C# 图像处理(一)（图像缩放、屏幕截取、图像合并、保存图像）

Image screen = getScreen();                       // 截取屏幕  
saveImage(screen, screen.Size, @"d:\截屏.jpg");   // 保存截屏 

# region 图像处理功能函数

/// <summary>
/// 按指定尺寸对图像pic进行非拉伸缩放
/// </summary>
public static Bitmap shrinkTo(Image pic, Size S, Boolean cutting)
{
    //创建图像
    Bitmap tmp = new Bitmap(S.Width, S.Height);     //按指定大小创建位图

    //绘制
    Graphics g = Graphics.FromImage(tmp);           //从位图创建Graphics对象
    g.Clear(Color.FromArgb(0, 0, 0, 0));            //清空

    Boolean mode = (float)pic.Width / S.Width > (float)pic.Height / S.Height;   //zoom缩放
    if (cutting) mode = !mode;                      //裁切缩放

    //计算Zoom绘制区域             
    if (mode)
        S.Height = (int)((float)pic.Height * S.Width / pic.Width);
    else
        S.Width = (int)((float)pic.Width * S.Height / pic.Height);
    Point P = new Point((tmp.Width - S.Width) / 2, (tmp.Height - S.Height) / 2);

    g.DrawImage(pic, new Rectangle(P, S));

    return tmp;     //返回构建的新图像
}


//保存图像pic到文件fileName中，指定图像保存格式
public static void SaveToFile(Image pic, string fileName, bool replace, ImageFormat format)    //ImageFormat.Jpeg
{
    //若图像已存在，则删除
    if (System.IO.File.Exists(fileName) && replace)
        System.IO.File.Delete(fileName);

    //若不存在则创建
    if (!System.IO.File.Exists(fileName))
    {
        if (format == null) format = getFormat(fileName);   //根据拓展名获取图像的对应存储类型

        if (format == ImageFormat.MemoryBmp) pic.Save(fileName);
        else pic.Save(fileName, format);                    //按给定格式保存图像
    }
}

//根据文件拓展名，获取对应的存储类型
public static ImageFormat getFormat(string filePath)
{
    ImageFormat format = ImageFormat.MemoryBmp;
    String Ext = System.IO.Path.GetExtension(filePath).ToLower();

    if (Ext.Equals(".png")) format = ImageFormat.Png;
    else if (Ext.Equals(".jpg") || Ext.Equals(".jpeg")) format = ImageFormat.Jpeg;
    else if (Ext.Equals(".bmp")) format = ImageFormat.Bmp;
    else if (Ext.Equals(".gif")) format = ImageFormat.Gif;
    else if (Ext.Equals(".ico")) format = ImageFormat.Icon;
    else if (Ext.Equals(".emf")) format = ImageFormat.Emf;
    else if (Ext.Equals(".exif")) format = ImageFormat.Exif;
    else if (Ext.Equals(".tiff")) format = ImageFormat.Tiff;
    else if (Ext.Equals(".wmf")) format = ImageFormat.Wmf;
    else if (Ext.Equals(".memorybmp")) format = ImageFormat.MemoryBmp;

    return format;
}

[DllImport("user32.dll")]
static extern bool GetCursorInfo(out CURSORINFO pci);

private const Int32 CURSOR_SHOWING = 0x00000001;
[StructLayout(LayoutKind.Sequential)]
struct POINT
{
    public Int32 x;
    public Int32 y;
}

[StructLayout(LayoutKind.Sequential)]
struct CURSORINFO
{
    public Int32 cbSize;
    public Int32 flags;
    public IntPtr hCursor;
    public POINT ptScreenPos;
}

/// <summary>
/// 截取屏幕指定区域为Image，保存到路径savePath下，haveCursor是否包含鼠标
/// </summary>
public static Image getScreen(int x = 0, int y = 0, int width = -1, int height = -1, String savePath = "", bool haveCursor = true)
{
    if (width == -1) width = SystemInformation.VirtualScreen.Width;
    if (height == -1) height = SystemInformation.VirtualScreen.Height;

    Bitmap tmp = new Bitmap(width, height);                 //按指定大小创建位图
    Graphics g = Graphics.FromImage(tmp);                   //从位图创建Graphics对象
    g.CopyFromScreen(x, y, 0, 0, new Size(width, height));  //绘制

    // 绘制鼠标
    if (haveCursor)
    {
        try
        {
            CURSORINFO pci;
            pci.cbSize = Marshal.SizeOf(typeof(CURSORINFO));
            GetCursorInfo(out pci);
            System.Windows.Forms.Cursor cur = new System.Windows.Forms.Cursor(pci.hCursor);
            cur.Draw(g, new Rectangle(pci.ptScreenPos.x, pci.ptScreenPos.y, cur.Size.Width, cur.Size.Height));
        }
        catch (Exception ex) { }    // 若获取鼠标异常则不显示
    }

    //Size halfSize = new Size((int)(tmp.Size.Width * 0.8), (int)(tmp.Size.Height * 0.8));  // 按一半尺寸存储图像
    if (!savePath.Equals("")) saveImage(tmp, tmp.Size, savePath);       // 保存到指定的路径下

    return tmp;     //返回构建的新图像
}

/// <summary>
/// 缩放icon为指定的尺寸，并保存到路径PathName
/// </summary>
public static void saveImage(Image image, Size size, String PathName)
{
    Image tmp = shrinkTo(image, size, false);
    SaveToFile(tmp, PathName, true, null);
}

# endregion