SVG File Size Reduction via Symbol-to-Glyph Conversion
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Solution Overview
Problem
Existing methods for converting PDF documents to SVG format often result in large file sizes due to reliance on line drawings, making them difficult to render efficiently, especially on devices with limited capabilities, and require text recognition which can be challenging, especially when text is represented using drawing information.
Innovation Solution
The method processes SVG files generated from PDF documents by identifying frequently occurring symbols below a certain size, converting them into glyphs of a font, and including these glyphs in the output SVG file, while retaining symbol definitions for less frequent or larger symbols, thereby reducing file size and improving renderability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PDF documents are converted to SVG format using line drawing commands, then the SVG file can be generated without text recognition, but the file size becomes large and rendering becomes difficult
Solution Approach 1:
The patent segments the SVG content into two distinct parts: (1) a font definition section containing glyph definitions for frequently occurring symbols, and (2) a content section that references these glyphs. This segmentation allows the system to store only unique glyph definitions once, rather than repeating line drawing commands for each symbol instance, thereby reducing file size while maintaining conversion reliability
Solution Approach 2:
Instead of copying line drawing commands for each symbol occurrence, the patent creates a single copy of each unique glyph definition in the font section, then references it multiple times in the content section. This approach reduces redundancy and file size while preserving the ability to accurately represent all symbols from the original PDF
2Quantity of substance
If text is recognized and converted using text fonts, then the SVG file size is reduced, but text recognition is required which is challenging when text is represented using drawing information
Solution Approach 1:
The patent introduces an intermediary representation system that bridges between line drawing symbols and text font glyphs. The system uses frequency analysis to identify which symbols should be converted to glyphs, and creates a mapping layer (the font definition section) that translates between the original symbol references and glyph representations, avoiding the need for direct text recognition while achieving compact file sizes
Solution Approach 2:
The patent changes the representation parameter of frequently occurring symbols from line drawing commands to glyph references. By analyzing symbol frequency and converting only the most common symbols to glyphs (rather than all symbols or none), the system optimizes file size reduction while minimizing the complexity of symbol-to-glyph mapping
3Quantity of substance
If all symbols are converted to glyphs, then the SVG file becomes more compact, but the number of glyphs may exceed browser support limits
Solution Approach 1:
The patent applies partial conversion by selecting only the most frequently occurring symbols for glyph conversion, rather than converting all symbols. The frequency analysis identifies a subset of symbols that, when converted to glyphs, provide the greatest file size reduction benefit. This partial action ensures the number of glyphs remains within browser support limits (typically 101 or lower) while still achieving significant compression
Data Source
AI summary
An input SVG file to be processed is accessed. Reusable symbols in the input SVG are identified, e.g., which satisfy a symbol size requirement. A set of symbols are selected from among the identified reusable symbols for conversion to glyphs of a custom binary font, e.g., based on symbol occurrence frequency. A binary font file is created corresponding to set the selected identified symbols in the SVG input file. An SVG output file is created including: binary font glyph definitions corresponding to the converted identified symbols, definitions of symbols from the SVG input file which have not been converted to glyphs and information indicating where the glyphs and symbols, which were not converted, are to be placed on an output display page. The generated SVG output file is a more efficient SVG file than the input SVG file. Different custom binary font files are created for different SVG input pages.