Working with DrJava - How can I load and alter a jpeg?

Question

I'm a complete beginner to programming and I've been trying to figure this out for a while but I'm lost. There's a few different versions of the question, but I think I can figure the rest out after I have one finished code, so I'm just going explain the one. The first part asks to write a program using DrJava that will display an image, wait for a user response, and then reduce the image to have only 4 levels per color channel. It goes on to say this:

"What we want to do is reduce each color channel from the range 0-255 (8 bits) to the range 0-3 (2 bits). We can do this by dividing the color channel value by 64. However, since our actual display still uses 1 byte per color channel, a values 0-3 will all look very much like black (very low color intensity). To make it look right, we need to scale the values back up to the original range (multiply by 64). Note that, if integer division is used, this means that only 4 color channel values will occur: 0, 64, 128 and 192, imitating a 2-bit color palate."

I don't even get where I'm supposed to put the picture and get it to load from. Basically I need it explained like I'm five. Thanks in advance!

Answer 1

Java API documentation will be your best resource.

You can read an BufferedImage via a function ImageIO.read(File).

BufferedImage is an Image, so you can display it a part of a JLabel or JButton.

BufferedImage can be created with different ColorModels, RGB, BGR, ARGB, one byte per colour, indexed colours and so on. Here you want to copy one BufferedImage to another with another Colormodel.

Basically you can create a new BufferedImage with the differing ColorModel, call:

Graphics g = otherImg.getGraphics();
g.drawImage(originalImg, ...);
ImageIO.write(otherImg, ...);