C# 使用TextRenderer将文本绘制为位图

我正在尝试使用

TextRenderer

（因为这有利于使用

Graphics.DrawString

）将一些文本绘制到

位图

，但是这会产生一些非常不希望的效果

示例代码

using (Bitmap buffer = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb))
{
    using (Graphics graphics = Graphics.FromImage(buffer))
    {
        // Produces the result below
        graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;
        // Produces clean text, but I'd really like ClearType!
        graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAliasGridFit;
        TextRenderer.DrawText(graphics, "Hello World", this.Font, this.ClientRectangle, Color.Black);
    }
    e.Graphics.DrawImageUnscaled(buffer, this.ClientRectangle);
}

结果

我不知道怎么解决这个问题…救命

我不想使用

Graphics.DrawString

，因为我想要正确的GDI（与GDI+渲染相反）

注意：我刚刚意识到，我在这个问题上留下了一个很大的漏洞。一些人指出，在他们的机器上呈现ClearType文本工作得很好

---

我正在尝试将文本渲染为透明（Color.transparent）位图。如果我用纯色，一切都很好！（但我必须渲染为透明位图）。

在调用DrawText（）时指定背景色：

---

您可以尝试为

图像图形设置
textrendinghint
：

using (Graphics graphics = Graphics.FromImage(buffer))
{
    graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAliasGridFit;
    TextRenderer.DrawText(graphics, "Hello World", this.Font, this.ClientRectangle, Color.Black);
}

问题是TextRenderer使用GDI渲染来渲染文本，clear type使用特殊的抗锯齿算法来平滑文本，不幸的是，当您尝试在位图设备上绘制时，它不起作用

要使其工作，您必须使用技巧，在内存中绘制，然后复制到位图：

创建与显示设备上下文（IntPtr.Zero handle）兼容的内存位图缓冲区
用纯色或图像填充缓冲区背景
将文本渲染到内存位图中
从内存位图复制到图像设备上下文（BitBlt）
有关详细信息，请参阅此博客：

示例代码，抱歉有点长：

public static class Test
{
    public static Image Render()
    {
        // create the final image to render into
        var image = new Bitmap(190, 30, PixelFormat.Format32bppArgb);

        // create memory buffer from desktop handle that supports alpha channel
        IntPtr dib;
        var memoryHdc = CreateMemoryHdc(IntPtr.Zero, image.Width, image.Height, out dib);
        try
        {
            // create memory buffer graphics to use for HTML rendering
            using (var memoryGraphics = Graphics.FromHdc(memoryHdc))
            {
                // must not be transparent background 
                memoryGraphics.Clear(Color.White);

                // execute GDI text rendering
                TextRenderer.DrawText(memoryGraphics, "Test string 1", new Font("Arial", 12), new Point(5, 5), Color.Red, Color.Wheat);
                TextRenderer.DrawText(memoryGraphics, "Test string 2", new Font("Arial", 12), new Point(100, 5), Color.Red);
            }

            // copy from memory buffer to image
            using (var imageGraphics = Graphics.FromImage(image))
            {
                var imgHdc = imageGraphics.GetHdc();
                BitBlt(imgHdc, 0, 0, image.Width, image.Height, memoryHdc, 0, 0, 0x00CC0020);
                imageGraphics.ReleaseHdc(imgHdc);
            }
        }
        finally
        {
            // release memory buffer
            DeleteObject(dib);
            DeleteDC(memoryHdc);
        }

        return image;
    }

    private static IntPtr CreateMemoryHdc(IntPtr hdc, int width, int height, out IntPtr dib)
    {
        // Create a memory DC so we can work off-screen
        IntPtr memoryHdc = CreateCompatibleDC(hdc);
        SetBkMode(memoryHdc, 1);

        // Create a device-independent bitmap and select it into our DC
        var info = new BitMapInfo();
        info.biSize = Marshal.SizeOf(info);
        info.biWidth = width;
        info.biHeight = -height;
        info.biPlanes = 1;
        info.biBitCount = 32;
        info.biCompression = 0; // BI_RGB
        IntPtr ppvBits;
        dib = CreateDIBSection(hdc, ref info, 0, out ppvBits, IntPtr.Zero, 0);
        SelectObject(memoryHdc, dib);

        return memoryHdc;
    }

    [DllImport("gdi32.dll")]
    public static extern int SetBkMode(IntPtr hdc, int mode);

    [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
    private static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateDIBSection(IntPtr hdc, [In] ref BitMapInfo pbmi, uint iUsage, out IntPtr ppvBits, IntPtr hSection, uint dwOffset);

    [DllImport("gdi32.dll")]
    public static extern int SelectObject(IntPtr hdc, IntPtr hgdiObj);

    [DllImport("gdi32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, int dwRop);

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

    [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
    public static extern bool DeleteDC(IntPtr hdc);

    [StructLayout(LayoutKind.Sequential)]
    internal struct BitMapInfo
    {
        public int biSize;
        public int biWidth;
        public int biHeight;
        public short biPlanes;
        public short biBitCount;
        public int biCompression;
        public int biSizeImage;
        public int biXPelsPerMeter;
        public int biYPelsPerMeter;
        public int biClrUsed;
        public int biClrImportant;
        public byte bmiColors_rgbBlue;
        public byte bmiColors_rgbGreen;
        public byte bmiColors_rgbRed;
        public byte bmiColors_rgbReserved;
    }
}

尝试设置正确的
图形。插值模式
和
图形。平滑模式
@HamletHakobyan，我至少尝试过，但都没有解决问题。当使用Graphics.DrawString时，这些属性似乎可以工作，但是由于TextRenderer是GDI文本绘制系统，因此这些属性似乎不起作用。这样可以工作，但文本的背景实际上是图像，因此，文本的背景色应该是透明的。不幸的是，由于GDI不支持alpha，所以使用Color.Transparent无法正确混合ClearType文本。对抗锯齿文本有效，但对ClearType无效。我想要的是后者。@series0ne为什么需要
ClearType
？您所说的不适用于ClearType的
是什么意思？您应该更新代码以显示您的尝试。默认情况下（至少在我的系统上），TextRenderingHint是ClearType。因此，我的代码省略了TextRenderingHint，因为默认值已经是ClearType，因此没有必要显式定义TextRenderingHint。我认为这可能会解决问题…@series0ne只是您不想使用
TextRenderingHint
，我不知道为什么你的
图形。TextRenderingHint
有默认值
ClearType
，我测试了打印默认值，它是
SystemDefault
，
TextRenderingHint=TextRenderingHint。ClearTypeGridFit
也可以工作。嗨，我从BitBlt（）调用中得到一个异常。我试图将CallingConvention=CallingConvention.Cdecl添加到导入中，但没有任何区别。消息：调用PInvoke函数“BitmapRecognition！”！BitmapRecognition.Text:：BitBlt'已使堆栈不平衡。这可能是因为托管PInvoke签名与非托管目标签名不匹配。检查PInvoke签名的调用约定和参数是否与目标非托管签名匹配。哎呀，BitBlt的签名不正确，请将最后一个参数（dwRop）从long更改为int。抱歉。
public static class Test
{
    public static Image Render()
    {
        // create the final image to render into
        var image = new Bitmap(190, 30, PixelFormat.Format32bppArgb);

        // create memory buffer from desktop handle that supports alpha channel
        IntPtr dib;
        var memoryHdc = CreateMemoryHdc(IntPtr.Zero, image.Width, image.Height, out dib);
        try
        {
            // create memory buffer graphics to use for HTML rendering
            using (var memoryGraphics = Graphics.FromHdc(memoryHdc))
            {
                // must not be transparent background 
                memoryGraphics.Clear(Color.White);

                // execute GDI text rendering
                TextRenderer.DrawText(memoryGraphics, "Test string 1", new Font("Arial", 12), new Point(5, 5), Color.Red, Color.Wheat);
                TextRenderer.DrawText(memoryGraphics, "Test string 2", new Font("Arial", 12), new Point(100, 5), Color.Red);
            }

            // copy from memory buffer to image
            using (var imageGraphics = Graphics.FromImage(image))
            {
                var imgHdc = imageGraphics.GetHdc();
                BitBlt(imgHdc, 0, 0, image.Width, image.Height, memoryHdc, 0, 0, 0x00CC0020);
                imageGraphics.ReleaseHdc(imgHdc);
            }
        }
        finally
        {
            // release memory buffer
            DeleteObject(dib);
            DeleteDC(memoryHdc);
        }

        return image;
    }

    private static IntPtr CreateMemoryHdc(IntPtr hdc, int width, int height, out IntPtr dib)
    {
        // Create a memory DC so we can work off-screen
        IntPtr memoryHdc = CreateCompatibleDC(hdc);
        SetBkMode(memoryHdc, 1);

        // Create a device-independent bitmap and select it into our DC
        var info = new BitMapInfo();
        info.biSize = Marshal.SizeOf(info);
        info.biWidth = width;
        info.biHeight = -height;
        info.biPlanes = 1;
        info.biBitCount = 32;
        info.biCompression = 0; // BI_RGB
        IntPtr ppvBits;
        dib = CreateDIBSection(hdc, ref info, 0, out ppvBits, IntPtr.Zero, 0);
        SelectObject(memoryHdc, dib);

        return memoryHdc;
    }

    [DllImport("gdi32.dll")]
    public static extern int SetBkMode(IntPtr hdc, int mode);

    [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
    private static extern IntPtr CreateCompatibleDC(IntPtr hdc);

    [DllImport("gdi32.dll")]
    private static extern IntPtr CreateDIBSection(IntPtr hdc, [In] ref BitMapInfo pbmi, uint iUsage, out IntPtr ppvBits, IntPtr hSection, uint dwOffset);

    [DllImport("gdi32.dll")]
    public static extern int SelectObject(IntPtr hdc, IntPtr hgdiObj);

    [DllImport("gdi32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool BitBlt(IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, int dwRop);

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

    [DllImport("gdi32.dll", ExactSpelling = true, SetLastError = true)]
    public static extern bool DeleteDC(IntPtr hdc);

    [StructLayout(LayoutKind.Sequential)]
    internal struct BitMapInfo
    {
        public int biSize;
        public int biWidth;
        public int biHeight;
        public short biPlanes;
        public short biBitCount;
        public int biCompression;
        public int biSizeImage;
        public int biXPelsPerMeter;
        public int biYPelsPerMeter;
        public int biClrUsed;
        public int biClrImportant;
        public byte bmiColors_rgbBlue;
        public byte bmiColors_rgbGreen;
        public byte bmiColors_rgbRed;
        public byte bmiColors_rgbReserved;
    }
}