Text Rendering using TrueType Font | Java

Rendering Text

In order to render text, the Rendering subsystem requires the implementation of Aspose.Font.Rendering.IGlyphOutlinePainter interface to draw glyph. This can be achieved using the following steps.

  1. Create method DrawText() which draws specified text into System.Drawing.Bitmap object and saves resultant bitmap on Disc. This will include the following steps:

Auxillary steps for this strategy

Implementation of DrawText method is as shown below.

 1// For complete examples and data files, please go to https://github.com/aspose-font/Aspose.Font-for-Java
 2static void drawText(String text, IFont font, double fontSize,
 3           Paint backgroundBrush, Paint textBrush, String outFile) throws Exception
 4{
 5    //Get glyph identifiers for every symbol in text line
 6    GlyphId[] gids = new GlyphId[text.length()];
 7    for (int i = 0; i < text.length(); i++)
 8        gids[i] = font.getEncoding().decodeToGid(text.charAt(i));
 9    // set common drawing settings
10    double dpi = 300;
11	
12    double resolutionCorrection = dpi / 72; // 72 is font's internal dpi
13    // prepare output bitmap
14    BufferedImage outBitmap = new BufferedImage(960, 720, BufferedImage.TYPE_INT_BGR);
15    //outBitmap.getRaster().SetResolution((float)dpi, (float)dpi);
16    java.awt.Graphics2D outGraphics = (java.awt.Graphics2D) outBitmap.getGraphics();
17    outGraphics.setPaint(backgroundBrush);
18    outGraphics.fillRect(0, 0, outBitmap.getWidth(), outBitmap.getHeight());
19    outGraphics.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
20    //declare coordinate variables and previous gid
21    GlyphId previousGid = null;
22    double glyphXCoordinate = 0;
23    double glyphYCoordinate = fontSize * resolutionCorrection;
24    //loop which paints every glyph in gids
25    for (GlyphId gid : gids)
26    {
27        // if the font contains the gid
28        if (gid != null)
29        {
30            Glyph glyph = font.getGlyphAccessor().getGlyphById(gid);
31            if (glyph == null)
32                continue;
33	
34            // path that accepts drawing instructions
35            GeneralPath path = new GeneralPath();
36	
37            // Create IGlyphOutlinePainter implementation
38            GlyphOutlinePainter outlinePainter = new GlyphOutlinePainter(path);
39	
40            // Create the renderer
41            IGlyphRenderer renderer = new GlyphOutlineRenderer(outlinePainter);
42	
43            // get common glyph properties
44            double kerning = 0;
45	
46            // get kerning value
47            if (previousGid != null)
48            {
49                kerning = (font.getMetrics().getKerningValue(previousGid, gid) /
50                           glyph.getSourceResolution()) * fontSize * resolutionCorrection;
51                kerning += fontWidthToImageWdith(font.getMetrics().getGlyphWidth(previousGid),
52                        glyph.getSourceResolution(), fontSize, 300);
53            }
54	
55            // glyph positioning - increase glyph X coordinate according to kerning distance
56            glyphXCoordinate += kerning;
57	
58            // Glyph placement matrix
59            TransformationMatrix glyphMatrix =
60                new TransformationMatrix(
61                    new double[]
62                            {
63                                    fontSize*resolutionCorrection,
64                                    0,
65                                    0,
66                                // negative because of bitmap coordinate system begins from the top
67                                    - fontSize*resolutionCorrection,
68                                    glyphXCoordinate,
69                                    glyphYCoordinate
70                            });
71	
72            // render current glyph
73            renderer.renderGlyph(font, gid, glyphMatrix);
74            // fill the path
75            path.setWindingRule(GeneralPath.WIND_NON_ZERO);
76            outGraphics.setPaint(textBrush);
77            outGraphics.fill(path);
78        }
79        //set current gid as previous to get correct kerning for next glyph
80        previousGid = gid;
81    }
82    //Save results
83    ImageIO.write(outBitmap, "jpg", new File(outFile));
84}

  1. create utility method to calculate font width to image width as shown in the code sample below
1// For complete examples and data files, please go to https://github.com/aspose-font/Aspose.Font-for-Java
2static double fontWidthToImageWidth(double width, int fontSourceResulution, double fontSize, double dpi)
3{
4    double resolutionCorrection = dpi / 72; // 72 is font's internal dpi
5    return (width / fontSourceResulution) * fontSize * resolutionCorrection;
6}

Calling the Rendering Text functionality

To use the above implementations, the following sample code can be executed from the Main method of a console based application.

 1// For complete examples and data files, please go to https://github.com/aspose-font/Aspose.Font-for-Java
 2String fileName1 = Utils.getDataDir() + "Montserrat-Bold.ttf"; //Font file name with full path
 3      FontDefinition fd1 = new FontDefinition(FontType.TTF, new FontFileDefinition("ttf", new FileSystemStreamSource(fileName1)));
 4      TtfFont font1 = (TtfFont) Font.open(fd1);
 5      
 6      String fileName2 = Utils.getDataDir() + "Lora-Bold.ttf"; //Font file name with full path
 7      FontDefinition fd2 = new FontDefinition(FontType.TTF, new FontFileDefinition("ttf", new FileSystemStreamSource(fileName2)));
 8      TtfFont font2 = (TtfFont) Font.open(fd2);
 9      
10      try {
11       drawText("Hello world", font1, 14, java.awt.Color.WHITE, java.awt.Color.BLACK, Utils.getDataDir() + "hello1_montserrat_out.jpg");
12       drawText("Hello world", font2, 14, java.awt.Color.YELLOW, java.awt.Color.RED, Utils.getDataDir() + "hello2_lora_out.jpg");
13      } catch (Exception ex) {
14      	ex.printStackTrace();
15      }
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