Render Presentations with Fallback Fonts in Python

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 to the FontsManager.font_fall_back_rules_collection property.

Once the fallback font rules collection is assigned to the presentation’s fonts_manager, 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 add_fall_back_fonts to another rule.
3. Set rules collection to FontsManager.font_fall_back_rules_collection property.
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.

import aspose.slides as slides

# Create new instance of a rules collection
rulesList = slides.FontFallBackRulesCollection()

# create a number of rules
rulesList.add(slides.FontFallBackRule(0x400, 0x4FF, "Times New Roman"))

for fallBackRule in rulesList:
	#Trying to remove FallBack font "Tahoma" from loaded rules
	fallBackRule.remove("Tahoma")

	#And to update of rules for specified range
	if fallBackRule.range_end_index >= 0x4000 and fallBackRule.range_start_index < 0x5000:
		fallBackRule.add_fall_back_fonts("Verdana")

#Also we can remove any existing rules from list
if len(rulesList) > 0:
	rulesList.remove(rulesList[0])

with slides.Presentation(path + "input.pptx") as pres:
	#Assigning a prepared rules list for using
	pres.fonts_manager.font_fall_back_rules_collection = rulesList

	# Rendering of thumbnail with using of initialized rules collection and saving to PNG
	with pres.slides[0].get_image(1, 1) as img:
		img.save("Slide_0.png", slides.ImageFormat.PNG)

Read more about how to Convert PowerPoint Slides to PNG in Python.