Convert image from GeoJSON

Question

I am trying to convert feature collection GeoJSON into image. I want to use geotools to convert. I tested the soultion from this post here. But I am really noob that I ran into some errors like this:

Exception in thread "main" java.lang.IllegalArgumentException: Width (1000) and height (0) cannot be <= 0.

When I print the features.getBounds() it produces this result:

features ReferencedEnvelope[0.0 : -1.0, 0.0 : -1.0] Why is features.getBounds is not producing the correct result instead of 0? What should be the correct result?

This is the complete code:

    URL states = new URL("http://geojson.xyz/naturalearth-3.3.0/ne_110m_admin_1_states_provinces.geojson");
    FeatureJSON featureJSON = new FeatureJSON();
    FeatureCollection features = featureJSON.readFeatureCollection(states.openStream());
    MapContent mapContent = new MapContent();
    mapContent.setTitle("Quickstart");
    File outputFile = new File("states.png");
    ImageOutputStream outputImageFile = null;
    FileOutputStream fileOutputStream = null;
    try {
      fileOutputStream = new FileOutputStream(outputFile);
      outputImageFile = ImageIO.createImageOutputStream(fileOutputStream);
      int w = 1000;
      ReferencedEnvelope bounds = features.getBounds();
      int h = (int) (w * (bounds.getHeight() / bounds.getWidth()));
      BufferedImage bufferedImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
      Graphics2D g2d = bufferedImage.createGraphics();

      mapContent.getViewport().setMatchingAspectRatio(true);

      mapContent.getViewport().setScreenArea(new Rectangle(Math.round(w), Math.round(h)));
      mapContent.getViewport().setBounds(bounds);

      g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

      Rectangle outputArea = new Rectangle(w, h);

      GTRenderer renderer = new StreamingRenderer();
      LabelCacheImpl labelCache = new LabelCacheImpl();
      Map<Object, Object> hints = renderer.getRendererHints();
      if (hints == null) {
        hints = new HashMap<>();
      }
      hints.put(StreamingRenderer.LABEL_CACHE_KEY, labelCache);
      renderer.setRendererHints(hints);
      renderer.setMapContent(mapContent);
      renderer.paint(g2d, outputArea, bounds);
      ImageIO.write(bufferedImage, "png", outputImageFile);
    } catch (IOException ex) {
      ex.printStackTrace();
    } finally {
      try {
        if (outputImageFile != null) {
          outputImageFile.flush();
          outputImageFile.close();
          fileOutputStream.flush();
          fileOutputStream.close();
        }
      } catch (IOException e) {
          log.error("cannot produce image");
      }
    }
  }

Where am I getting this wrong? I just need to convert to get image. I would be happy if there is any other solution too. I need to use Java library so geotools is the best I found.

score 1 · Answer 1 · answered Jan 07 '20 at 13:59

1

If you would be able to use external tools, namely gdal, this could be done with

gdal_rasterize -burn 255 -burn 255 -burn 0 -ot Byte -of bmp -ts 1000 1000 my.geojson output.bmp

This would display everything in yellow on a black background.

...and then converting the bmp to png with your favorite tool, I would use imagemagick.

answered Jan 07 '20 at 13:59

til_b

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Hey @til_b Thank you for the answer. But i would like to clarify my needs.I have a REST API that response feature collection and front-end consume that API to load the features on google map. Somehow i would need to change feature collection response to image response. I cannot use external library . So as a first step i want to change Geojson file to image to response in REST API. I have little knowledge with how to do with images. – hotaru Jan 08 '20 at 07:10

Convert image from GeoJSON

1 Answers1