/*
 * File: GrayImage.java
 * --------------------
 * Creates grayscale version of an image.
 */

import acm.program.*;
import acm.graphics.*;

public class GrayImage extends GraphicsProgram {

	public void run() {
		GImage image = new GImage("Claire.JPG");
		GImage grayImage = createGrayscaleImage(image);

		add(image, 0, 50);
		add(grayImage, 380, 50);
	}


	/* Creates a grayscale version of the original image */
	private GImage createGrayscaleImage(GImage image) {
		// Gets copy of pixel array from image
		int[][] array = image.getPixelArray();

		int height = array.length;    // number of rows in grid
		int width = array[0].length;  // number of columns in a row

		for (int i = 0; i < height; i++) {
			for (int j = 0; j < width; j++) {
				int pixel = array[i][j];
				
				int r = GImage.getRed(pixel);
				int g = GImage.getGreen(pixel);
				int b = GImage.getBlue(pixel);
				
				int xx = computeLuminosity(r, g, b);
				
				array[i][j] = GImage.createRGBPixel(xx, xx, xx);
			}
		}
		return new GImage(array);
	}

	/* Calculates the luminosity of a pixel using NTSC formula */
	private int computeLuminosity(int r, int g, int b) {
		return GMath.round((0.299 * r) + (0.587 * g) + (0.114 * b));
	}

}