obfuscate icons in j2me project - java-me

Question

I have created a j2me based project using Netbeans as an IDE. Now I want to obfuscate my resources of this project (icons ,images).so that the name or appearnace of images get changed .How can this be done?

Answer 1

You can change the image files name to not have an extension and be only one or two letters. Then change the code to use these new names instead of the original ones.
If your image files are PNGs you can change the PLTE chunk to wrong values during build and correct them during execution.
Image class does not have a method to easily change colors. A workaround could be to call getRGB method and iterate the rgbData array.
A better way is to read the file content, change the palette bytes and create an image from the resulting data. First lets create a helper method to read a whole InputStream and return a byte array with its content:
private byte [] readStream (InputStream in) throws IOException
{
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte [] buff = new byte [1024];
int size = in.read(buff);
while (size >= 0) {
baos.write(buff, 0, size);
size = in.read(buff);
}
return baos.toByteArray();
}
Next we have to find where is the palette chunk inside the byte array. Here is another helper method:
// return index where P of PLTE is found at buff array or -1
private int getPLTEIndex (byte [] buff) {
int i = -1;
// 4 == "PLTE".size()
if (buff != null && buff.length >= 4) {
boolean foundPalete = false;
boolean endOfBuff = false;
do {
i++;
foundPalete = buff[i] == 'P'
&& buff[i +1] == 'L'
&& buff[i +2] == 'T'
&& buff[i +3] == 'E';
endOfBuff = (i +4 >= buff.length);
} while (!foundPalete && !endOfBuff);
if (endOfBuff) {
i = -1;
}
}
return i;
}
And, finally, a method to change a color from the palette of PNG files with color type 3:
private byte [] setRGBColor (byte [] buff, int colorIndex, int colorNewValue) {
int i = getPLTEIndex(buff);
if (i >= 0) {
i += 4; // 4 == "PLTE".size()
i += (colorIndex * 3); // 3 == RGB bytes
if (i + 3 <= buff.length) {
buff[i] = (byte) (((colorNewValue & 0x00ff0000) >> 16) & 0xff);
buff[i +1] = (byte) (((colorNewValue & 0x0000ff00) >> 8) & 0xff);
buff[i +2] = (byte) ((colorNewValue & 0x000000ff) & 0xff);
}
}
return buff;
}
Below is a sample on how to use all the methods:
InputStream in = getClass().getResourceAsStream("/e");
try {
byte [] buff = readStream(in);
Image original = Image.createImage(buff, 0, buff.length);
buff = setRGBColor(buff, 0, 0x00ff0000); // set 1st color to red
buff = setRGBColor(buff, 1, 0x0000ff00); // set 2nd color to green
Image updated = Image.createImage(buff, 0, buff.length);
} catch (IOException ex) {
ex.printStackTrace();
}
As seen in http://smallandadaptive.blogspot.com.br/2010/08/manipulate-png-palette.html