# Idiomatic Rust bindings for Pdfium

`pdfium-render` provides an idiomatic high-level Rust interface to Pdfium, the C++ PDF library
used by the Google Chromium project. Pdfium can render pages in PDF files to bitmaps, load, edit,
and extract text and images from existing PDF files, and create new PDF files from scratch.

```rust
    use pdfium_render::prelude::*;

    fn export_pdf_to_jpegs(path: &impl AsRef<Path>, password: Option<&str>) -> Result<(), PdfiumError> {
        // Renders each page in the PDF file at the given path to a separate JPEG file.

        // Bind to a Pdfium library in the same directory as our Rust executable;
        // failing that, fall back to using a Pdfium library provided by the operating system.

        let pdfium = Pdfium::new(
            Pdfium::bind_to_library(Pdfium::pdfium_platform_library_name_at_path("./"))
                .or_else(|_| Pdfium::bind_to_system_library())?,
        );

        // Load the document from the given path...

        let document = pdfium.load_pdf_from_file(path, password)?;

        // ... set rendering options that will be applied to all pages...

        let render_config = PdfRenderConfig::new()
            .set_target_width(2000)
            .set_maximum_height(2000)
            .rotate_if_landscape(PdfPageRenderRotation::Degrees90, true);

        // ... then render each page to a bitmap image, saving each image to a JPEG file.

        for (index, page) in document.pages().iter().enumerate() {
            page.render_with_config(&render_config)?
                .as_image() // Renders this page to an image::DynamicImage...
                .as_rgba8() // ... then converts it to an image::Image...
                .ok_or(PdfiumError::ImageError)?
                .save_with_format(
                    format!("test-page-{}.jpg", index), 
                    image::ImageFormat::Jpeg
                ) // ... and saves it to a file.
                .map_err(|_| PdfiumError::ImageError)?;
        }

        Ok(())
    }
```

`pdfium-render` binds to a Pdfium library at run-time, allowing for flexible selection of
system-provided or bundled Pdfium libraries and providing idiomatic Rust error handling in
situations where a Pdfium library is not available. A key advantage of binding to Pdfium at run-time
rather than compile-time is that a Rust application using `pdfium-render` can be compiled to WASM
for running in a browser alongside a WASM-packaged build of Pdfium.

`pdfium-render` aims to eventually provide bindings to all non-interactive functionality provided
by Pdfium. This is a work in progress that will be completed by version 1.0 of this crate.

## Examples

Short, commented examples that demonstrate all the major Pdfium document handling features are
available at <https://github.com/ajrcarey/pdfium-render/tree/master/examples>. These examples demonstrate:

* Rendering pages, and portions of pages, to bitmaps.
* Text and image extraction.
* Form field introspection.
* Document signature introspection.
* Document attachment creation and introspection.
* Document concatenation.
* Page object introspection.
* Page annotation introspection.
* Page link introspection.
* Creation of new documents and new pages.
* Creation of page objects for text, paths, and bitmaps.
* Page object transformation.
* Multi-page tiled rendering.
* Watermarking.
* Thread safety.
* Compiling to WASM.

## What's new

_Note: upcoming release 0.9.0 will remove all deprecated items. For a complete list of deprecated
items, see <https://github.com/ajrcarey/pdfium-render/issues/36>._

Version 0.8.14 corrects a Windows-specific build error introduced in 0.8.13.

Version 0.8.13 corrects a bug in `PdfPageTextObject::chars()` that could see incorrect results
returned in edge cases involving overlapping text objects, and adds the `PdfPageTextSearch`
object and `PdfPageText::search()` function for running text searches across the text of
a single page, thanks to an excellent contribution from <https://github.com/zhonghua-wang>.
A new `examples/text_search.rs` example demonstrates the new search functionality.

Version 0.8.12 adds the `PdfPage::points_to_pixels()` and `PdfPage::pixels_to_points()` functions
for easily converting between the page coordinate system, measured in `PdfPoints`, to the
bitmap rendering coordinate system, measured in `Pixels`. A new `examples/export_clip_crop.rs`
example demonstrates using the conversion functions to precisely clip and crop a target area of
a sample page during rendering.

Version 0.8.11 adds the `PdfAppearanceMode` enum and the `PdfFormFieldCommon::appearance_stream()` and
`PdfFormFieldCommon::appearance_mode_value()` functions, then uses these to improve the
implementations of both `PdfFormRadioButtonField::is_checked()` and `PdfForm::field_values()` to
take appearance streams into account when determining which checkboxes or radio buttons are
selected in an embedded form.

## Binding to Pdfium

`pdfium-render` does not include Pdfium itself. You have several options:

* Bind to a dynamically-built Pdfium library provided by the operating system.
* Bind to a dynamically-built Pdfium library packaged alongside your Rust executable.
* Bind to a statically-built Pdfium library linked to your executable at compile time.

When compiling to WASM, packaging an external build of Pdfium as a separate WASM module is essential.

## Dynamic linking

Binding to a pre-built Pdfium dynamic library at runtime is the simplest option. On Android, a pre-built
`libpdfium.so` is packaged as part of the operating system (although recent versions of Android no
longer permit user applications to access it); alternatively, you can package a dynamic library
appropriate for your operating system alongside your Rust executable.

Pre-built Pdfium dynamic libraries suitable for runtime binding are available from several sources:

* Native (i.e. non-WASM) builds of Pdfium for all major platforms: <https://github.com/bblanchon/pdfium-binaries/releases>
* Android, iOS, macOS, and WASM builds of Pdfium: <https://github.com/paulocoutinhox/pdfium-lib/releases>

If you are compiling a native (i.e. non-WASM) build, and you place an appropriate Pdfium library
in the same folder as your compiled application, then binding to it at runtime is as simple as:

```rust
    use pdfium_render::prelude::*;

    let pdfium = Pdfium::new(
        Pdfium::bind_to_library(Pdfium::pdfium_platform_library_name_at_path("./")).unwrap()
    );
```

A common pattern used in the examples at <https://github.com/ajrcarey/pdfium-render/tree/master/examples>
is to first attempt to bind to a Pdfium library in the same folder as the compiled example, and
attempt to fall back to a system-provided library if that fails:

```rust
    use pdfium_render::prelude::*;

    let pdfium = Pdfium::new(
        Pdfium::bind_to_library(Pdfium::pdfium_platform_library_name_at_path("./"))
            .or_else(|_| Pdfium::bind_to_system_library())
            .unwrap() // Or use the ? unwrapping operator to pass any error up to the caller
    );
```

This pattern is used to provide an implementation of the `Default` trait, so the above can be
written more simply as:

```rust
    use pdfium_render::prelude::*;

    let pdfium = Pdfium::default();
```

## Static linking

The `static` crate feature offers an alternative to dynamic linking if you prefer to link Pdfium
directly into your executable at compile time. This enables the `Pdfium::bind_to_statically_linked_library()`
function which binds directly to the Pdfium functions compiled into your executable:

```rust
    use pdfium_render::prelude::*;

    let pdfium = Pdfium::new(Pdfium::bind_to_statically_linked_library().unwrap());
```

As a convenience, `pdfium-render` can instruct `cargo` to link a statically-built Pdfium
library for you. Set the path to the directory containing your pre-built library using
the `PDFIUM_STATIC_LIB_PATH` environment variable when you run `cargo build`, like so:

```rust
    PDFIUM_STATIC_LIB_PATH="/path/containing/your/static/pdfium/library" cargo build
```

`pdfium-render` will pass the following flags to `cargo`:

```rust
    cargo:rustc-link-lib=static=pdfium
    cargo:rustc-link-search=native=$PDFIUM_STATIC_LIB_PATH
```

This saves you writing a custom `build.rs` yourself. If you have your own build pipeline
that links Pdfium statically into your executable, simply leave the `PDFIUM_STATIC_LIB_PATH`
environment variable unset.

Note that the path you set in `PDFIUM_STATIC_LIB_PATH` should not include the filename of the
library itself; it should just be the path of the containing directory. You must make sure your
statically-built library is named in the appropriate way for your target platform
(`libpdfium.a` on Linux and macOS, for example) in order for the Rust compiler to locate it.

Depending on how your Pdfium library was built, you may need to also link against a C++ standard library.
To link against the GNU C++ standard library (`libstdc++`), use the optional `libstdc++` feature.
`pdfium-render` will pass the following additional flag to `cargo`:

```rust
    cargo:rustc-link-lib=dylib=stdc++
```

To link against the LLVM C++ standard library (`libc++`), use the optional `libc++` feature.
`pdfium-render` will pass the following additional flag to `cargo`:

```rust
    cargo:rustc-link-lib=dylib=c++
```

Alternatively, use the `link-cplusplus` crate to link against a C++ standard library. `link-cplusplus`
offers more options for deciding which standard library should be selected, including automatically
selecting the build platform's installed default.

`pdfium-render` will not build Pdfium for you; you must build Pdfium yourself, or source a
pre-built static archive from elsewhere. For an overview of the build process, including a sample
build script, see <https://github.com/ajrcarey/pdfium-render/issues/53>.

## Compiling to WASM

See <https://github.com/ajrcarey/pdfium-render/tree/master/examples> for a full example that shows
how to bundle a Rust application using `pdfium-render` alongside a pre-built Pdfium WASM module for
inspection and rendering of PDF files in a web browser.

Certain functions that access the file system are not available when compiling to WASM. In all cases,
browser-specific alternatives are provided, as detailed at the link above.

At the time of writing, the WASM builds of Pdfium at <https://github.com/bblanchon/pdfium-binaries/releases>
are compiled with a non-growable WASM heap memory allocator. This means that attempting to open
a PDF document longer than just a few pages will result in an unrecoverable out of memory error.
The WASM builds of Pdfium at <https://github.com/paulocoutinhox/pdfium-lib/releases> are recommended
as they do not have this problem.

## Multi-threading

Pdfium makes no guarantees about thread safety and should be assumed _not_ to be thread safe.
The Pdfium authors specifically recommend that parallel processing, not multi-threading,
be used to process multiple documents simultaneously.

`pdfium-render` achieves thread safety by locking access to Pdfium behind a mutex;
each thread must acquire exclusive access to this mutex in order to make any call to Pdfium.
This has the effect of sequencing all calls to Pdfium as if they were single-threaded,
even when using `pdfium-render` from multiple threads. This approach offers no performance benefit,
but it ensures that Pdfium will not crash when running as part of a multi-threaded application.

An example of safely using `pdfium-render` as part of a multi-threaded parallel iterator is
available at <https://github.com/ajrcarey/pdfium-render/tree/master/examples>.

## Crate features

This crate provides the following optional features:

* `bindings`: uses `cbindgen` to generate Rust bindings to the Pdfium functions defined in the
  `include/*.h` files each time `cargo build` is run. If `cbindgen` or any of its dependencies
  are not available then the build will fail.
* `image`: controls whether the `image` crate should be used by `pdfium-render` to provide page and
  page object rendering functionality. Projects that do not require page or page object rendering
  can disable this feature to avoid compiling the `image` crate into their binaries.
* `libstdc++`: links against the GNU C++ standard library when compiling. Requires the `static` feature. See the "Static linking" section above.
* `libc++`: links against the LLVM C++ standard library when compiling. Requires the `static` feature. See the "Static linking" section above.
* `static`: enables binding to a statically-linked build of Pdfium. See the "Static linking" section above.
* `sync`: provides implementations of the `Send` and `Sync` traits for the `Pdfium` and `PdfDocument`
  structs. This is useful for creating static instances that can be used with `lazy_static` or `once_cell`,
  although those instances are not guaranteed to be thread-safe. Use entirely at your own risk.
  Requires the `thread_safe` feature.
* `thread_safe`: wraps access to Pdfium behind a mutex to ensure thread-safe access to Pdfium.
  See the "Multithreading" section above.

The `image` and `thread_safe` features are enabled by default. All other features are disabled by default.

## Porting existing Pdfium code from other languages

The high-level idiomatic Rust interface provided by `pdfium-render` is built on top of 
raw FFI bindings defined in the `PdfiumLibraryBindings` trait. It is completely feasible to use
these raw FFI bindings directly if you wish, making porting existing code that calls `FPDF_*` functions
trivial while still gaining the benefits of late binding and WASM compatibility.
For instance, the following code snippet (taken from a C++ sample):

```cpp
    string test_doc = "test.pdf";

    FPDF_InitLibrary();
    FPDF_DOCUMENT doc = FPDF_LoadDocument(test_doc, NULL);
    // ... do something with doc
    FPDF_CloseDocument(doc);
    FPDF_DestroyLibrary();
```

would translate to the following Rust code:

```rust
    let bindings = Pdfium::default().bindings();
    
    let test_doc = "test.pdf";

    bindings.FPDF_InitLibrary();
    let doc = bindings.FPDF_LoadDocument(test_doc, None);
    // ... do something with doc
    bindings.FPDF_CloseDocument(doc);
    bindings.FPDF_DestroyLibrary();
```

Pdfium's API uses three different string types: classic C-style null-terminated char arrays,
UTF-8 byte arrays, and a UTF-16LE byte array type named `FPDF_WIDESTRING`. For functions that take a
C-style string or a UTF-8 byte array, `pdfium-render`'s binding will take the standard Rust `&str` type.
For functions that take an `FPDF_WIDESTRING`, `pdfium-render` exposes two functions: the vanilla
`FPDF_*()` function that takes an `FPDF_WIDESTRING`, and an additional `FPDF_*_str()` helper function
that takes a standard Rust `&str` and converts it internally to an `FPDF_WIDESTRING` before calling
Pdfium. Examples of functions with additional `_str()` helpers include `FPDFBookmark_Find()`,
`FPDFText_SetText()`, `FPDFText_FindStart()`, `FPDFDoc_AddAttachment()`, `FPDFAnnot_SetStringValue()`,
and `FPDFAttachment_SetStringValue()`.

The `PdfiumLibraryBindings::get_pdfium_utf16le_bytes_from_str()` and
`PdfiumLibraryBindings::get_string_from_pdfium_utf16le_bytes()` utility functions are provided
for converting to and from `FPDF_WIDESTRING` in your own code.

Some Pdfium functions return classic C-style integer boolean values, aliased as `FPDF_BOOL`.
The `PdfiumLibraryBindings::TRUE()`, `PdfiumLibraryBindings::FALSE()`,
`PdfiumLibraryBindings::is_true()`, and `PdfiumLibraryBindings::bool_to_pdfium()` utility functions
are provided for converting to and from `FPDF_BOOL` in your own code.

Image pixel data in Pdfium is encoded in either three-channel BGR or four-channel BGRA.
The `PdfiumLibraryBindings::bgr_to_rgba()`, `PdfiumLibraryBindings::bgra_to_rgba()`,
`PdfiumLibraryBindings::rgb_to_bgra()`, and `PdfiumLibraryBindings::rgba_to_bgra()` utility functions
are provided for converting between RGB and BGR image data in your own code. 

## Development status

The initial focus of this crate was on rendering pages in a PDF file; consequently, `FPDF_*`
functions related to page rendering were prioritised. By 1.0, the functionality of all
`FPDF_*` functions exported by all Pdfium modules will be available, with the exception of certain
functions specific to interactive scripting, user interaction, and printing.

* Releases numbered 0.4.x added support for basic page rendering Pdfium functions to `pdfium-render`.
* Releases numbered 0.5.x-0.6.x added support for most read-only Pdfium functions to `pdfium-render`.
* Releases numbered 0.7.x added support for most Pdfium page object creation and editing functions to `pdfium-render`. 
* Releases numbered 0.8.x aim to progressively add support for all remaining Pdfium editing functions to `pdfium-render`.
* Releases numbered 0.9.x aim to fill any remaining gaps in the high-level interface prior to 1.0.

There are 368 `FPDF_*` functions in the Pdfium API. As of version 0.8.14, 325 (88%) have
bindings available in `PdfiumLibraryBindings`, with the functionality of the majority of these
available via the `pdfium-render` high-level interface.

Some functions and type definitions in the high-level interface have been renamed or revised since
their initial implementation. The initial implementations are still available but are marked as
deprecated. These deprecated items will be removed in release 0.9.0.

If you need a binding to a Pdfium function that is not currently available, just raise an issue
at <https://github.com/ajrcarey/pdfium-render/issues>.

## Version history

* 0.8.15: adds `PdfPageAnnotationAttachmentPoints` struct and matching iterator; adds new annotation functions
  to `PdfPageAnnotationCommon` along with their matching implementations in `PdfPageAnnotationPrivate`,
  including `PdfPageAnnotationCommon::set_bounds()`, `PdfPageAnnotationCommon::set_position()`,
  `PdfPageAnnotationCommon::set_width()`, `PdfPageAnnotationCommon::set_height()`,
  `PdfPageAnnotationCommon::set_creation_date()`, `PdfPageAnnotationCommon::set_modification_date()`;
  `PdfPageAnnotationCommon::stroke_color()`, `PdfPageAnnotationCommon::set_stroke_color()`,
  `PdfPageAnnotationCommon::fill_color()`, `PdfPageAnnotationCommon::set_fill_color()` functions;
  adds `PdfPageAnnotationCommon::attachment_points()` accessor function; adds conversion from
  `chrono::DateTime` types to PDF date strings in `utils::dates`; adds mutability and annotation
  creation functions to `PdfPageAnnotations` collection; adds new `create_annotations.rs` example.
* 0.8.14: adjusts the `PdfSearchOptions::as_pdfium()` function introduced in 0.8.13 to return
  a `c_ulong` in order to fix a build-time error specific to Windows.
* 0.8.13: addresses incorrect results returned by `PdfPageTextObject::chars()` as
  described in <https://github.com/ajrcarey/pdfium-render/issues/98>; adds new `PdfPageTextSearch` and
  `PdfSearchOptions` objects and new `PdfPageText::search()` function for running text searches
  across the text of a single page, thanks to an excellent contribution from
  <https://github.com/zhonghua-wang>; adds new `examples/text_search.rs` example.
* 0.8.12: improves backwards compatibility with Rust versions prior to 1.62.0 for the
  `PdfAppearanceMode` enum added in 0.8.11 and the `Ord` trait implementation for `PdfPoints`
  added in 0.8.10; adds bindings for `FPDF_PageToDevice()` and `FPDF_DeviceToPage()` coordinate
  system conversion functions; exposes equivalent functionality in the high-level interface
  via new `PdfPage::points_to_pixels()` and `PdfPage::pixels_to_points()` functions;
  adds new `examples/export_clip_crop.rs` example; extends implementation of `Pdfium::default()`
  to try to load a Pdfium library located in the current working directory as well as a system library.
* 0.8.11: adds the `PdfAppearanceMode` enum, the `PdfFormFieldCommon::appearance_stream()` and
  `PdfFormFieldCommon::appearance_mode_value()` functions, supporting internal implementation of
  those functions in `PdfFormFieldPrivate`; improves implementation of `PdfFormRadioButtonField::is_checked()`
  to take appearance streams into account; improves implementation of `PdfForm::field_values()` to
  take control groups into account.
* 0.8.10: adds matrix math operations to `PdfMatrix`; adds `PdfRect::transform()` and `PdfMatrix::apply_to_points()` functions for transforming
  rectangles and points; uses matrix math operations in `PdfMatrix` to simplify implementation
  of `PdfRenderConfig`; adds `PdfPagePathObjectSegments::raw()` and `PdfPagePathObjectSegments::transform()`
  functions to allow iteration over raw or transformed path segment coordinates respectively;
  adds `PdfDestinationViewSettings` enum and `PdfDestination::view()` function for retrieving
  the view settings for an internal document destination.
* 0.8.9: changes `Pdfium::bind_to_library()` and `Pdfium::pdfium_platform_library_name_at_path()`
  to take and return `AsRef<Path>` and `PathBuf` types rather than strings, thanks to an excellent
  contribution from <https://github.com/heimmat>.
* 0.8.8: adjusts `PdfiumRenderWasmState::bind_to_pdfium()` to fall back to `Module["asm"]["malloc"]`
  and `Module["asm"]["free"]` if `Module["_malloc"]` and `Module["_free"]` are not available, in response to
  upstream packaging changes at <https://github.com/paulocoutinhox/pdfium-lib/releases>. For more details,
  see <https://github.com/ajrcarey/pdfium-render/issues/95>.
* 0.8.7: renames `PdfBitmapFormat::BRGx` to `PdfBitmapFormat::BGRx`, deprecating the misspelled
  variant; adds `Send` and `Sync` implementations for `PdfDocument` struct when using the `sync`
  crate feature; adds `Debug` trait implementation to `Pdfium` for better `once_cell` compatibility;
  adds new constants `PdfPoints::MAX`, `PdfPoints::MIN`, and `PdfRect::MAX`; corrects a clipping bug
  in `PdfPage::transform()` and `PdfPage::set_matrix()` by setting the default clipping area to
  `PdfRect::MAX` rather than `PdfPage::size()`. Deprecated items will be removed in release 0.9.0.
* 0.8.6: fixes a bug in `PdfColor::as_pdfium_color()` that resulted in the alpha value being ignored
  when composing the `FPDF_DWORD` representation of the color value; renames `PdfBitmapRotation` enum
  to `PdfPageRenderRotation`, deprecating the old enum; adds convenience functions `PdfColor::mix()`,
  `PdfColor::mix_with()`, `PdfColor::from_hex()`, `PdfColor::to_hex()`, and `PdfColor::to_hex_with_alpha()`;
  adds a wide variety of new color constants to `PdfColor`, deprecating all existing `PdfColor::SOLID_*`
  consts in favour of renamed consts with the `SOLID_` prefix removed; moves `PdfPoints` and `PdfRect`
  structs out into new files; adds `PdfQuadPoints` struct; adds implementations of `Display` to
  `PdfPoints`, `PdfRect`, and `PdfQuadPoints`; fixes a double-free bug in
  `PdfPageImageObject::get_image_from_bitmap_handle()`. Deprecated items will be removed in
  release 0.9.0.
* 0.8.5: adds `PdfDestination::page_index()` function; adds `PdfPageObjectCommon::dash_phase()`
  `PdfPageObjectCommon::set_dash_phase()`, `PdfPageObjectCommon::dash_array()`, and
  `PdfPageObjectCommon::set_dash_array()` functions thanks to an excellent contribution
  from <https://github.com/DorianRudolph>.
* 0.8.4: fixes conditional import of `PdfPoints` struct into `PdfPageImageObject` so it is no longer
  dependent on the `image` crate feature being enabled; corrects a bug in the calculation of rendered
  bitmap pixel dimensions, thanks to an excellent contribution from <https://github.com/slawekkolodziej>.
* 0.8.3: adds `PdfFonts` collection, `PdfDocument::fonts()` and `PdfDocument::fonts_mut()` accessor
  functions, and `PdfFontToken` struct; moves font constructors from `PdfFont` into `PdfFonts`,
  deprecating constructors in `PdfFont`; adds `ToPdfFontToken` trait, along with implementations
  of the trait for `PdfFont`, `&PdfFont`, and `PdfFontToken`; adjusts all functions that previously
  took a `PdfFont` or `&PdfFont` reference so that they now take a `impl ToPdfFontToken`. Deprecated
  items in `PdfFont` will be removed in release 0.9.0.
* 0.8.2: adds `PdfBitmap::from_bytes()` function in response to <https://github.com/ajrcarey/pdfium-render/issues/83>;
  relaxes lifetime requirements on `Pdfium::load_pdf_from_reader()` and related functions
  thanks to an excellent contribution from <https://github.com/bavardage>.
* 0.8.1: changes the data type of `PdfBitmap::Pixels` from `u16` to `c_int` and adds the `PdfBitmap::bytes_required_for_size()`
  helper function in response to <https://github.com/ajrcarey/pdfium-render/issues/80>.
* 0.8.0: removes the ability to acquire an owned `PdfPages` instance from `PdfDocument::pages()`
  as per <https://github.com/ajrcarey/pdfium-render/issues/47>; adds new `PdfDocument::pages_mut()`
  function to match reworked `PdfDocument::pages()` function; fixes a bug in the WASM implementation
  of `FPDFText_GetBoundedText()` as detailed in <https://github.com/ajrcarey/pdfium-render/issues/77>;
  reworks handling of `FPDF_GetLastError()` as detailed in <https://github.com/ajrcarey/pdfium-render/issues/78>.
* 0.7.34: replaces functions in `PdfPageLinks` using linear traversal with binary search traversal;
  adds new `PdfFormField` enum; renames `PdfPageObjectFormFragment` to `PdfPageXObjectFormObject`
  to disambiguate it from `PdfForm` and `PdfFormField`; adds `PdfPageAnnotationCommon::as_form_field()`
  accessor function; adds form field structs `PdfFormPushButtonField`, `PdfFormCheckboxField`,
  `PdfFormComboBoxField`, `PdfFormListBoxField`, `PdfFormRadioButtonField`, `PdfFormSignatureField`,
  `PdfFormTextField`, and `PdfFormUnknownField`; adds `PdfFormFieldOption` struct and
  `PdfFormFieldOptions` collection for retrieving the options displayed within a list box or
  combo box field; adds `PdfFormFieldCommon` and `PdfFormFieldPrivate` traits and associated
  implementations for all `PdfFormField` field types; adds the `PdfForm::field_values()` convenience
  function; adds `examples/form_fields.rs` example.
* 0.7.33: adds the `create_transform_setters!()` and `create_transform_getters!()` private macros,
  ensuring API consistency and maximising code reuse across all transformable objects;
  adds `PdfPage::transform()`, `PdfPage::transform_with_clip()`, and `PdfPage::set_matrix_with_clip()`
  functions; adds `examples/matrix.rs` example; adds bindings for remaining `FPDF_*ClipPath*()` functions.
* 0.7.32: fixes off-by-one errors in `PdfPageText::chars_inside_rect()` and `examples/chars.rs`
  thanks to an excellent contribution from <https://github.com/luketpeterson>, adds support
  for grayscale image processing to `PdfPageImageObject::get_image_from_bitmap_handle()` thanks
  to an excellent contribution from <https://github.com/stephenjudkins>, and corrects a missing
  dependency when using `pdfium-render` without the default `image` crate feature.
* 0.7.31: adds the `PdfPageLinks` collection, the `PdfPage::links()` and `PdfPage::links_mut()`
  functions, the `PdfLink` and `PdfDestination` structs, the `PdfActionCommon` and `PdfActionPrivate`
  traits, structs for the action types supported by Pdfium, the `PdfActionUri::uri()` function
  to address <https://github.com/ajrcarey/pdfium-render/issues/68>, and the new `examples/links.rs` example.
* 0.7.30: deprecates the `PdfPages::delete_page_at_index()` and `PdfPages::delete_page_range()` functions;
  adds `PdfPage::delete()` function in response to <https://github.com/ajrcarey/pdfium-render/issues/67>.
  Deprecated items will be removed in release 0.9.0, although it may be possible to restore these
  functions if safer reference handling in `PdfDocument` and `PdfPages` is introduced as part of
  <https://github.com/ajrcarey/pdfium-render/issues/47>.
* 0.7.29: removes the `sync` crate feature from the list of default crate features in response
  to <https://github.com/ajrcarey/pdfium-render/issues/66>.
* 0.7.28: removes the `PdfPageObjects::take_*()` functions; adds `PdfPageObject::is_copyable()`
  `PdfPageObject::try_copy()`, `PdfPageObjectGroup::retain()`, `PdfPageObjectGroup::retain_if_copyable()`,
  `PdfPageObjectGroup::is_copyable()`, `PdfPageObjectGroup::try_copy_onto_existing_page()`,
  `PdfPageObjectGroup::copy_onto_new_page_at_start()`,
  `PdfPageObjectGroup::copy_onto_new_page_at_end()`, and
  `PdfPageObjectGroup::copy_onto_new_page_at_index()` functions;
  adds `examples/copy_objects.rs` example; fixes a bug in the propagation of a page's content
  regeneration strategy; removes all use of `lazy_static!` macro in favour of `once_cell::sync::Lazy`.
* 0.7.27: adjusts `examples/index.html` to take into account upstream packaging changes in the
  WASM builds of Pdfium published at <https://github.com/paulocoutinhox/pdfium-lib/releases>;
  adds the `image` crate feature.
* 0.7.26: adds `sync` default crate feature providing `Send` and `Sync` implementations for `Pdfium`
  struct; adds `Display` and `Error` trait implementations to `PdfiumError` for `anyhow` compatibility;
  adjusts WASM example to account for upstream changes in Emscripten packaging of Pdfium WASM builds;
  corrects a lifetime problem in `Pdfium::load_pdf_from_bytes()` and deprecates `Pdfium::load_pdf_from_bytes()`
  in favour of `Pdfium::load_pdf_from_byte_slice()` and `Pdfium::load_pdf_from_byte_vec()`.
  Deprecated items will be removed in release 0.9.0.
* 0.7.25: adds the `PdfPageAnnotationObjects` collection and the `PdfPageAnnotation::objects()`,
  `PdfPageInkAnnotation::objects_mut()`, and `PdfPageStampAnnotation::objects_mut()` functions
  to the high-level interface.
* 0.7.24: adds bindings for `FPDFClipPath_CountPathSegments()`, `FPDFClipPath_GetPathSegment()`,
  `FPDFPath_CountSegments()`, `FPDFPath_GetPathSegment()`, and `FPDFPathSegment_*()` functions;
  adds `PdfFontGlyphs` and `PdfPagePathObjectSegments` collections to the high-level interface,
  along with accessor functions in `PdfFont` and `PdfPagePathObject`; adds the `PdfPathSegments` trait;
  introduces some infrastructure necessary for the future implementation of a `PdfClipPath` object;
  adds `PdfPages::first()`, `PdfPages::last()`, and `PdfPage::fonts()` convenience functions.
* 0.7.23: removes some unnecessary mutable bindings in `PdfBitmap`; uses `#[cfg(doc)]` declarations
  to ensure `cargo doc` generates documentation for all functionality, irrespective of the platform.
* 0.7.22: attempts to work around two problems in Pdfium's bitmap generation when retrieving
  processed renderings of page image objects. See <https://github.com/ajrcarey/pdfium-render/issues/52>
  for more information.
* 0.7.21: adds bindings for `FPDF_GetPageAAction()`, `FPDF_GetFileIdentifier()`, and all remaining
  `FPDFDest_*()` and `FPDFLink_*()` functions; adds `PdfAttachment::len()` and
  `PdfAttachment::is_empty()` convenience functions; adds `libstdc++` and `libc++` crate features;
  adds color conversion functions to `PdfiumLibraryBindings`; corrects bugs in color conversion
  when working with `PdfPageImageObject`, as detailed in <https://github.com/ajrcarey/pdfium-render/issues/50>;
  fixes a bug in the WASM implementation of `FPDFAnnot_GetAttachmentPoints()`; corrects
  some small typos in examples.
* 0.7.20: adds bindings for `FPDFPage_*Thumbnail*()`, `FPDFLink_*()`, and `FPDFText_Find*()` functions;
  adds `PdfAttachments::create_attachment_from_bytes()`, `PdfAttachments::create_attachment_from_file()`,
  `PdfAttachments::create_attachment_from_reader()`, `PdfAttachments::create_attachment_from_fetch()`,  
  `PdfAttachments::create_attachment_from_blob()`, `PdfAttachments::delete_at_index()`,
  `PdfAttachment::save_to_writer()`, `PdfAttachment::save_to_file()`, `PdfAttachment::save_to_blob()`,
  `PdfPage::has_embedded_thumbnail()`, `PdfPage::embedded_thumbnail()`, and `PdfPage::boundaries_mut()`
  functions to the high-level interface; renames `PdfAttachment::bytes()` function introduced in 0.7.19
  to `PdfAttachment::save_to_bytes()`.
* 0.7.19: adds bindings for `FPDFDoc_*Attachment*()` functions; adds `PdfAttachments` and
  `PdfSignatures` collections to the high-level interface.
* 0.7.18: adds convenience `bindings()` accessor functions to `PdfDocument`, `PdfPage`, `PdfBitmap`,
  `PdfFont`, and various other interfaces, thanks to an excellent contribution from
  <https://github.com/LU15W1R7H>; deprecates `Pdfium::get_bindings()` in favour of
  `Pdfium::bindings()` for consistency. Deprecated items will be removed in release 0.9.0.
* 0.7.17: relaxes some unnecessarily restrictive lifetime bounds in `PdfPageObjectPath`. 
* 0.7.16: adds `PdfPageObjects::create_path_object_bezier()` and `PdfPageObjectPath::new_bezier()`
  convenience functions; corrects some typos in documentation.
* 0.7.15: adds `PdfPageAnnotationCommon::name()`, `PdfPageAnnotationCommon::contents()`,
  `PdfPageAnnotationCommon::author()`, `PdfPageAnnotationCommon::creation_date()`,
  and `PdfPageAnnotationCommon::modification_date()` functions for working with annotations;
  adds `PdfPageText::for_annotation()` and `PdfPageText::chars_for_annotation()` for more easily
  extracting text and characters associated with annotations; adds `examples/annotations.rs` and
  `examples/image_extract.rs`; renames `examples/text.rs` to `examples/text_extract.rs`.
* 0.7.14: fixes a bug in the WASM implementation of `FPDF_StructElement_GetStringAttribute()`;
  pins required version of `image` crate to at least 0.24.0 or later to avoid incompatibility between
  the `image::DynamicImage` trait definitions in 0.23.x and 0.24.x; adds compatibility with web workers
  to the WASM implementation, thanks to an excellent contribution from <https://github.com/NyxCode>.
* 0.7.13: adds transformation and clipping functions to `PdfRenderConfig`; adds bindings for
  `FPDF_RenderPageBitmapWithMatrix()`; deprecates `PdfRenderConfig::rotate_if_portait()`
  in favour of the correctly-spelled `PdfRenderConfig::rotate_if_portrait()`. 
  Deprecated items will be removed in release 0.9.0.
* 0.7.12: adds `PdfPage::render_into_bitmap()` and `PdfPage::render_into_bitmap_with_config()`
  functions for higher performance; deprecates `PdfPage::get_bitmap()` in favour of `PdfPage::render()`;
  deprecates `PdfPage::get_bitmap_with_config()` in favour of `PdfPage::render_with_config()`;
  deprecates `PdfBitmapConfig` in favour of `PdfRenderConfig`; deprecates `PdfBitmap::render()`
  as the function is no longer necessary. Deprecated items will be removed in release 0.9.0.
* 0.7.11: adds the new WASM-specific `PdfBitmap::as_array()` function as a higher performance
  alternative to the cross-platform `PdfBitmap::as_bytes()` function, thanks to an excellent
  contribution from <https://github.com/NyxCode>.
* 0.7.10: corrects some typos in documentation; adds additional constructors to `PdfPageImageObject`
  that apply a specified width and/or height at object creation time.
* 0.7.9: adds retrieval of the list of image filters applied to a `PdfPageImageObject`;
  adds the `PdfColorSpace` enum; adds bindings for the `FPDF_*Signature*()`, `FPDFSignatureObj_*()`,
  and `FPDF_StructTree_*()` functions.
* 0.7.8: adds image support to the `PdfPageImageObject` struct, the `PdfPageObjects::add_image_object()`
  and `PdfPageObjects::create_image_object()` functions, additional convenience functions for
  loading fonts from files and readers to `PdfFont`, and bindings for `FPDF_VIEWERREF_Get*()` functions.
* 0.7.7: adds the `thread_safe` crate feature and the accompanying example in `examples/thread_safe.rs`.
* 0.7.6: adds retrieval of text settings on a character-by-character basis to the `PdfPageText` and
  `PdfPageTextObject` objects; adds `PdfPageTextSegment` and `PdfPageTextChar` structs to the 
  high-level interface; adds retrieval of current transformation settings to all page objects;
  adds the `PdfPageTextObject::scaled_font_size()` function and renames `PdfPageTextObject::font_size()`
  to `PdfPageTextObject::unscaled_font_size()` as these names make clearer the differences between
  scaled and unscaled font sizes in text objects; adds bindings for all remaining `FPDFText_*()` functions.
* 0.7.5: corrects a bug in error handling on Windows. See <https://github.com/ajrcarey/pdfium-render/issues/24>
  for more information.
* 0.7.4: adds the `PdfPageGroupObject::remove_objects_from_page()` function; renamed
  `PdfPageObjects::delete_object()` and `PdfPageObjects::delete_object_at_index()` functions to
  `PdfPageObjects::remove_object()` and `PdfPageObjects::remove_object_at_index()` as these
  names better reflect the underlying operation that occurs.
* 0.7.3: corrects a bug in the implementation of `PdfPages::append()` introduced in 0.7.2. 
* 0.7.2: adds object groups for manipulating and transforming groups of page objects as if they
  were a single object, and the `PdfPages::watermark()` function for applying individualized
  watermarks to any or all pages in a document. Fixes a potential double-free bug in `PdfFont::drop()`.
* 0.7.1: adds path segment creation to the `PdfPagePathObject` object, convenience functions for
  quickly creating rectangles, ellipses, and circles, and the `PdfPageObjects::add_path_object()` function.
* 0.7.0: adds `PdfPermissions` collection, adds document loading and saving support, adds
  initial creation and editing support for documents, pages, and text objects,
  and improves WASM document file handling.
* 0.6.0: fixes some typos in documentation, updates upstream Pdfium WASM package source repository name.
* 0.5.9: corrects a bug in the statically linked bindings implementation. Adjusted tests
  to cover both dynamic and statically linked bindings implementations.
* 0.5.8: corrects a bug in the WASM implementation of certain `FPDFAnnot_*()` functions. Resolves
  a potential memory leak affecting the WASM implementation of various `FPDF_*()` functions.
* 0.5.7: adds support for binding to a statically-linked build of Pdfium, adds `bindgen` and `static` crate features.
* 0.5.6: adds `pdfium_render::prelude`, adds bindings for `FPDFAnnot_*()` and `FPDFPage_*Annot*()`
  functions, adds `PdfPageAnnotations` collection and `PdfPageAnnotation` struct
  to the high-level interface.
* 0.5.5: fixes two bugs in the WASM implementation, one to do with colors,
  one to do with text extraction.
  See <https://github.com/ajrcarey/pdfium-render/issues/9> and
  <https://github.com/ajrcarey/pdfium-render/issues/11> for more information.
* 0.5.4: changes default setting of `PdfBitmapConfig::set_reverse_byte_order()` to `true` to
  switch from Pdfium's default BGRA8 pixel format to RGBA8. This is necessary since
  the `image` crate dropped support for BGRA8 in version 0.24. See
  <https://github.com/ajrcarey/pdfium-render/issues/9> for more information.
* 0.5.3: adds bindings for `FPDFBookmark_*()`, `FPDFPageObj_*()`, `FPDFText_*()`, and
  `FPDFFont_*()` functions, adds `PdfPageObjects`, `PdfPageText`, and `PdfBookmarks` collections
  to the high-level interface.
* 0.5.2: adds bindings for `FPDF_GetPageBoundingBox()`, `FPDFDoc_GetPageMode()`,
  `FPDFPage_Get*Box()`, and `FPDFPage_Set*Box()` functions, adds `PdfPageBoundaries` collection
  to the high-level interface.
* 0.5.1: adds bindings for `FPDFPage_GetRotation()` and `FPDFPage_SetRotation()` functions,
  adds `PdfMetadata` collection to the high-level interface.
* 0.5.0: adds rendering of annotations and form field elements, thanks to an excellent contribution
  from <https://github.com/inzanez>.
* 0.4.2: bug fixes in `PdfBitmapConfig` implementation.
* 0.4.1: improvements to documentation and READMEs.
* 0.4.0: initial release of minimal page rendering functionality.
