From c3f78d95611d8cc5a885aef1d606698e539fd2bc Mon Sep 17 00:00:00 2001
From: Nico Weber <thakis@chromium.org>
Date: Tue, 11 Jul 2023 13:25:36 -0400
Subject: [PATCH] pdf: Add function to render a page of a PDF to a bitmap

Use like so:

    Build/lagom/bin/pdf --render foo.png --page=50 path/to.pdf
---
 Meta/Lagom/CMakeLists.txt         |  2 +-
 Userland/Utilities/CMakeLists.txt |  2 +-
 Userland/Utilities/pdf.cpp        | 56 +++++++++++++++++++++++++++++++
 3 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/Meta/Lagom/CMakeLists.txt b/Meta/Lagom/CMakeLists.txt
index e0de29926a..df3d88b386 100644
--- a/Meta/Lagom/CMakeLists.txt
+++ b/Meta/Lagom/CMakeLists.txt
@@ -561,7 +561,7 @@ if (BUILD_LAGOM)
         endif()
 
         add_executable(pdf ../../Userland/Utilities/pdf.cpp)
-        target_link_libraries(pdf LibCore LibPDF LibMain)
+        target_link_libraries(pdf LibCore LibGfx LibPDF LibMain)
 
         add_executable(sql ../../Userland/Utilities/sql.cpp)
         target_link_libraries(sql LibCore LibFileSystem LibIPC LibLine LibMain LibSQL)
diff --git a/Userland/Utilities/CMakeLists.txt b/Userland/Utilities/CMakeLists.txt
index bbfc94a9fa..6b0447f889 100644
--- a/Userland/Utilities/CMakeLists.txt
+++ b/Userland/Utilities/CMakeLists.txt
@@ -123,7 +123,7 @@ target_link_libraries(notify PRIVATE LibGfx LibGUI)
 target_link_libraries(open PRIVATE LibDesktop LibFileSystem)
 target_link_libraries(passwd PRIVATE LibCrypt)
 target_link_libraries(paste PRIVATE LibGUI)
-target_link_libraries(pdf PRIVATE LibPDF)
+target_link_libraries(pdf PRIVATE LibGfx LibPDF)
 target_link_libraries(pgrep PRIVATE LibRegex)
 target_link_libraries(pixelflut PRIVATE LibImageDecoderClient LibIPC LibGfx)
 target_link_libraries(pkill PRIVATE LibRegex)
diff --git a/Userland/Utilities/pdf.cpp b/Userland/Utilities/pdf.cpp
index 1a850b42c4..38b9bcb089 100644
--- a/Userland/Utilities/pdf.cpp
+++ b/Userland/Utilities/pdf.cpp
@@ -4,11 +4,14 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/LexicalPath.h>
 #include <LibCore/ArgsParser.h>
 #include <LibCore/File.h>
 #include <LibCore/MappedFile.h>
+#include <LibGfx/ImageFormats/PNGWriter.h>
 #include <LibPDF/CommonNames.h>
 #include <LibPDF/Document.h>
+#include <LibPDF/Renderer.h>
 
 static PDF::PDFErrorOr<void> print_document_info_dict(PDF::Document& document)
 {
@@ -41,6 +44,37 @@ static PDF::PDFErrorOr<void> print_document_info(PDF::Document& document)
     return {};
 }
 
+static PDF::PDFErrorOr<NonnullRefPtr<Gfx::Bitmap>> render_page(PDF::Document& document, int page_index)
+{
+    auto page = TRY(document.get_page(page_index));
+
+    auto page_size = Gfx::IntSize { 800, round_to<int>(800 * page.media_box.height() / page.media_box.width()) };
+
+    auto bitmap = TRY(Gfx::Bitmap::create(Gfx::BitmapFormat::BGRx8888, page_size));
+
+    auto errors = PDF::Renderer::render(document, page, bitmap, PDF::RenderingPreferences {});
+    if (errors.is_error()) {
+        for (auto const& error : errors.error().errors())
+            warnln("warning: {}", error.message());
+    }
+    return bitmap;
+}
+
+static PDF::PDFErrorOr<void> save_rendered_page(PDF::Document& document, int page_index, StringView out_path)
+{
+    auto bitmap = TRY(render_page(document, page_index));
+
+    if (!out_path.ends_with(".png"sv, CaseSensitivity::CaseInsensitive))
+        return Error::from_string_view("can only save to .png files"sv);
+
+    auto output_stream = TRY(Core::File::open(out_path, Core::File::OpenMode::Write));
+    auto buffered_stream = TRY(Core::OutputBufferedFile::create(move(output_stream)));
+    ByteBuffer bytes = TRY(Gfx::PNGWriter::encode(*bitmap));
+    TRY(buffered_stream->write_until_depleted(bytes));
+
+    return {};
+}
+
 static PDF::PDFErrorOr<int> pdf_main(Main::Arguments arguments)
 {
     Core::ArgsParser args_parser;
@@ -51,6 +85,12 @@ static PDF::PDFErrorOr<int> pdf_main(Main::Arguments arguments)
     StringView in_path;
     args_parser.add_positional_argument(in_path, "Path to input image file", "FILE");
 
+    StringView render_path;
+    args_parser.add_option(render_path, "Path to render a PDF page to", "render", {}, "PNG FILE");
+
+    u32 page_number = 1;
+    args_parser.add_option(page_number, "Page number (1-based)", "page", {}, "PAGE");
+
     args_parser.parse(arguments);
 
     auto file = TRY(Core::MappedFile::map(in_path));
@@ -70,6 +110,22 @@ static PDF::PDFErrorOr<int> pdf_main(Main::Arguments arguments)
 
     TRY(document->initialize());
 
+    if (page_number < 1 || page_number > document->get_page_count()) {
+        warnln("--page {} out of bounds, must be between 1 and {}", page_number, document->get_page_count());
+        return 1;
+    }
+
+    if (!render_path.is_empty()) {
+#if !defined(AK_OS_SERENITY)
+        // Get from Build/lagom/bin/pdf to Base/res/fonts.
+        auto source_root = LexicalPath(arguments.argv[0]).parent().parent().parent().parent().string();
+        Gfx::FontDatabase::set_default_fonts_lookup_path(DeprecatedString::formatted("{}/Base/res/fonts", source_root));
+#endif
+
+        TRY(save_rendered_page(document, page_number - 1, render_path));
+        return 0;
+    }
+
     TRY(print_document_info(*document));
 
     return 0;