Question

I’m making an applet that lets users crop out a piece of an image and save it. For cropping, I’m going to implement a “magic wand”-esque tool. I can do all this in Matlab but i’m having some trouble figuring out the Java libraries. Here are a few tasks I need to perform:

• Randomly access pixels in an image by (x,y) and return a single object (java.awt.Color, ARGB int, short[], whatever — as long as I’m not dealing with channels individually)
• Create an alpha channel from a boolean[ ][ ]
• Create a N by M image that’s initialized to green

Any pros out there who can help me? Just some code snippets off the top of your head would be fine.

Many thanks,

Neal

Answer 1

You want to use the Java2D libraries. Specifically, you want to use the BufferedImage class from the library to deal with your images. You can access individual pixels and do all of the things you have specified above. Sun/Oracle has a good tutorial to get you started in the right direction. The second part in that tutorial goes over creating an alpha channel. Oh, and to access individual pixels, you want to use the WritableRaster class. So you can do something like this. Hope this gets you started.

WritableRaster imageRaster = Bufferedimg.getRaster();
//use java random generation to get a random x and y coordinate, then call this to access the pixel
imageRaster.getPixel(x, y,(int[])null);