Embed Fonts in a Presentation
Embed a permitted font in full or with used characters, then reopen and render without its external folder.
Input and prerequisites
Use .NET SDK 8.0.427 and Aspose.Slides for .NET 26.10.0 with the supplied pinned project. Set ASPOSE_LICENSE_PATH to your own valid license file; no license file is distributed. This complete fixture stops clearly when no license has been applied.
The code downloads pinned Noto fonts from their official repositories and verifies SHA-256 before loading them from an application folder. Internet access is required on the first run; the fonts are not installed system-wide or included in this project ZIP. See the Noto font license and Noto CJK license. Both are SIL Open Font License 1.1. Preserve their notices if you redistribute the fonts.
Download the complete project, including code, project and package lock. It was executed on Windows.
Example
The program downloads and verifies the regular Noto Sans font. It writes separate full and used-character embedded copies, lists their embedded font family after reopening, clears the font cache, removes the downloaded file, and renders the full-font copy. The fixture does not rely on a system installation of Noto Sans.
using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Net.Http;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Text.Json;
using System.Text.RegularExpressions;
using Aspose.Slides;
using Aspose.Slides.Export;
using Aspose.Slides.Warnings;
internal static class Program
{
private static void Main()
{
ApplyLicense();
PrepareFonts(false);
try
{
byte[] font = File.ReadAllBytes("fonts/NotoSans-Regular.ttf");
foreach (bool full in new[] { true, false })
{
using var p = new Presentation();
p.SlideSize.SetSize(640, 360, SlideSizeScaleType.DoNotScale);
var shape = Label(p.Slides[0], "Embedded Noto Sans");
shape.TextFrame.Paragraphs[0].Portions[0].PortionFormat.LatinFont = new FontData("Noto Sans");
p.FontsManager.AddEmbeddedFont(font, full ? EmbedFontCharacters.All : EmbedFontCharacters.OnlyUsed);
p.Save(full ? "full.pptx" : "used.pptx", SaveFormat.Pptx);
}
FontsLoader.ClearCache();
File.Delete("fonts/NotoSans-Regular.ttf");
foreach (string file in new[] { "full.pptx", "used.pptx" })
{
using var p = new Presentation(file);
Require(p.FontsManager.GetEmbeddedFonts().Any(f => f.FontName == "Noto Sans"), "Embedded family missing in " + file);
Require(p.Slides[0].Shapes.OfType<IAutoShape>().Single().TextFrame.Text == "Embedded Noto Sans", "Text changed.");
if (file == "full.pptx") Render(p.Slides[0], "preview.png");
}
Require(!File.Exists("fonts/NotoSans-Regular.ttf"), "External font file still exists.");
Report(new { full_embedded = true, used_embedded = true, reopened_without_external_file = true, text_retained = true });
}
finally { FontsLoader.ClearCache(); }
}
private static void PrepareFonts(bool includeOtherScripts)
{
Directory.CreateDirectory("fonts");
using var client = new HttpClient { Timeout = TimeSpan.FromMinutes(2) };
var fonts = new (string Name, string Url, string Hash)[]
{
("NotoSans-Regular.ttf", "https://raw.githubusercontent.com/notofonts/noto-fonts/ffebf8c1ee449e544955a7e813c54f9b73848eac/hinted/ttf/NotoSans/NotoSans-Regular.ttf", "b85c38ecea8a7cfb39c24e395a4007474fa5a4fc864f6ee33309eb4948d232d5"),
("NotoNaskhArabic-Regular.ttf", "https://raw.githubusercontent.com/notofonts/noto-fonts/ffebf8c1ee449e544955a7e813c54f9b73848eac/hinted/ttf/NotoNaskhArabic/NotoNaskhArabic-Regular.ttf", "2f4b88e6ee50fa82c617e2d1d4ba18281cb1c6cd71c3af3ec64970c23995db4b"),
("NotoSansCJKsc-Regular.otf", "https://raw.githubusercontent.com/notofonts/noto-cjk/f8d157532fbfaeda587e826d4cd5b21a49186f7c/Sans/OTF/SimplifiedChinese/NotoSansCJKsc-Regular.otf", "2c76254f6fc379fddfce0a7e84fb5385bb135d3e399294f6eeb6680d0365b74b"),
};
foreach (var font in includeOtherScripts ? fonts : fonts.Take(1))
{
string path = Path.Combine("fonts", font.Name);
if (!File.Exists(path) || Hash(path) != font.Hash)
{
byte[] bytes = client.GetByteArrayAsync(font.Url).GetAwaiter().GetResult();
Require(Convert.ToHexString(SHA256.HashData(bytes)).ToLowerInvariant() == font.Hash, "Downloaded font hash differs: " + font.Name);
File.WriteAllBytes(path, bytes);
}
}
FontsLoader.ClearCache();
FontsLoader.LoadExternalFonts(new[] { Path.GetFullPath("fonts") });
}
private static void ApplyLicense()
{
var license = new Aspose.Slides.License();
string? path = Environment.GetEnvironmentVariable("ASPOSE_LICENSE_PATH");
if (!string.IsNullOrWhiteSpace(path)) license.SetLicense(path);
if (!license.IsLicensed()) throw new InvalidOperationException("Set ASPOSE_LICENSE_PATH to a valid license file.");
}
private static void Require(bool condition, string message)
{
if (!condition) throw new InvalidOperationException(message);
}
private static IAutoShape Label(IBaseSlide slide, string text, float y = 50)
{
var shape = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 40, y, 560, 90);
shape.TextFrame.Text = text;
shape.TextFrame.Paragraphs[0].Portions[0].PortionFormat.FontHeight = 24;
return shape;
}
private static string Hash(string path) => Convert.ToHexString(SHA256.HashData(File.ReadAllBytes(path))).ToLowerInvariant();
private static void Report(object checks)
{
string json = JsonSerializer.Serialize(new { checks }, new JsonSerializerOptions { WriteIndented = true });
File.WriteAllText("result.json", json);
Console.WriteLine(json);
}
private static void Render(ISlide slide, string output)
{
using var image = slide.GetImage(new Size(640, 360));
image.Save(output, Aspose.Slides.ImageFormat.Png);
}
}
Run and inspect the result
Extract the download into an empty directory and run:
dotnet restore Example.csproj --locked-mode
dotnet run --project Example.csproj --configuration Release --no-restore
The code writes “full.pptx”, “used.pptx”, “preview.png”, plus “result.json”. Checks stop execution on an unexpected result; inspect visual outputs as well as the recorded data.
Practical limits
Font availability and legal embedding permission are different checks. Preserve the font license and respect embedding restrictions for every font you use. Used-character embedding can require replacement fonts when later edits introduce new characters. PowerPoint and other readers may handle embedded fonts differently; inspect the intended reader.
Read the detailed guide for the full API and platform requirements.