Method imageioDPI

core/src/processing/awt/ShimAWT.java:643–678

(ImageWriter writer, ImageWriteParam param, double dpi)

  @SuppressWarnings("SameParameterValue")
  static private IIOMetadata imageioDPI(ImageWriter writer, ImageWriteParam param, double dpi) {
    // http://stackoverflow.com/questions/321736/how-to-set-dpi-information-in-an-image
    ImageTypeSpecifier typeSpecifier =
      ImageTypeSpecifier.createFromBufferedImageType(BufferedImage.TYPE_INT_RGB);
    IIOMetadata metadata =
      writer.getDefaultImageMetadata(typeSpecifier, param);

    if (!metadata.isReadOnly() && metadata.isStandardMetadataFormatSupported()) {
      // for PNG, it's dots per millimeter
      double dotsPerMilli = dpi / 25.4;

      IIOMetadataNode horiz = new IIOMetadataNode("HorizontalPixelSize");
      horiz.setAttribute("value", Double.toString(dotsPerMilli));

      IIOMetadataNode vert = new IIOMetadataNode("VerticalPixelSize");
      vert.setAttribute("value", Double.toString(dotsPerMilli));

      IIOMetadataNode dim = new IIOMetadataNode("Dimension");
      dim.appendChild(horiz);
      dim.appendChild(vert);

      IIOMetadataNode root = new IIOMetadataNode("javax_imageio_1.0");
      root.appendChild(dim);

      try {
        metadata.mergeTree("javax_imageio_1.0", root);
        return metadata;

      } catch (IIOInvalidTreeException e) {
        System.err.println("Could not set the DPI of the output image");
        e.printStackTrace();
      }
    }
    return null;
  }


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