Render Presentations with Fallback Fonts in JavaScript

Overview

Aspose.Slides allows you to render presentations using fallback font rules. This article shows how to create a fallback font rules collection, modify its rules by removing or adding fallback fonts, and assign the collection using the FontsManager.setFontFallBackRulesCollection method.

Once the fallback font rules collection is assigned to the presentation’s FontsManager, the rules are applied during operations such as saving, rendering, and converting the presentation. The example demonstrates how to use the configured rules when rendering a slide thumbnail and saving it as a PNG image.

Render a Slide Using Fallback Font Rules

The following example includes these steps:

1. We create fallback font rules collection.
2. Remove a fallback font rule and addFallBackFonts to another rule.
3. Set rules collection to getFontsManager.getFontFallBackRulesCollection method.
4. With Presentation.save method we can save presentation in the same format, or save it in another one. After fallback font rules collection is set to FontsManager, these rules are applied during any operations over the presentation: save, render, convert, etc.

// Create new instance of a rules collection
var rulesList = new aspose.slides.FontFallBackRulesCollection();
// create a number of rules
rulesList.add(new aspose.slides.FontFallBackRule(0x400, 0x4ff, "Times New Roman"));
for (let i = 0; i < rulesList.size(); i++) {
    let fallBackRule = rulesList.get_Item(0);
    // Trying to remove FallBack font "Tahoma" from loaded rules
    fallBackRule.remove("Tahoma");
    // And to update of rules for specified range
    if ((fallBackRule.getRangeEndIndex() >= 0x4000) && (fallBackRule.getRangeStartIndex() < 0x5000)) {
        fallBackRule.addFallBackFonts("Verdana");
    }
}
// Also we can remove any existing rules from list
if (rulesList.size() > 0) {
    rulesList.remove(rulesList.get_Item(0));
}
var pres = new aspose.slides.Presentation("input.pptx");
try {
    // Assigning a prepared rules list for using
    pres.getFontsManager().setFontFallBackRulesCollection(rulesList);
    // Rendering of thumbnail with using of initialized rules collection and saving to JPEG
    var slideImage = pres.getSlides().get_Item(0).getImage(1.0, 1.0);
    // Save the image to disk in JPEG format
    try {
        slideImage.save("Slide_0.jpg", aspose.slides.ImageFormat.Jpeg);
    } finally {
        if (slideImage != null) {
            slideImage.dispose();
        }
    }
} finally {
    if (pres != null) {
        pres.dispose();
    }
}

Read more about how to Convert PPT and PPTX to JPG in JavaScript.