Re: is that possible to include a small PNG file as part of Java class?

From:
Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups:
comp.lang.java.programmer
Date:
Sun, 29 Jun 2014 08:15:50 -0400
Message-ID:
<lop01n$7k6$1@dont-email.me>
On 6/29/2014 5:14 AM, Wanja Gayk wrote:

In article <lo9mla$gkm$1@dont-email.me>, Eric Sosman (esosman@comcast-
dot-net.invalid) says...

On 6/23/2014 12:02 PM, www wrote:

Hi:

I have a simple Java class: Abc.java. The method within it needs to access a small PNG file(it's an icon picture). Right now, this picture file("abc.png") is located at nonsrc/icons/abc.png

So this class is a bit pain. Abc.class won't work in the absence of abc.png. When I create an executable JAR, this is pain: always need to remember to include abc.png file inside it.

I am wondering if there is a way that I can "convert" abc.png into some sort of Java code and I can put it in Abc.java. So Abc.class alone can perform the job, without the need of presence of abc.png. Is that possible?

Hope I have explained my intention well.


      Martin Gregorie's response seems to be good advice. However, if
you simply *must* incorporate your PNG image as a class, you could do
so with a big byte[] array:

    private static final byte[] PNG_BUFFER = {
        (byte)0x89, 0x50, 0x4E, 0x47, ... };

    public static Image getMyPNG() {
        return ImageIO.read(new ByteArrayInputStream(PNG_BUFFER));
    }

However, this approach will only work for fairly small images. The
problem is that Java class files have no way to store an initialized
array: The byte[] array above actually compiles to the equivalent of

    private static final byte[] PNG_BUFFER = new byte[whatever];
    static {
        PNG_BUFFER[0] = (byte)0x89;
        PNG_BUFFER[1] = 0x50;
        PNG_BUFFER[2] = 0x4E;
        PNG_BUFFER[3] = 0x47;
        ...
    }

... with about four or so bytecode instructions per array element.


Just wondering: why not use a string?

private static final String imageAsBase64
   = "SOME_BASE64_STRING_GOES_HERE";

public static Image getMyPNG() {
  return ImageIO.read(
   new ByteArrayInputStream(
    SomeUtil.base64ToBytes(imageAsBase64)));
}

Of course Base64 is notoriously inefficient (there's still Base85
though), but he's talking about "small PNG files", not large ones.
[...]


     I'd thought about using something like

    private static final String PNG_BUFFER =
        "\u8950\u4E47...";

.... which could then be unpacked at run time into a byte[] of twice
as many elements and used as before. But that seemed so foully ugly
that I had to suppress the urge to vomit, so I didn't mention it.

     Base64 simply didn't occur to me, and when I saw it mentioned
by others I said "Duh!" and delivered a self-administered dope slap.

--
Eric Sosman
esosman@comcast-dot-net.invalid

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