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#[macro_use]
extern crate lopdf;
use lopdf::content::{Content, Operation};
use lopdf::{Document, Object, Stream};
fn main() {
// with_version specifes the PDF version this document complies with.
let mut doc = Document::with_version("1.5");
// Object IDs are used for cross referencing in PDF documents.
// `lopdf` helps keep track of them for us. They are simple integers.
// Calls to `doc.new_object_id` and `doc.add_object` return an object IDs.
// "Pages" is the root node of the page tree
let pages_id = doc.new_object_id();
// fonts are dictionaries. The type, subtype and basefont tags
// are straight out of the PDF reference manual
//
// The dictionary macro is a helper that allows complex
// key, value relationships to be represented in a simpler
// visual manner, similar to a match statement.
// A dictionary is implemented as an IndexMap of Vec<u8>, and Object
let font_id = doc.add_object(dictionary! {
// type of dictionary
"Type" => "Font",
// type of font, type1 is simple postscript font
"Subtype" => "Type1",
// basefont is postscript name of font for type1 font.
// See PDF reference document for more details
"BaseFont" => "Courier",
});
// Font dictionaries need to be added into resource dictionaries in order
// to be used. Resource dictionaries can contain more than just fonts,
// but normally just contains fonts.
// Only one resource dictionary is allowed per page tree root
let resources_id = doc.add_object(dictionary! {
// Fonts are actually triplely nested dictionaries. Fun!
"Font" => dictionary! {
// F1 is the font name used when writing text.
// It must be unique in the document. It does not
// have to be F1
"F1" => font_id,
},
});
// Content is a wrapper struct around an operations struct that contains a vector of operations
// The operations struct contains a vector of operations that match up with a particular PDF
// operator and operands.
// Refer to the PDF spec for more details on these operators and operands.
// Note, the operators and operands are specified in a reverse order than they
// actually appear in the PDF file itself.
let content = Content {
operations: vec![
// BT begins a text element. it takes no operands
Operation::new("BT", vec![]),
// Tf specifies the font and font size. Font scaling is complicated in PDFs.
// Refer to the PDF spec for more info.
// The `into()` methods convert the types into
// an enum that represents the basic object types in PDF documents.
Operation::new("Tf", vec!["F1".into(), 48.into()]),
// Td adjusts the translation components of the text matrix. When used for the first
// time after BT, it sets the initial text position on the page.
// Note: PDF documents have Y=0 at the bottom. Thus 600 to print text near the top.
Operation::new("Td", vec![100.into(), 600.into()]),
// Tj prints a string literal to the page. By default, this is black text that is
// filled in. There are other operators that can produce various textual effects and
// colors
Operation::new("Tj", vec![Object::string_literal("Hello World!")]),
// ET ends the text element
Operation::new("ET", vec![]),
],
};
// Streams are a dictionary followed by a sequence of bytes. What that sequence of bytes
// represents, depends on context.
// The stream dictionary is set internally by lopdf and normally doesn't
// need to be manually nanipulated. It contains keys such as
// Length, Filter, DecodeParams, etc.
let content_id = doc.add_object(Stream::new(dictionary! {}, content.encode().unwrap()));
// Page is a dictionary that represents one page of a PDF file.
// Its required fields are "Type", "Parent" and "Contents".
let page_id = doc.add_object(dictionary! {
"Type" => "Page",
"Parent" => pages_id,
"Contents" => content_id,
});
// Again, pages is the root of the page tree. The ID was already created
// at the top of the page, since we needed it to assign to the parent element of the page
// dictionary
//
// These are just the basic requirements for a page tree root object. There are also many
// additional entries that can be added to the dictionary if needed. Some of these can also be
// defined on the page dictionary itself, and not inherited from the page tree root.
let pages = dictionary! {
// Type of dictionary
"Type" => "Pages",
// Vector of page IDs in document. Normally would contain more than one ID and be produced
// using a loop of some kind
"Kids" => vec![page_id.into()],
// Page count
"Count" => 1,
// ID of resources dictionary, defined earlier
"Resources" => resources_id,
// a rectangle that defines the boundaries of the physical or digital media. This is the
// "Page Size"
"MediaBox" => vec![0.into(), 0.into(), 595.into(), 842.into()],
};
// using insert() here, instead of add_object() since the id is already known.
doc.objects.insert(pages_id, Object::Dictionary(pages));
// Creating document catalog.
// There are many more entries allowed in the catalog dictionary.
let catalog_id = doc.add_object(dictionary! {
"Type" => "Catalog",
"Pages" => pages_id,
});
// Root key in trailer is set here to ID of document catalog,
// remainder of trailer is set during doc.save().
doc.trailer.set("Root", catalog_id);
doc.compress();
// Store file in current working directory.
doc.save("example.pdf").unwrap();
}