使用Type1字体|的文本渲染| Aspose.Font for .NET

渲染文字

要使用字形轮廓渲染器呈现文本，请实现 Aspose.Font.Rendering.IGlyphOutlinePainter 接口，并使用它为各个字形构建路径。

1. 创建一个接受 System.Drawing.Drawing2D.GraphicsPath 的 Type1GlyphOutlinePainter 类。该类的方法将字体轮廓命令转换为路径中的直线和贝塞尔曲线。

// Implement a painter that builds a graphics path from a glyph outline

internal sealed class Type1GlyphOutlinePainter : IGlyphOutlinePainter
{
    private readonly GraphicsPath path;
    private PointF currentPoint;

    public Type1GlyphOutlinePainter(GraphicsPath path)
    {
        this.path = path;
    }

    public void MoveTo(MoveTo moveTo)
    {
        path.CloseFigure();
        currentPoint = new PointF((float)moveTo.X, (float)moveTo.Y);
    }

    public void LineTo(LineTo lineTo)
    {
        PointF nextPoint = new PointF((float)lineTo.X, (float)lineTo.Y);
        path.AddLine(currentPoint, nextPoint);
        currentPoint = nextPoint;
    }

    public void CurveTo(CurveTo curveTo)
    {
        PointF nextPoint = new PointF((float)curveTo.X3, (float)curveTo.Y3);
        path.AddBezier(
            currentPoint,
            new PointF((float)curveTo.X1, (float)curveTo.Y1),
            new PointF((float)curveTo.X2, (float)curveTo.Y2),
            nextPoint);
        currentPoint = nextPoint;
    }

    public void ClosePath()
    {
        path.CloseFigure();
    }
}

2. 创建 DrawText() 方法，将文本绘制到 System.Drawing.Bitmap 并保存为 PNG 文件。该方法执行以下操作：

• 将文本中的每个字符解码为字形 ID。
• 创建一个 300 DPI、960 × 720 的位图，填充背景并启用高质量平滑处理。
• 对于每个字形，将前一个字形的前进宽度和字偶距值添加到其水平位置。
• 为当前字形创建 GraphicsPath、Type1GlyphOutlinePainter 和 GlyphOutlineRenderer。
• 使用 TransformationMatrix 缩放和定位字形，然后使用指定的文本画笔填充路径。
• 将位图明确保存为 PNG。位图、图形对象和字形路径在使用后释放。

本例中的基线保持不变。水平坐标由前一个字形的前进宽度和字偶距累加得到。FontWidthToImageWidth() 使用源分辨率、字体大小和 DPI 将字体单位转换为图像像素。

DrawText() 的实现如下所示。

// Render text into a bitmap with a custom glyph outline painter

private static void DrawText(string text, IFont font, double fontSize,
    Brush backgroundBrush, Brush textBrush, string outputFile)
{
    GlyphId[] glyphIds = text
        .Select(character => font.Encoding.DecodeToGid(character))
        .ToArray();
    const double dpi = 300;
    double resolutionCorrection = dpi / 72;

    using var outputBitmap = new Bitmap(960, 720);
    outputBitmap.SetResolution((float)dpi, (float)dpi);
    using Graphics outputGraphics = Graphics.FromImage(outputBitmap);
    outputGraphics.FillRectangle(backgroundBrush, 0, 0, outputBitmap.Width, outputBitmap.Height);
    outputGraphics.SmoothingMode = SmoothingMode.HighQuality;

    GlyphId? previousGlyphId = null;
    double glyphXCoordinate = 0;
    double glyphYCoordinate = fontSize * resolutionCorrection;

    foreach (GlyphId glyphId in glyphIds)
    {
        Glyph glyph = font.GlyphAccessor.GetGlyphById(glyphId);
        if (glyph == null)
            continue;

        if (previousGlyphId != null)
        {
            double kerning = font.Metrics.GetKerningValue(previousGlyphId, glyphId)
                / (double)glyph.SourceResolution * fontSize * resolutionCorrection;
            double advance = FontWidthToImageWidth(
                font.Metrics.GetGlyphWidth(previousGlyphId),
                glyph.SourceResolution,
                fontSize,
                dpi);
            glyphXCoordinate += kerning + advance;
        }

        using var path = new GraphicsPath();
        var outlinePainter = new Type1GlyphOutlinePainter(path);
        IGlyphRenderer renderer = new GlyphOutlineRenderer(outlinePainter);
        var glyphMatrix = new TransformationMatrix(new double[]
        {
            fontSize * resolutionCorrection,
            0,
            0,
            -fontSize * resolutionCorrection,
            glyphXCoordinate,
            glyphYCoordinate
        });

        renderer.RenderGlyph(font, glyphId, glyphMatrix);
        path.FillMode = FillMode.Winding;
        outputGraphics.FillPath(textBrush, path);
        previousGlyphId = glyphId;
    }

    outputBitmap.Save(outputFile, ImageFormat.Png);
}

3. 添加将字体单位宽度转换为图像像素的实用方法。

// Convert a width in font units to pixels

private static double FontWidthToImageWidth(double width, int fontSourceResolution,
    double fontSize, double dpi = 300)
{
    double resolutionCorrection = dpi / 72;
    return width / fontSourceResolution * fontSize * resolutionCorrection;
}

调用文本渲染功能

以下示例从 DataDir 加载 Type1/courier.pfb，使用两种配色渲染相同的文本，并将两个 PNG 文件写入 OutputDir。

// Load a Type1 font and render text in two color schemes

string fileName = Path.Combine(DataDir, "Type1", "courier.pfb");
FontDefinition fontDefinition = new FontDefinition(
    FontType.Type1,
    new FontFileDefinition("pfb", new FileSystemStreamSource(fileName)));

Type1Font? font = Aspose.Font.Font.Open(fontDefinition) as Type1Font;
if (font == null)
    throw new InvalidOperationException("Unable to load the Type1 font.");

string firstOutput = Path.Combine(OutputDir, "hello1_type1_out.png");
string secondOutput = Path.Combine(OutputDir, "hello2_type1_out.png");
DrawText("Hello world", font, 14, Brushes.White, Brushes.Black, firstOutput);
DrawText("Hello world", font, 14, Brushes.Yellow, Brushes.Red, secondOutput);