DraggablePDFGraphicsContextViewer.java

import java.awt.Color;
import java.awt.geom.AffineTransform;

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.rendering.PDFRenderer;
import org.jfree.fx.FXGraphics2D;

import javafx.application.Application;
import javafx.scene.Cursor;
import javafx.scene.Scene;
import javafx.scene.canvas.Canvas;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;

public class DraggablePDFGraphicsContextViewer extends Application {

	public static void main(String[] args) {
		launch(args);
	}
	
	int pdfScale = 100;

	@Override
	public void start(Stage primaryStage) throws Exception {
		int width = 590;
		int height = 840;
		
		PDDocument doc = PDDocument.load(DraggablePDFGraphicsContextViewer.class.getResourceAsStream("sample.pdf"));
		Pane pane = new Pane();
		PdfCanvas canvas = new PdfCanvas(doc, 0, pdfScale);
		canvas.setWidth(width);
		canvas.setHeight(height);
		pane.getChildren().add(canvas);
		canvas.renderPdf();

		Scene scene = new Scene(pane, width, height);
		primaryStage.setTitle(getClass().getName());
		primaryStage.setScene(scene);
		primaryStage.show();
	}

	public static class PdfCanvas extends Canvas {
		PDFRenderer renderer;
		Canvas canvas;
		double dragStartMouseX;
		double dragStartMouseY;
		double pdfX;//PDF描画の起点（X座標）
		double pdfY;//PDF描画の起点（Y座標）
		int page;
		int pdfScale;

		public PdfCanvas(PDDocument doc, int page, int scale) {
			renderer = new PDFRenderer(doc);
			this.pdfScale = scale;
			this.page = page;
			//press時にマウス座標を取得
			setOnMousePressed(e -> {
				dragStartMouseX = e.getSceneX();
				dragStartMouseY = e.getSceneY();
				getScene().setCursor(Cursor.CLOSED_HAND);
			});
			//マウスリリース時に、移動した分だけPDFレンダリングの起点をずらす
			setOnMouseReleased(e -> {
				double offsetX = e.getSceneX() - dragStartMouseX;
				double offsetY = e.getSceneY() - dragStartMouseY;
				pdfX = pdfX + offsetX;
				pdfY = pdfY + offsetY;
				getScene().setCursor(Cursor.DEFAULT);
				renderPdf();
			});
		}

		public void renderPdf() {
			FXGraphics2D g2 = new FXGraphics2D(getGraphicsContext2D());
			g2.clearRect(0, 0, (int) getWidth(), (int) getHeight());
			//AffineTransformを使って、graphicsへの書き込みの起点をずらす
			AffineTransform savedAffineTrasform = g2.getTransform();
			g2.setTransform(AffineTransform.getTranslateInstance(pdfX, pdfY));
			try {
				renderer.renderPageToGraphics(page, g2, pdfScale);
			} catch (Exception e) {
				throw new RuntimeException(e);
			} finally {
				g2.setTransform(savedAffineTrasform);
			}
		}
	}
}