将缩放图像等级保存到文件

Question

假设我想加载一个shp文件，在它上面做我的东西并将地图保存为图像。

为了保存图像我使用：

public void saveImage(final MapContent map, final String file, final int imageWidth) { 

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

     Rectangle imageBounds = null; 
     ReferencedEnvelope mapBounds = null; 

     try { 
      mapBounds = map.getMaxBounds(); 
      double heightToWidth = mapBounds.getSpan(1)/mapBounds.getSpan(0); 
      imageBounds = new Rectangle(0, 0, imageWidth, (int) Math.round(imageWidth * heightToWidth)); 
     } catch (Exception e) { 
      // Failed to access map layers 
      throw new RuntimeException(e); 
     } 

     BufferedImage image = new BufferedImage(imageBounds.width, imageBounds.height, BufferedImage.TYPE_INT_RGB); 
     Graphics2D gr = image.createGraphics(); 
     gr.setPaint(Color.WHITE); 
     gr.fill(imageBounds); 

     try { 
      renderer.paint(gr, imageBounds, mapBounds); 
      File fileToSave = new File(file); 
      ImageIO.write(image, "png", fileToSave); 
     } catch (IOException e) { 
      throw new RuntimeException(e); 
     } 
    } 

但是，让我们说我在做这样的事情：

... 
MapContent map = new MapContent(); 
map.setTitle("TEST"); 
map.addLayer(layer); 
map.addLayer(shpLayer); 

// zoom into the line 
MapViewport viewport = new MapViewport(featureCollection.getBounds()); 
map.setViewport(viewport); 

saveImage(map, "/tmp/img.png", 800); 

1）的问题是缩放级别ISN”保存在图像文件上。是否有一种方法可以保存它？

2）当我在做MapViewport(featureCollection.getBounds());有没有办法扩大一点点的边界，以获得更好的视觉表现？

...

Answer 1

，你是不是保存地图，在当前缩放级别的原因是，在你的saveImage方法，你也行：

mapBounds = map.getMaxBounds(); 

它一直使用的充分程度地图上，你可以将其更改为

mapBounds = map.getViewport().getBounds(); 

您可以通过类似扩展边界框：

ReferencedEnvelope bounds = featureCollection.getBounds(); 
    double delta = bounds.getWidth()/20.0; //5% on each side 
    bounds.expandBy(delta); 
    MapViewport viewport = new MapViewport(bounds); 
    map.setViewport(viewport); 

一个更快的（更容易）的方式来保存地图从GUI是使用方法像这里面只是保存究竟是什么在屏幕上：

public void drawMapToImage(File outputFile, String outputType, 
     JMapPane mapPane) { 
    ImageOutputStream outputImageFile = null; 
    FileOutputStream fileOutputStream = null; 
    try { 
     fileOutputStream = new FileOutputStream(outputFile); 
     outputImageFile = ImageIO.createImageOutputStream(fileOutputStream); 
     RenderedImage bufferedImage = mapPane.getBaseImage(); 
     ImageIO.write(bufferedImage, outputType, outputImageFile); 
    } catch (IOException ex) { 
     ex.printStackTrace(); 
    } finally { 
     try { 
      if (outputImageFile != null) { 
       outputImageFile.flush(); 
       outputImageFile.close(); 
       fileOutputStream.flush(); 
       fileOutputStream.close(); 
      } 
     } catch (IOException e) {// don't care now 
     } 
    } 
}