在 .NET 中绘制完全对齐的字符串

Question

我需要将一个字符串拉到一个完全对齐的位图上。我知道 StringFormat.Alignment 不支持完全对齐的对齐。所以，我正在寻找一种解决方案来在完全对齐的位图上绘制字符串。 RictTextBox 有充分的理由，但我认为它使用 WinAPI 来证明文本。也许我可以用 RichTextBox 绘制文本，但我不知道如何在不显示在表单中的情况下获取控件位图（屏幕截图）。 System.Drawing.Graphics 是否有任何技巧或替代第三方库？

Answer 1

我使用了一种方法在位图上绘制RichTextBox。

public class ExtendedRichTextBox : RichTextBox
{
    private const double inch = 1440 / 96;//Not 14.4!!, believe me you can see someone use 1.44 but it doesn't work on big bitmaps. They round the 1440/96 as 14.4 but it works on only small sized works. use /96

    public void DrawToBitmap(Graphics graphics, Rectangle bound)
    {
        Update();  // Ensure RTB fully painted
        IntPtr hDC = graphics.GetHdc();
        FORMATRANGE fmtRange;

        RECT rect;
        rect.Left = (int)Math.Ceiling(bound.X * inch);
        rect.Top = (int)Math.Ceiling(bound.Y * inch);
        rect.Right = (int)Math.Ceiling(bound.Right * inch);
        rect.Bottom = (int)Math.Ceiling(bound.Bottom * inch);
        int fromAPI;

        fmtRange.hdc = hDC;
        fmtRange.hdcTarget = hDC;

        fmtRange.chrg.cpMin = 0;
        fmtRange.chrg.cpMax = -1;
        fmtRange.rc = rect;
        fmtRange.rcPage = rect;

        IntPtr lParam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));
        Marshal.StructureToPtr(fmtRange, lParam, false);
        fromAPI = SendMessage(Handle, EM_FORMATRANGE, 0, lParam);
        fromAPI = SendMessage(Handle, EM_FORMATRANGE, 1, lParam);
        Marshal.FreeCoTaskMem(lParam);
        fromAPI = SendMessage(Handle, EM_FORMATRANGE, 0, new IntPtr(0));
        graphics.ReleaseHdc(hDC);
    }
}

您可以在 pinvoke 网站上找到 WinApi 实现。但你也可以在这里：

[DllImport("USER32.dll")]
private static extern Int32 SendMessage(IntPtr hWnd, int msg, int wParam, IntPtr lParam);
private const int WM_USER = 0x400;
private const int EM_FORMATRANGE = WM_USER + 57;
[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
    public int Left;
    public int Top;
    public int Right;
    public int Bottom;
}

[StructLayout(LayoutKind.Sequential)]
private struct CHARRANGE
{
    public int cpMin;
    public int cpMax;
}

[StructLayout(LayoutKind.Sequential)]
private struct FORMATRANGE
{
    public IntPtr hdc;
    public IntPtr hdcTarget;
    public RECT rc;
    public RECT rcPage;
    public CHARRANGE chrg;
}

这里是使用的例子。

var richtext = new ExtendedRichTextBox(); 
/*I've implemented a RichTextBox but it isn't realted with this question. 
You can use simply RichTextBox. ExtendedRichTextBox has support rtl.*/

richtext.Font = font;
richtext.ForeColor = textColor;
richtext.Text = sometext;
richtext.SelectAll();
richtext.RightToLeft = rtl;
richtext.SelectionAlignment = align;

//Fix the rtl bug in RichTextBox
if (rtl == RightToLeft.Yes)
{
    if (align == TextAlign.Center)
        richtext.Rtf = richtext.Rtf.Replace(@"\qr", @"\qc");
    else if (align == TextAlign.Left)
        richtext.Rtf = richtext.Rtf.Replace(@"\qr", @"\ql");
    else if (align == TextAlign.Justify)
        richtext.Rtf = richtext.Rtf.Replace(@"\qr", @"\qj");
}

//textRect is where we want to put text in.
var tempBitmap = new Bitmap(textRect.Width, textRect.Height);
richtext.DrawToBitmap(Graphics.FromImage(tempBitmap), tempRect);
tempBitmap.MakeTransparent(richtext.BackColor);
graph.DrawImage(tempBitmap, panelRect.X, panelRect.Y);