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POPNG File format and Image bytes?
 

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    <p>I am currently trying to write a program to encode text into a png file only changing the least significant bit for each letter i want to encode in the picture, example I have a 'A' which is 65 and I use 8 different bytes to encode the letter A. So 01010100&lt;- 10101101&lt;- 11011010&lt;- 10101010&lt;- each of these I change the last bit and the put 10110110&lt;- 01010100&lt;- 01010100&lt;- 01010101&lt;- them together so 65 is 01000001 each number by the arrow is changed according to the 65.</p> <p>If I should approach this a different way suggestions would be awesome :). This is just a fun little project I wanted to do. But anyways back to my question.</p> <p>When I read in a image that is only 4 pixels big I get like 680 bytes which is crazy, or at least I think it is, maybe im wrong? 4 pixels with ARGB at 8 bits each should be 16 bytes with a few bytes im sure to tell the operating system that it is a png and how to handle it. So i was expecting maybe like 30 bytes. Maybe less. Am I looking at this the wrong way? When png images are compressed do they become bigger if it is a small picture? And also, when I was saving it back to the Hard drive I always got a larger file. The original picture was 8,554 kb and then it turned into like 16kb when I saved it back. Here is the code for getting the image bytes and for saving the image. Maybe I am doing something wrong or I am just not understanding it correctly.</p> <p>These are the ways I get the image (I tried 2 different things)</p> <blockquote> <p>// BufferedImage img = ImageIO.read(new File("image.png"));<br> BufferedImage img= robot.createScreenCapture(new Rectangle(1,2,2,2));</p> </blockquote> <p>how I saved two different ways again.</p> <blockquote> <p>try {<br> InputStream in = new ByteArrayInputStream(imgBytes); <br> BufferedImage bImageFromConvert = ImageIO.read(in); <br> ImageIO.write(bImageFromConvert, "png", new File( "image.png"));<br> <br> //FileOutputStream fos = new FileOutputStream("image.png");<br> //fos.write(b);<br> //fos.close();<br> }catch(Exception e){}<br></p> </blockquote> <p>How I got the bytes from the Image, again I tried two different ways, the second way that is commented out actually did give me the 16 bytes like I want but when I saved it the Windows couldnt Open it because it didnt know what it was i guess? Not sure, just said file not supported.</p> <blockquote> <p>byte[] imageBytes = null;<br> try{<br> ByteArrayOutputStream baos = new ByteArrayOutputStream();<br> ImageIO.write(image, "jpg", baos );<br> baos.flush();<br> imageBytes = baos.toByteArray();<br> baos.close();<br> }catch(IOException e){System.out.println(e.getMessage());}<br><br> // imageBytes = ((DataBufferByte) image.getData().getDataBuffer()).getData();<br> return imageBytes;<br></p> </blockquote> <p>Thanks!</p>
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