c# – 如何绘制矩形集合的轮廓？

作为我正在研究的项目的一部分,我必须从图像中存储和恢复魔杖区域.为了获得存储数据,我正在使用 GetRegionData方法.根据规范指定,此方法：

Returns a RegionData that represents the information that describes this Region.

我将RegionData.Data属性中保存的byte []存储在base64字符串中,所以我可以稍后通过一种非常规的方法检索RegionData：

// This "instantiates" a RegionData object by simply initiating an object and setting the object type pointer to the specified type.
// Constructors don't run,but in this very specific case - they don't have to. The RegionData's only member is a "data" byte array,which we set right after.
var regionData =
    (RegionData)FormatterServices.GetUninitializedObject(typeof(RegionData));
regionData.Data = bytes;

然后我创建一个Region并在构造函数中传递上面的RegionData对象,并调用GetRegionScans来获取构成该区域的矩形对象：

var region = new Region(regionData);
RectangleF[] rectangles = region.GetRegionScans(new Matrix());

这样我最终得到了一组用于绘制和重建区域的矩形.我已将整个绘图过程隔离到WinForms应用程序,并且我使用以下代码在图像控件上绘制此矩形集合：

using (var g = Graphics.FromImage(picBox.Image))
{
    var p = new Pen(Color.Black,1f);
    var alternatePen = new Pen(Color.BlueViolet,1f);
    var b = new SolidBrush(picBox.BackColor);
    var niceBrush = new SolidBrush(Color.Orange);

    foreach (var r in rectangles)
    {
        g.DrawRectangle(p,new Rectangle(new Point((int)r.Location.X,(int)r.Location.Y),new Size((int)r.Width,(int)r.Height)));
    }
}

上面的代码导致在我的图片控件中呈现以下内容：

这里的大纲是正确的 – 这正是我最初使用魔棒工具标记的内容.然而,当我绘制矩形时,我也最终得到了水平线,这些线不是原始魔棒选择的一部分.因此,我无法再查看实际图像,而我的魔棒工具现在使图像变得无用.

我想我只会在屏幕上绘制每个矩形的左右边缘,所以我最终会在屏幕上显示一堆点,为我勾勒出图像的轮廓.为此,我尝试了以下代码：

var pointPair = new[]
{
    new Point((int) r.Left,(int) r.Y),new Point((int) r.Right,(int) r.Y)
};

g.DrawRectangle(p,pointPair[0].X,pointPair[0].Y,1,1);
g.DrawRectangle(p,pointPair[1].X,pointPair[1].Y,1);

结果可以在下面观察到：

虽然距离较近,但它仍然没有雪茄.

我正在寻找一种连接点的方法,以便在我的区域中创建矩形的轮廓.对人类而言微不足道的事情,但我无法弄清楚如何指导计算机为我做这件事.

我已经尝试通过计算每个矩形的左和右点上的最邻近点,并将它们渲染为单独的矩形,从每个矩形创建新点,但无济于事.

任何帮助将不胜感激,因为我真的在这里不知所措.

谢谢！

解

感谢Peter Duniho的回答,我设法解决了这个问题.为了完整起见,我在下面包含了SafeHandle包装类和我用来完成这项工作的代码.

绘图代码

下面的代码是我用来绘制区域轮廓的代码.

private void DrawRegionOutline(Graphics graphics,Color color,Region region)
    {
        var regionHandle = new SafeRegionHandle(region,region.GetHrgn(graphics));
        var deviceContext = new SafeDeviceContextHandle(graphics);
        var brushHandle = new SafeBrushHandle(color);

        using (regionHandle)
        using (deviceContext)
        using (brushHandle)
            FrameRgn(deviceContext.DangerousGetHandle(),regionHandle.DangerousGetHandle(),brushHandle.DangerousGetHandle(),1);
    }

SafeHandleNative

SafeHandleZeroOrMinusOneIsInvalid周围的小包装,以确保在完成句柄后进行清理.

[HostProtection(MayLeakOnAbort = true)]
[SuppressUnmanagedCodeSecurity]
public abstract class SafeNativeHandle : SafeHandleZeroOrMinusOneIsInvalid
{
    #region Platform Invoke

    [DllImport("kernel32.dll",SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    protected internal static extern bool CloseHandle(IntPtr hObject);

    #endregion

    /// <summary>
    /// Initializes a new instance of the <see cref="SafeNativeHandle"/> class.
    /// </summary>
    protected SafeNativeHandle() : base(true)
    {}

    /// <summary>
    /// Initializes a new instance of the <see cref="SafeNativeHandle"/> class.
    /// </summary>
    /// <param name="handle">The handle.</param>
    protected SafeNativeHandle(IntPtr handle)
        : base(true)
    {
        SetHandle(handle);
    }
}

我创建了三个其他包装器,一个用于Region对象,一个用于Brush,另一个用于设备上下文句柄.这些都继承自SafeNativeHandle,但为了不垃圾邮件,我只提供我用于下面区域的那个.其他两个包装器实际上是相同的,但使用相应的Win32 API来清理自己的资源.

public class SafeRegionHandle : SafeNativeHandle
{
    private readonly Region _region;

    /// <summary>
    /// Initializes a new instance of the <see cref="SafeRegionHandle" /> class.
    /// </summary>
    /// <param name="region">The region.</param>
    /// <param name="handle">The handle.</param>
    public SafeRegionHandle(Region region,IntPtr handle)
    {
        _region = region;
        base.handle = handle;
    }

    /// <summary>
    /// When overridden in a derived class,executes the code required to free the handle.
    /// </summary>
    /// <returns>
    /// true if the handle is released successfully; otherwise,in the event of a catastrophic failure,false. In this case,it generates a releaseHandleFailed MDA Managed Debugging Assistant.
    /// </returns>
    [ReliabilityContract(Consistency.WillNotCorruptState,Cer.MayFail)]
    protected override bool ReleaseHandle()
    {
        try
        {
            _region.ReleaseHrgn(handle);
        }
        catch
        {
            return false;
        }

        return true;
    }
}

[DllImport("gdi32")]
static extern bool FrameRgn(System.IntPtr hDC,System.IntPtr hRgn,IntPtr hBrush,int nWidth,int nHeight);

[DllImport("gdi32")]
static extern IntPtr CreateSolidBrush(uint colorref);

[DllImport("gdi32.dll")]
static extern bool DeleteObject([In] IntPtr hObject);

[StructLayout(LayoutKind.Explicit)]
struct COLORREF
{
    [FieldOffset(0)]
    public uint colorref;
    [FieldOffset(0)]
    public byte red;
    [FieldOffset(1)]
    public byte green;
    [FieldOffset(2)]
    public byte blue;

    public COLORREF(Color color)
        : this()
    {
        red = color.R;
        green = color.G;
        blue = color.B;
    }
}

void DrawRegion(Graphics graphics,Region region)
{
    COLORREF colorref = new COLORREF(color);
    IntPtr hdc = IntPtr.Zero,hbrush = IntPtr.Zero,hrgn = IntPtr.Zero;

    try
    {
        hrgn = region.GetHrgn(graphics);
        hdc = graphics.GetHdc();
        hbrush = CreateSolidBrush(colorref.colorref);

        FrameRgn(hdc,hrgn,hbrush,1);
    }
    finally
    {
        if (hrgn != IntPtr.Zero)
        {
            region.ReleaseHrgn(hrgn);
        }

        if (hbrush != IntPtr.Zero)
        {
            DeleteObject(hbrush);
        }

        if (hdc != IntPtr.Zero)
        {
            graphics.ReleaseHdc(hdc);
        }
    }
}