Geotools OSM Tile层无法加载图像，无法创建ImageInputStream

Question

我正在尝试使用 geotools 和切片客户端在给定的边界框中打印 OSM 切片，我已经实现了一个 wms 服务，可以读取 wms 请求并在给定的边界框中渲染图像，OSM 层是用作基础层，我还有其他层是矢量图层，我可以稍后添加，矢量图层在给定的边界框中正确显示，但不显示 osm 切片，用于向 osm 服务器发送请求的 URL 不'没有得到任何回应？我有以下错误：

2020-05-27 16:03:00.291 ERROR 26094 --- [pool-6-thread-1] org.geotools.tile                        : Failed to load image: https://tile.openstreetmap.org/8/123/106.png

java.io.IOException: Can't create an ImageInputStream!
    at org.geotools.image.io.ImageIOExt.read(ImageIOExt.java:339) ~[gt-coverage-22.2.jar:na]
    at org.geotools.image.io.ImageIOExt.readBufferedImage(ImageIOExt.java:402) ~[gt-coverage-22.2.jar:na]
    at org.geotools.tile.Tile.loadImageTileImage(Tile.java:175) ~[gt-tile-client-22.2.jar:na]
    at org.geotools.tile.Tile.getBufferedImage(Tile.java:163) ~[gt-tile-client-22.2.jar:na]
    at org.geotools.tile.util.TileLayer.getTileImage(TileLayer.java:143) [gt-tile-client-22.2.jar:na]
    at org.geotools.tile.util.TileLayer.renderTile(TileLayer.java:131) [gt-tile-client-22.2.jar:na]
    at org.geotools.tile.util.TileLayer.renderTiles(TileLayer.java:125) [gt-tile-client-22.2.jar:na]
    at org.geotools.tile.util.TileLayer.draw(TileLayer.java:86) [gt-tile-client-22.2.jar:na]
    at org.geotools.renderer.lite.CompositingGroup$WrappingDirectLayer.draw(CompositingGroup.java:228) [gt-render-22.2.jar:na]
    at org.geotools.renderer.lite.StreamingRenderer$RenderDirectLayerRequest.execute(StreamingRenderer.java:3850) [gt-render-22.2.jar:na]
    at org.geotools.renderer.lite.StreamingRenderer$PainterThread.run(StreamingRenderer.java:3911) [gt-render-22.2.jar:na]
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_232]
    at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_232]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_232]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_232]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_232]

对于源代码，这些是我添加 osm 平铺层的方式：

MapContent mapContent = new MapContent();
String baseURL = "https://tile.openstreetmap.org/";
TileService service = new OSMService("OSM", baseURL);
mapContent.addLayer(new TileLayer(service));

稍后我使用 gt-render 打印它：

StreamingRenderer renderer = new StreamingRenderer();
renderer.setMapContent(map);
ReferencedEnvelope mapBounds = mapRequest.getReferencedEnvelope();
Rectangle imageBounds = new Rectangle(0, 0, mapRequest.getWidth(), mapRequest.getHeight());

map.getViewport().setScreenArea(imageBounds);
map.getViewport().setBounds( mapBounds );

BufferedImage image = new BufferedImage(mapRequest.getWidth(), mapRequest.getHeight(),BufferedImage.TYPE_4BYTE_ABGR);
Graphics2D gr = image.createGraphics();

gr.setRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON));

int threads = Runtime.getRuntime().availableProcessors();
ExecutorService fixedPool = Executors.newFixedThreadPool(threads - 1);
        renderer.setThreadPool(fixedPool);

try {
        renderer.paint(gr, imageBounds, mapBounds);
        ImageIO.write(image, imageExtension, os);
    } 
catch (IOException e) {
            throw new RuntimeException(e);
    }

gr.dispose();
map.dispose();

我有一个硬编码版本的源代码来测试它：

  public void test(OutputStream os) throws NoSuchAuthorityCodeException, FactoryException {

        MapContent map = new MapContent();

        String baseURL = "https://tile.openstreetmap.org/";
        TileService service = new OSMService("OSM", baseURL);
        map.addLayer(new TileLayer(service));

        StreamingRenderer renderer = new StreamingRenderer();
        renderer.setMapContent(map);

        CoordinateReferenceSystem crs = CRS.decode("EPSG:3857");

        ReferencedEnvelope mapBounds = new ReferencedEnvelope(-939258.203568246,-626172.1357121639,3130860.67856082,3443946.746416902,crs);
        Rectangle imageBounds = new Rectangle(0, 0, 256, 256);

        map.getViewport().setScreenArea(imageBounds);
        map.getViewport().setBounds( mapBounds );

        BufferedImage image = new BufferedImage(256, 256,
                BufferedImage.TYPE_4BYTE_ABGR);
        Graphics2D gr = image.createGraphics();

        gr.setRenderingHints(new RenderingHints(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON));

        try {
            renderer.paint(gr, imageBounds, mapBounds);
            ImageIO.write(image, imageExtension, os);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }

        gr.dispose();
        map.dispose();
    }

Answer 1

问题似乎是，如果您不设置valid User-Agent header in your requests，OpenStreetMap 将返回 HTTP-429 错误（请求过多）。

我假设这是自上次使用或测试 OSM 磁贴代码以来的新要求。尽管在查看测试时，它可能实际上并没有获取要渲染的图块。

我在issue tracker 有raised a bug against gt-tile-client，我有一个PR to fix the issue，可以像WMTSTile implementation 一样添加标题。

它应该在今天晚些时候 2020 年 5 月 30 日的夜间主版本中可用。