6

我正在尝试使用TextRenderer（因为这有利于使用Graphics.DrawString）绘制一些文本到 a Bitmap，但是它有一些非常不受欢迎的效果。

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

在此处输入图像描述

我不确定如何解决这个问题...帮助！

我不想使用Graphics.DrawString，因为我想要正确的 GDI（而不是 GDI+）渲染。

注意：我刚刚意识到，我在这个问题上留下了一个巨大的漏洞。有些人指出，渲染 ClearType 文本在他们的机器上运行良好......

我正在尝试将文本呈现为透明（Color.Transparent）位图。如果我用纯色做，一切正常！（但我必须渲染到透明位图）。

4

3 回答 3

4

您可以尝试设置TextRenderingHint您的Image Graphics：

using (Graphics graphics = Graphics.FromImage(buffer))
{
    graphics.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAliasGridFit;
    TextRenderer.DrawText(graphics, "Hello World", this.Font, this.ClientRectangle, Color.Black);
}
于 2013-09-17T02:36:29.213 回答
4

在对 DrawText() 的调用中指定 BackColor：

TextRenderer.DrawText(graphics, "Hello World", this.Font, this.ClientRectangle, Color.Black, this.BackColor);
于 2013-09-16T23:28:10.187 回答
4

问题是TextRenderer使用GDI渲染，使用ClearType渲染文本，clear-type使用特殊的抗锯齿算法来平滑文本，不幸的是当你尝试在位图设备上绘制时它不起作用。

为了让它工作，你必须使用一个技巧，在内存中绘制，然后复制到位图：

  1. 创建与显示设备上下文兼容的内存位图缓冲区（IntPtr.Zero 句柄）
  2. 用纯色或图像填充缓冲区背景
  3. 将文本渲染到内存位图中
  4. 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：GDI text rendering to image。

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;
    }
}
于 2014-05-29T11:52:45.463 回答