Process Image File in Java: Read RGB Info from Bitmap

[BicycleTree]

I want to write a program in Java that reads RGB information pixel-by-pixel from an image file, processes that information, and then writes it to a text file. I know how to do everything except read from the image file. I'm thinking a Bitmap file might be the best choice for the image file, unless there's a simpler option.

I am not averse to using a "kludge" like transforming the image file into text using some other application and then working with that, if that would make the processing easier; I only care about the result. I have read that it is easy to do a text dump of a bitmap like that in Unix, but I'm using Windows XP. So, how does one work with image files? Thanks for any help.

 

[robphy]

Try ImageJ
http://rsb.info.nih.gov/ij/
and check out the plugins
http://rsb.info.nih.gov/ij/plugins/index.html

You can also browse the source
http://rsb.info.nih.gov/ij/docs/source/index.html

 

[BicycleTree]

How do I use all this stuff? I can't tell if that's what I want or not. It seems that it was designed as a stand-alone program.

All I want to do is read RGB triplets from a bitmap file.

 

[so-crates]

Sun has there own API for accessing and manipulating images It is called the Java Advanced Imaging toolkit (JAI). Documentation can be found here

An alternative would be to write your own methods to read in the header and map the file to some custom class(I would call it BMPmage or something like that) and perform you processing from there. BMP iis a pretty simple format, unlike say JPEG or even GIF that has compression. Here is a URL I found that documents the BMP format http://www.inversereality.org/tutorials/graphics%20programming/BitmapLoading.html
You should be able to google for more.

ImageJ's functionality doesn't seem easier to use than Sun's JAI, so I wouldn't see much point in using it. If you did go that route, it looks like you would download the source code for the application and use the classes to load your image file into an ImagePlus class, to perform manipulation on them. Browsing the source however, the API does not seem like it was that well designed (classes are too interdependent and not self-contained like they should be)

 

[oldtobor]

Try using perl from the XP DOS command line. If you don't know it, read something about some of the instructions, these problems are nicely dealt with in perl.

example:

$_='p0.jpg';
open inf,$_; binmode inf;

while (read(inf,$buffer,6))
{ # here you can do whatever with each character of the binary file


execute from dos as c:\perl thisprogram.pl > result

 

[chroot]

Java contains built-in image-processing functions.

Use java.awt.Toolkit.createImage() or java.awt.Toolkit.getImage() to read a GIF, JPG, or PNG file into a java.awt.Image object.

Next, use java.awt.image.PixelGrabber to read the pixel data from the Image.

Whatever you do, don't try to follow oldtobor's horrible advice and try to decode the image yourself, byte-by-byte. Image manipulation libraries exist for Perl, also.

- Warren

 

[so-crates]

Java contains built-in image-processing functions.

Use java.awt.Toolkit.createImage() or java.awt.Toolkit.getImage() to read a GIF, JPG, or PNG file into a java.awt.Image object.

Next, use java.awt.image.PixelGrabber to read the pixel data from the Image.

It sounds like he needs access to BMP, which is not supported by the AWT methods.

Whatever you do, don't try to follow oldtobor's horrible advice and try to decode the image yourself, byte-by-byte. Image manipulation libraries exist for Perl, also.
- Warren

I don't see how reading and parsing an BMP is that bad. Its a pretty simple, uncompressed image format.

 

[so-crates]

Try using perl from the XP DOS command line. If you don't know it, read something about some of the instructions, these problems are nicely dealt with in perl.

example:

$_='p0.jpg';
open inf,$_; binmode inf;

while (read(inf,$buffer,6))
{ # here you can do whatever with each character of the binary file

execute from dos as c:\perl thisprogram.pl > result

He wants to do it in Java, not Perl.

 

[master_coda]

I think you can use javax.imageio.ImageIO.read to read BMP files.

 

[BicycleTree]

Coda, ImageIO might be the trick. Here is the line I'm going to try:
BufferedImage input = ImageIO.read(new File(INPUT));
And then I can use input to get RGB triplets (I hope).

 

[BicycleTree]

I don't know, I keep getting a null pointer exception. I'm not sure how I'm supposed to write the filename--my best guess right now is "c:\\javawork\\textpics\\input.bmp", is that right?

 

[BicycleTree]

Ah, it was just that it couldn't read a bmp file. It's working with a gif file.

 

[master_coda]

Ah, it was just that it couldn't read a bmp file. It's working with a gif file.

I know that it supports BMP files in the newest version of Java (1.5 or 5.0, whatever). It might not in the 1.4 version.

 

[BicycleTree]

Yeah, I have the 1.4.2 version. That image there was the output of the program when I just ran it (only a couple bugs). There still is a bug though because a line got chopped off the top of that. Hmm.

 

[BicycleTree]

Aha, it didn't get chopped off, it's just way over on the right.

 

[BicycleTree]

This is strange... I just changed the input file for another one and now it's not working. Maybe variation in the file format?

 

[BicycleTree]

It works! Almost! Now that is one strange error, with the right side of his head getting chopped off and put on the next line. I don't know what's causing that...

 

[BicycleTree]

(The trick, by the way, I believe lies in first saving it as a 24 bit bitmap before saving it as a gif; I think that ensures that the gif is in the right format)

 

[BicycleTree]

NOW it's working! Thanks a lot everyone for your help. Now I can transform a smiley into a text image in a matter of seconds :). If you posted in this thread and you want to see the code so you can do it too then ask me; I don't want to just post it for everyone to see.