pdfcraft/vendor/hayro-interpret/examples/extract_images.rs

//! This example demonstrates how you can extract all images used on a page and save them as
//! PNG.
//!
//! Note that you must have downloaded the corresponding PDF file for the example to work.

use hayro_interpret::font::Glyph;
use hayro_interpret::{
    BlendMode, ClipPath, Context, Device, GlyphDrawMode, Image, ImageData, InterpreterCache,
    InterpreterSettings, Paint, PathDrawMode, SoftMask, interpret_page,
};
use hayro_syntax::Pdf;
use image::{DynamicImage, ImageBuffer};
use kurbo::{Affine, BezPath, Rect};
use std::path::PathBuf;

fn main() {
    let data = std::fs::read(
        PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../hayro-tests/pdfs/custom/image_rgb8.pdf"),
    )
    .unwrap();

    let pdf = Pdf::new(data).unwrap();

    let mut extractor = ImageExtractor::new();
    let settings = InterpreterSettings::default();
    let cache = InterpreterCache::new();
    // Pass dummy values for bbox and initial transform, since we don't care about those.
    let mut context = Context::new(
        Affine::IDENTITY,
        Rect::new(0.0, 0.0, 1.0, 1.0),
        &cache,
        pdf.xref(),
        settings,
    );

    // Run everything!
    let page = &pdf.pages()[0];
    interpret_page(page, &mut context, &mut extractor);

    // Then just save all of the images!
    for (idx, img) in extractor.0.iter().enumerate() {
        img.save(format!("image_{idx}.png")).unwrap();
    }
}

struct ImageExtractor(Vec<DynamicImage>);

impl ImageExtractor {
    fn new() -> Self {
        Self(Vec::new())
    }
}

/// Implement `Device` for `ImageExtractor`. We can ignore most operations and only
/// need to implement `draw_rgba_image` and `draw_stencil_image`.
impl Device<'_> for ImageExtractor {
    fn set_soft_mask(&mut self, _: Option<SoftMask<'_>>) {}

    fn draw_path(&mut self, _: &BezPath, _: Affine, _: &Paint<'_>, _: &PathDrawMode) {}

    fn push_clip_path(&mut self, _: &ClipPath) {}

    fn push_transparency_group(&mut self, _: f32, _: Option<SoftMask<'_>>, _: BlendMode) {}

    fn draw_glyph(
        &mut self,
        _: &Glyph<'_>,
        _: Affine,
        _: Affine,
        _: &Paint<'_>,
        _: &GlyphDrawMode,
    ) {
    }

    fn pop_clip_path(&mut self) {}

    fn pop_transparency_group(&mut self) {}

    fn draw_image(&mut self, image: Image<'_, '_>, _: Affine) {
        match image {
            Image::Stencil(s) => {
                s.with_stencil(
                    |stencil, _paint| {
                        // Stencil images are gray-channel images that should be painted using the color stored in
                        // `paint`. For simplicity, we just store them as gray-channel for now.
                        self.0.push(DynamicImage::ImageLuma8(
                            ImageBuffer::from_raw(
                                stencil.width,
                                stencil.height,
                                stencil.data.clone(),
                            )
                            .unwrap(),
                        ));
                    },
                    None,
                );
            }
            Image::Raster(r) => {
                // The alpha and RGB channels are provided separately.
                r.with_rgba(
                    |image, alpha| {
                        let (rgb_data, width, height) = match image {
                            ImageData::Rgb(rgb) => (rgb.data, rgb.width, rgb.height),
                            ImageData::Luma(luma) => {
                                let rgb = luma
                                    .data
                                    .iter()
                                    .flat_map(|g| [*g, *g, *g])
                                    .collect::<Vec<_>>();
                                (rgb, luma.width, luma.height)
                            }
                        };

                        let image = if let Some(alpha) = alpha {
                            // This is not complete, as it can in theory happen that the alpha channel has a different
                            // dimension than the RGB channel. We ignore this edge case for this example.
                            if alpha.width == width && alpha.height == height {
                                let interleaved = rgb_data
                                    .chunks(3)
                                    .zip(alpha.data)
                                    .flat_map(|(rgb, a)| [rgb[0], rgb[1], rgb[2], a])
                                    .collect::<Vec<u8>>();

                                DynamicImage::ImageRgba8(
                                    ImageBuffer::from_raw(width, height, interleaved).unwrap(),
                                )
                            } else {
                                DynamicImage::ImageRgb8(
                                    ImageBuffer::from_raw(width, height, rgb_data).unwrap(),
                                )
                            }
                        } else {
                            DynamicImage::ImageRgb8(
                                ImageBuffer::from_raw(width, height, rgb_data).unwrap(),
                            )
                        };

                        self.0.push(image);
                    },
                    None,
                );
            }
        }
    }

    fn set_blend_mode(&mut self, _: BlendMode) {}
}