Java 如何使用 Graphviz 从点文件格式生成 PNG 图像
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How to generate a PNG image from a dot file format with Graphviz
提问by
I have a java class that implements a priority queue. Then I have a class test that generates a graph like this:
我有一个实现优先级队列的 java 类。然后我有一个类测试，它生成一个这样的图表：
digraph G {
Milan (0.0) -> Turin (1.2)
Milan (0.0) -> Montreal (7.0)
Turin (1.2) -> Paris (5.8)
Turin (1.2) -> Tokyo (2.2)
}
This graph is saved in a file called "queue".
该图保存在名为“队列”的文件中。
Now I wish that this graph was displayed in a PNG image using Graphviz. So the last call of my test files (after you have created and filled the queue with priority) is:
现在我希望使用 Graphviz 将此图形显示在 PNG 图像中。所以我的测试文件的最后一次调用（在你创建并优先填充队列之后）是：
queue.toString("queue");
All right. The toString method is the following:
好的。toString 方法如下：
public void toString(String fileDot){
try {
FileOutputStream file = new FileOutputStream(fileDot);
PrintStream Output = new PrintStream(file);
Output.print(this.printQueue());
Output.close();
File f = new File(fileDot);
String arg1 = f.getAbsolutePath();
String arg2 = arg1 + ".png";
String[] c = {"dot", "-Tpng", arg1, "-o", arg2};
Process p = Runtime.getRuntime().exec(c);
int err = p.waitFor();
}
catch(IOException e1) {
System.out.println(e1);
}
catch(InterruptedException e2) {
System.out.println(e2);
}
}
private String printQueue() throws IOException {
String g = new String("");
char c = '"';
g = g.concat("digraph G {\n");
if(isEmpty())
g = g.concat(" " + "Empty priority queue.");
else {
for(int i = 0; i < lastIndex; i++) {
if(heap[2 * i] != null) {
g = g.concat("" + heap[i].elem + " (" + heap[i].prior + ") " + " " + " -> " + " " + "" + heap[i * 2].elem + " (" + heap[i * 2].prior + ") \n" );
if(heap[2 * i + 1] != null)
g = g.concat("" + heap[i].elem + " (" + heap[i].prior + ") " + " " + " -> " + " " + "" + heap[i * 2 + 1].elem + " (" + heap[i * 2 + 1].prior + ") \n" );
}
} //end for
} //end else
g = g.concat("}");
return g;
}
Why is not generated image .png? Where am I wrong? Of course I installed Graphviz. Thanks
为什么不是生成的图像 .png？我哪里错了？当然我安装了Graphviz。谢谢
采纳答案by Simon
When I ran the .dotfile above through dotat the command line, I got:
当我在命令行运行.dot上面的文件dot时，我得到：
$ dot -Tpng queue.dot -oqueue.png
Warning: queue.dot:2: syntax error in line 2 near '('
Thus, the parenthesised numbers in the node names are not valid in dotsyntax. If you remove them, I expect the .pngfile would be created successfully. If you need the parenthesised numbers in your output, I suggest looking up node labels in the GraphViz documentation.
因此，节点名称中带括号的数字在dot语法上无效。如果您删除它们，我希望该.png文件会成功创建。如果您需要输出中带括号的数字，我建议您在 GraphViz 文档中查找节点标签。
I'd also note that toString()does not seem like a particularly clear name for a function that creates a .pngfile so changing the name of the function might be advisable.
我还注意到，toString()对于创建.png文件的函数来说，这似乎不是一个特别清晰的名称，因此建议更改函数的名称。
回答by SSteve
Try using dot's -Ooption instead of -o. According to dot -?here's what it does:
尝试使用dot's-O选项而不是-o. 根据dot -?这里是它的作用：
- Automatically generate an output filename based on the input filename with a .'format' appended. (Causes all -ofile options to be ignored.)
- 根据输入文件名自动生成输出文件名并附加 .'format'。（导致所有 -ofile 选项被忽略。）
So you could change
所以你可以改变
String[] c = {"dot", "-Tpng", arg1, "-o", arg2};
to
到
String[] c = {"dot", "-Tpng", arg1, "-O"};
