}
/// <summary>
/// 打开视频
/// </summary>
public void StartVideo()
{
if (bWorkStart)
return;
bWorkStart = true;
byte[] lpszName = new byte[100];
//创建播放窗口
hWndC = capCreateCaptureWindowA(lpszName, WS_CHILD | WS_VISIBLE, mLeft, mTop, mWidth, mHeight, mControlPtr, 0);

if (hWndC.ToInt32() != 0)
{
//显示视频
SendMessage(hWndC, WM_CAP_SET_CALLBACK_VIDEOSTREAM, 0, 0);
SendMessage(hWndC, WM_CAP_SET_CALLBACK_ERROR, 0, 0);
SendMessage(hWndC, WM_CAP_SET_CALLBACK_STATUSA, 0, 0);
SendMessage(hWndC, WM_CAP_DRIVER_CONNECT, 0, 0);
SendMessage(hWndC, WM_CAP_SET_SCALE, 1, 0);
SendMessage(hWndC, WM_CAP_SET_PREVIEWRATE, 100, 0);
SendMessage(hWndC, WM_CAP_SET_OVERLAY, 1, 0);
SendMessage(hWndC, WM_CAP_SET_PREVIEW, 1, 0);
}
}
/// <summary>
/// 关闭视频
/// </summary>
public void StopVideo()
{
SendMessage(hWndC, WM_CAP_DRIVER_DISCONNECT, 0, 0);
bWorkStart = false;
}

/// <summary>
/// 拍照
/// </summary>
/// <param name="path">文件路径</param>
public void Images(string path)
{
IntPtr imagePath = Marshal.StringToHGlobalAnsi(path);
SendMessage(hWndC, WM_CAP_SAVEDIB, 0, imagePath.ToInt32());
}

}
}
拍照完成后就是不知道怎么改变照片的分辨率。。望给予指点。。。

[解决办法]
是要缩小图片吗？
按照比例缩小就行了。
刚从另外一个帖子看到的。
using System;
using System.Collections.Generic;
using System.Text;
using System.Drawing;

namespace Common
{
public class ImageMes
{
/// <summary>
/// 生成缩略图
/// </summary>
/// <param name="originalImagePath">源图路径</param>
/// <param name="thumbnailPath">缩略图路径</param>
/// <param name="width">缩略图宽度</param>
/// <param name="height">缩略图高度</param>
/// <param name="mode">生成缩略图的方式:HW指定高宽缩放(可能变形);W指定宽，高按比例 H指定高，宽按比例 Cut指定高宽裁减(不变形)</param>　　
/// <param name="mode">要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为jpg</param>　　
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType)
{
Image originalImage = Image.FromFile(originalImagePath);
int towidth = width;
int toheight = height;
int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;

switch (mode)
{
case "HW"://指定高宽缩放（可能变形）　　　　　　　　
break;
case "W"://指定宽，高按比例　　　　　　　　　　
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H"://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;

break;
case "Cut"://指定高宽裁减（不变形）　　　　　　　　
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
default:
break;
}
//新建一个bmp图片
Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

//新建一个画板
Graphics g = System.Drawing.Graphics.FromImage(bitmap);

//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

//设置高质量,低速度呈现平滑程度
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

//清空画布并以透明背景色填充
g.Clear(Color.Transparent);

//在指定位置并且按指定大小绘制原图片的指定部分
g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
new Rectangle(x, y, ow, oh),
GraphicsUnit.Pixel);

try
{
//以jpg格式保存缩略图
switch (imageType.ToLower())
{
case "gif":
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);
break;
case "jpg":
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
break;
case "bmp":
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);
break;
case "png":
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);
break;
default:
bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
break;
}
}
catch (System.Exception e)
{
throw e;
}
finally
{
originalImage.Dispose();
bitmap.Dispose();
g.Dispose();
}
}
}
}