pdfium_render/pdf/

bitmap.rs

//! Defines the [PdfBitmap] struct, a bitmap image with a specific width and height.

use crate::bindgen::{
    FPDFBitmap_BGR, FPDFBitmap_BGRA, FPDFBitmap_BGRx, FPDFBitmap_Gray, FPDFBitmap_Unknown,
    FPDF_BITMAP,
};
use crate::bindings::PdfiumLibraryBindings;
use crate::error::{PdfiumError, PdfiumInternalError};
use crate::pdf::document::page::render_config::PdfPageRenderSettings;
use crate::pdfium::PdfiumLibraryBindingsAccessor;
use crate::utils::pixels::{aligned_bgr_to_rgba, aligned_rgb_to_rgba, bgra_to_rgba};
use std::marker::PhantomData;
use std::os::raw::c_int;

#[cfg(feature = "image_025")]
use image_025::{DynamicImage, GrayImage, RgbaImage};

#[cfg(feature = "image_024")]
use image_024::{DynamicImage, GrayImage, RgbaImage};

#[cfg(feature = "image_023")]
use image_023::{DynamicImage, GrayImage, RgbaImage};

#[cfg(not(target_arch = "wasm32"))]
use std::os::raw::c_void;

#[cfg(target_arch = "wasm32")]
use {
    js_sys::Uint8Array,
    wasm_bindgen::{Clamped, JsValue},
    web_sys::ImageData,
};

// The following dummy declarations are used only when running cargo doc.
// They allow documentation of WASM-specific functionality to be included
// in documentation generated on non-WASM targets.

#[cfg(doc)]
struct Uint8Array;

#[cfg(doc)]
struct ImageData;

#[cfg(doc)]
struct JsValue;

/// The device coordinate system when rendering or displaying an image.
///
/// While Pdfium will accept pixel sizes in either dimension up to the limits of [i32],
/// in practice the maximum size of a bitmap image is limited to approximately 2,320,723,080 bytes
/// (a little over 2 Gb). You can use the [PdfBitmap::bytes_required_for_size] function
/// to estimate the maximum size of a bitmap image for a given target pixel width and height.
pub type Pixels = i32;

/// The pixel format of the rendered image data in the backing buffer of a [PdfBitmap].
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum PdfBitmapFormat {
    Gray = FPDFBitmap_Gray as isize,
    BGR = FPDFBitmap_BGR as isize,
    BGRx = FPDFBitmap_BGRx as isize,
    BGRA = FPDFBitmap_BGRA as isize,
}

impl PdfBitmapFormat {
    #[inline]
    #[allow(non_upper_case_globals)]
    pub(crate) fn from_pdfium(format: u32) -> Result<Self, PdfiumError> {
        match format {
            FPDFBitmap_Unknown => Err(PdfiumError::UnknownBitmapFormat),
            FPDFBitmap_Gray => Ok(PdfBitmapFormat::Gray),
            FPDFBitmap_BGR => Ok(PdfBitmapFormat::BGR),
            FPDFBitmap_BGRx => Ok(PdfBitmapFormat::BGRx),
            FPDFBitmap_BGRA => Ok(PdfBitmapFormat::BGRA),
            _ => Err(PdfiumError::UnknownBitmapFormat),
        }
    }

    #[inline]
    pub(crate) fn as_pdfium(&self) -> u32 {
        match self {
            PdfBitmapFormat::Gray => FPDFBitmap_Gray,
            PdfBitmapFormat::BGR => FPDFBitmap_BGR,
            PdfBitmapFormat::BGRx => FPDFBitmap_BGRx,
            PdfBitmapFormat::BGRA => FPDFBitmap_BGRA,
        }
    }
}

// Deriving Default for enums is experimental. We implement the trait ourselves
// to provide better compatibility with older Rust versions.
#[allow(clippy::derivable_impls)]
impl Default for PdfBitmapFormat {
    #[inline]
    fn default() -> Self {
        PdfBitmapFormat::BGRA
    }
}

/// A bitmap image with a specific width and height.
pub struct PdfBitmap<'a> {
    handle: FPDF_BITMAP,
    was_byte_order_reversed_during_rendering: bool,
    lifetime: PhantomData<&'a FPDF_BITMAP>,
}

impl<'a> PdfBitmap<'a> {
    /// Wraps an existing `FPDF_BITMAP` handle inside a new [PdfBitmap].
    pub(crate) fn from_pdfium(handle: FPDF_BITMAP) -> Self {
        PdfBitmap {
            handle,
            was_byte_order_reversed_during_rendering: false,
            lifetime: PhantomData,
        }
    }

    /// Creates an empty [PdfBitmap] with a buffer capable of storing an image of the given
    /// pixel width and height in the given pixel format.
    pub fn empty(
        width: Pixels,
        height: Pixels,
        format: PdfBitmapFormat,
        bindings: &'a dyn PdfiumLibraryBindings,
    ) -> Result<PdfBitmap<'a>, PdfiumError> {
        let handle = unsafe {
            bindings.FPDFBitmap_CreateEx(
                width as c_int,
                height as c_int,
                format.as_pdfium() as c_int,
                std::ptr::null_mut(),
                0, // Not relevant because Pdfium will create the buffer itself.
            )
        };

        if handle.is_null() {
            Err(PdfiumError::PdfiumLibraryInternalError(
                PdfiumInternalError::Unknown,
            ))
        } else {
            Ok(Self::from_pdfium(handle))
        }
    }

    /// Creates a new [PdfBitmap] that wraps the given byte buffer. The buffer must be capable
    /// of storing an image of the given pixel width and height in the given pixel format,
    /// otherwise a buffer overflow may occur during rendering.
    ///
    /// This function is not available when compiling to WASM.
    ///
    /// # Safety
    ///
    /// This function is unsafe because a buffer overflow may occur during rendering if the buffer
    /// is too small to store a rendered image of the given pixel dimensions.
    #[cfg(not(target_arch = "wasm32"))]
    pub unsafe fn from_bytes(
        width: Pixels,
        height: Pixels,
        format: PdfBitmapFormat,
        buffer: &'a mut [u8],
        bindings: &'a dyn PdfiumLibraryBindings,
    ) -> Result<PdfBitmap<'a>, PdfiumError> {
        let handle = bindings.FPDFBitmap_CreateEx(
            width as c_int,
            height as c_int,
            format.as_pdfium() as c_int,
            buffer.as_mut_ptr() as *mut c_void,
            0, // Not relevant because Pdfium will compute the stride value itself.
        );

        if handle.is_null() {
            Err(PdfiumError::PdfiumLibraryInternalError(
                PdfiumInternalError::Unknown,
            ))
        } else {
            Ok(Self::from_pdfium(handle))
        }
    }

    /// Returns the internal `FPDF_BITMAP` handle for this [PdfBitmap].
    #[inline]
    pub(crate) fn handle(&self) -> FPDF_BITMAP {
        self.handle
    }

    /// Lets this [PdfBitmap] know whether it was created from a rendering configuration
    /// that instructed Pdfium to reverse the byte order of generated image data from its
    /// default of BGR8 to RGB8. The setting of this flag determines the color channel
    /// normalization strategy used by [PdfBitmap::as_rgba_bytes].
    #[inline]
    pub(crate) fn set_byte_order_from_render_settings(&mut self, settings: &PdfPageRenderSettings) {
        self.was_byte_order_reversed_during_rendering = settings.is_reversed_byte_order_flag_set
    }

    /// Returns the width of the image in the bitmap buffer backing this [PdfBitmap].
    #[inline]
    pub fn width(&self) -> Pixels {
        (unsafe { self.bindings().FPDFBitmap_GetWidth(self.handle()) }) as Pixels
    }

    /// Returns the height of the image in the bitmap buffer backing this [PdfBitmap].
    #[inline]
    pub fn height(&self) -> Pixels {
        (unsafe { self.bindings().FPDFBitmap_GetHeight(self.handle()) }) as Pixels
    }

    /// Returns the pixel format of the image in the bitmap buffer backing this [PdfBitmap].
    #[inline]
    pub fn format(&self) -> Result<PdfBitmapFormat, PdfiumError> {
        PdfBitmapFormat::from_pdfium(
            unsafe { self.bindings().FPDFBitmap_GetFormat(self.handle()) } as u32,
        )
    }

    /// Returns an immutable reference to the bitmap buffer backing this [PdfBitmap].
    ///
    /// Unlike [PdfBitmap::as_rgba_bytes], this function does not attempt any color channel normalization.
    /// To adjust color channels in your own code, use the [PdfiumLibraryBindings::bgr_to_rgba],
    /// [PdfiumLibraryBindings::bgra_to_rgba], [PdfiumLibraryBindings::rgb_to_bgra],
    /// and [PdfiumLibraryBindings::rgba_to_bgra] functions.
    pub fn as_raw_bytes(&self) -> Vec<u8> {
        unsafe { self.bindings().FPDFBitmap_GetBuffer_as_vec(self.handle) }
    }

    /// Returns an owned copy of the bitmap buffer backing this [PdfBitmap], normalizing all
    /// color channels into RGBA irrespective of the original pixel format.
    pub fn as_rgba_bytes(&self) -> Vec<u8> {
        let bytes = self.as_raw_bytes();

        let format = self.format().unwrap_or_default();

        let width = self.width() as usize;

        let stride = bytes.len() / self.height() as usize;

        if self.was_byte_order_reversed_during_rendering {
            // The R and B channels were swapped by Pdfium during rendering, as configured by
            // a call to PdfRenderConfig::set_reverse_byte_order(true).

            match format {
                PdfBitmapFormat::BGRA | PdfBitmapFormat::BGRx => {
                    // No color conversion necessary; data was already swapped from BGRx
                    // to four-channel RGB during rendering.
                    bytes
                }
                PdfBitmapFormat::BGR => aligned_rgb_to_rgba(bytes.as_slice(), width, stride),
                PdfBitmapFormat::Gray => bytes,
            }
        } else {
            match format {
                PdfBitmapFormat::BGRA | PdfBitmapFormat::BGRx => bgra_to_rgba(bytes.as_slice()),
                PdfBitmapFormat::BGR => aligned_bgr_to_rgba(bytes.as_slice(), width, stride),
                PdfBitmapFormat::Gray => bytes,
            }
        }
    }

    /// Returns a new `Image::DynamicImage` created from the bitmap buffer backing this [PdfBitmap].
    ///
    /// This function is only available when this crate's `image` feature is enabled.
    #[cfg(feature = "image_api")]
    pub fn as_image(&self) -> Result<DynamicImage, PdfiumError> {
        let bytes = self.as_rgba_bytes();

        let width = self.width() as u32;

        let height = self.height() as u32;

        let image = match self.format().unwrap_or_default() {
            PdfBitmapFormat::BGRA | PdfBitmapFormat::BGRx | PdfBitmapFormat::BGR => {
                RgbaImage::from_raw(width, height, bytes).map(DynamicImage::ImageRgba8)
            }
            PdfBitmapFormat::Gray => {
                GrayImage::from_raw(width, height, bytes).map(DynamicImage::ImageLuma8)
            }
        };

        match image {
            Some(image) => Ok(image),
            None => Err(PdfiumError::ImageError),
        }
    }

    /// Returns a Javascript `Uint8Array` object representing the bitmap buffer backing
    /// this [PdfBitmap].
    ///
    /// This function avoids a memory allocation and copy required by both
    /// [PdfBitmap::as_rgba_bytes] and [PdfBitmap::as_image_data], making it preferable for
    /// situations where performance is paramount.
    ///
    /// Unlike [PdfBitmap::as_rgba_bytes], this function does not attempt any color channel normalization.
    /// To adjust color channels in your own code, use the [PdfiumLibraryBindings::bgr_to_rgba],
    /// [PdfiumLibraryBindings::bgra_to_rgba], [PdfiumLibraryBindings::rgb_to_bgra],
    /// and [PdfiumLibraryBindings::rgba_to_bgra] functions.
    ///
    /// This function is only available when compiling to WASM.
    #[cfg(any(doc, target_arch = "wasm32"))]
    #[inline]
    pub fn as_array(&self) -> Uint8Array {
        unsafe { self.bindings().FPDFBitmap_GetBuffer_as_array(self.handle()) }
    }

    /// Returns a new Javascript `ImageData` object created from the bitmap buffer backing
    /// this [PdfBitmap]. The resulting `ImageData` can be easily displayed in an
    /// HTML `<canvas>` element like so:
    ///
    /// `canvas.getContext('2d').putImageData(image_data);`
    ///
    /// This function is slower than calling [PdfBitmap::as_array] because it must perform
    /// an additional memory allocation in order to create the `ImageData` object. Consider calling
    /// the [PdfBitmap::as_array] function directly if performance is paramount.
    ///
    /// This function is only available when compiling to WASM.
    #[cfg(any(doc, target_arch = "wasm32"))]
    #[inline]
    pub fn as_image_data(&self) -> Result<ImageData, JsValue> {
        ImageData::new_with_u8_clamped_array_and_sh(
            Clamped(&self.as_rgba_bytes()),
            self.width() as u32,
            self.height() as u32,
        )
    }

    /// Estimates the maximum memory buffer size required for a [PdfBitmap] of the given dimensions.
    ///
    /// Certain platforms, architectures, and operating systems may limit the maximum size of a
    /// bitmap buffer that can be created by Pdfium.
    ///
    /// The returned value assumes four bytes of memory will be consumed for each rendered pixel.
    #[inline]
    pub fn bytes_required_for_size(width: Pixels, height: Pixels) -> usize {
        4 * width as usize * height as usize
    }
}

impl<'a> Drop for PdfBitmap<'a> {
    /// Closes this [PdfBitmap], releasing the memory held by the bitmap buffer.
    #[inline]
    fn drop(&mut self) {
        unsafe {
            self.bindings().FPDFBitmap_Destroy(self.handle());
        }
    }
}

impl<'a> PdfiumLibraryBindingsAccessor<'a> for PdfBitmap<'a> {}

#[cfg(feature = "thread_safe")]
unsafe impl<'a> Send for PdfBitmap<'a> {}

#[cfg(feature = "thread_safe")]
unsafe impl<'a> Sync for PdfBitmap<'a> {}

#[cfg(test)]
mod tests {
    use crate::prelude::*;
    use crate::utils::mem::create_sized_buffer;
    use crate::utils::test::test_bind_to_pdfium;

    #[test]
    fn test_from_bytes() -> Result<(), PdfiumError> {
        let pdfium = test_bind_to_pdfium();

        let test_width = 2000;
        let test_height = 4000;

        let mut buffer =
            create_sized_buffer(PdfBitmap::bytes_required_for_size(test_width, test_height));

        let buffer_ptr = buffer.as_ptr();

        let bitmap = unsafe {
            PdfBitmap::from_bytes(
                test_width,
                test_height,
                PdfBitmapFormat::BGRx,
                buffer.as_mut_slice(),
                pdfium.bindings(),
            )?
        };

        assert_eq!(bitmap.width(), test_width);
        assert_eq!(bitmap.height(), test_height);
        assert_eq!(
            unsafe { pdfium.bindings().FPDFBitmap_GetBuffer(bitmap.handle) } as usize,
            buffer_ptr as usize
        );
        assert_eq!(
            unsafe { pdfium.bindings().FPDFBitmap_GetStride(bitmap.handle) },
            // The stride length is always a multiple of four bytes; for image formats
            // that require less than four bytes per pixel, the extra bytes serve as
            // alignment padding. For this test, we use the PdfBitmapFormat::BGRx which
            // consumes four bytes per pixel, so test_width * 4 should indeed match
            // the returned stride length.
            test_width * 4
        );

        Ok(())
    }
}