Program: 80056
Project: 80056
Buggy source:
@Override public Void call() throws Exception {
  BufferedImage in00=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2,tile.y * 2,state.imageFormat));
  BufferedImage in10=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2 + 1,tile.y * 2,state.imageFormat));
  BufferedImage in01=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2,tile.y * 2 + 1,state.imageFormat));
  BufferedImage in11=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2 + 1,tile.y * 2 + 1,state.imageFormat));
  if (in00 == null && in10 == null && in01 == null && in11 == null)   return null;
  Log.logDebug("String_Node_Str" + tile.x + "String_Node_Str"+ tile.y);
  final int pixelFormat=state.imageFormat.hasAlpha() ? BufferedImage.TYPE_4BYTE_ABGR : BufferedImage.TYPE_3BYTE_BGR;
  BufferedImage outImg=new BufferedImage(state.tileWidth,state.tileHeight,pixelFormat);
  Graphics2D g=(Graphics2D)outImg.getGraphics();
  g.setColor(state.backgroundColor);
  g.fillRect(0,0,state.tileWidth,state.tileHeight);
  g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,RenderingHints.VALUE_INTERPOLATION_BICUBIC);
  g.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_QUALITY);
  g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
  final int halfWidth=state.tileWidth / 2;
  final int halfHeight=state.tileHeight / 2;
  if (in00 != null)   g.drawImage(in00,0,0,halfWidth,halfHeight,null);
  if (in10 != null)   g.drawImage(in10,halfWidth,0,halfWidth,halfHeight,null);
  if (in01 != null)   g.drawImage(in01,0,halfHeight,halfWidth,halfHeight,null);
  if (in11 != null)   g.drawImage(in11,halfWidth,halfHeight,halfWidth,halfHeight,null);
  try {
    File outputFile=TileRenderer.getImageFile(state.outputDir,tile.x,tile.y,state.imageFormat);
    Screenshot.write(outputFile,outImg,state.imageFormat,state.imageCompressionLevel);
    changedFileList.writeLine(outputFile.getAbsolutePath());
  }
 catch (  Exception e) {
    e.printStackTrace();
  }
  return null;
}

Fixed version (ground truth):
@Override public Void call() throws Exception {
  BufferedImage in00=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2,tile.y * 2,state.imageFormat));
  BufferedImage in10=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2 + 1,tile.y * 2,state.imageFormat));
  BufferedImage in01=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2,tile.y * 2 + 1,state.imageFormat));
  BufferedImage in11=getTile(TileRenderer.getImageFile(state.inputDir,tile.x * 2 + 1,tile.y * 2 + 1,state.imageFormat));
  if (in00 == null && in10 == null && in01 == null && in11 == null)   return null;
  Log.logDebug("String_Node_Str" + tile.x + "String_Node_Str"+ tile.y);
  final boolean hasAlpha=state.imageFormat.hasAlpha();
  final int pixelFormat=hasAlpha ? BufferedImage.TYPE_4BYTE_ABGR : BufferedImage.TYPE_3BYTE_BGR;
  BufferedImage outImg=new BufferedImage(state.tileWidth,state.tileHeight,pixelFormat);
  Graphics2D g=(Graphics2D)outImg.getGraphics();
  if (!hasAlpha) {
    g.setColor(state.backgroundColor);
    g.fillRect(0,0,state.tileWidth,state.tileHeight);
  }
  g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,RenderingHints.VALUE_INTERPOLATION_BICUBIC);
  g.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_QUALITY);
  g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
  final int halfWidth=state.tileWidth / 2;
  final int halfHeight=state.tileHeight / 2;
  if (in00 != null)   g.drawImage(in00,0,0,halfWidth,halfHeight,null);
  if (in10 != null)   g.drawImage(in10,halfWidth,0,halfWidth,halfHeight,null);
  if (in01 != null)   g.drawImage(in01,0,halfHeight,halfWidth,halfHeight,null);
  if (in11 != null)   g.drawImage(in11,halfWidth,halfHeight,halfWidth,halfHeight,null);
  try {
    File outputFile=TileRenderer.getImageFile(state.outputDir,tile.x,tile.y,state.imageFormat);
    Screenshot.write(outputFile,outImg,state.imageFormat,state.imageCompressionLevel);
    changedFileList.writeLine(outputFile.getAbsolutePath());
  }
 catch (  Exception e) {
    e.printStackTrace();
  }
  return null;
}