class HexaPDF::Content::Processor

This class is used for processing content operators extracted from a content stream.

General Information¶ ↑

When a content stream is read, operators and their operands are extracted. After extracting these operators are usually processed with a Processor instance that ensures that the needed setup (like modifying the graphics state) is done before further processing.

How Processing Works¶ ↑

The operator implementations (see the Operator module) are called first and they ensure that the processing state is consistent. For example, operators that modify the graphics state do actually modify the graphics_state object. However, operator implementations are only used for this task and not more, so they are very specific and normally don’t need to be changed.

After that methods corresponding to the operator names are invoked on the processor object (if they exist). Each PDF operator name is mapped to a nicer message name via the OPERATOR_MESSAGE_NAME_MAP constant. For example, the operator ‘q’ is mapped to ‘save_graphics_state“.

The task of these methods is to do something useful with the content itself, it doesn’t need to concern itself with ensuring the consistency of the processing state. For example, the processor could use the processing state to extract the text. Or paint the content on a canvas.

For inline images only the ‘BI’ operator mapped to ‘inline_image’ is used. Although also the operators ‘ID’ and ‘EI’ exist for inline images, they are not used because they are consumed while parsing inline images and do not reflect separate operators.

Text Processing¶ ↑

Two utility methods decode_text and decode_text_with_positioning for extracting text are provided. Both can directly be invoked from the ‘show_text’ and ‘show_text_with_positioning’ methods.