Java BufferedImage getRGB method and Color class

Question

What do the x and y parameters in the getRGB(x, y) method represent? What does the numerical return value represent?

How do I identify the color of specific pixels within a BufferedImage that is displayed on a DrawingPanel? Ideally I'd like to 'find' a word within an image, and underline or outline this word to create a relevant hyperlink. How can I translate these numerical values into human understandable colors like 'red' 'green' or 'blue'?

Yes, I understand that in the Color class an alpha value of 0-255 represents transparent to opaque. But what does this imply for the actual color? I'm happy to clarify if this doesn't make sense. Thank you for reading.

Answer 1

The x and y coordinates represent the pixel location, x going from left to right and y going from top to bottom (both starting at 0). So (0, 0) is the upper left pixel, and (width-1, height-1) is the bottom right pixel.

The integer value returned has the R, G, B and (potentially) Alpha values packed into a single int. Remember that an int contains 32 bits, so 8 of those bits are allocated to each of the values.

But, if you're not to good with shifting bits around inside an integer, the easiest thing to do is pass the integer value to the constructor of Color:

int rgba = image.getRGB(coordinates);
Color col = new Color(rgba, true);
int r = col.getRed();
int g = col.getGreen();
...

Obviously, recognising where a word is from raw pixel values is a whole nother, quite complex, problem.