package ie.dcu.segment.util;

import org.eclipse.swt.graphics.*;

/**
 * Converts an SWT ImageData object to a linear array of bytes. 
 * 
 * @author Kevin McGuinness
 */
public class ImageByteConverter {
	private final int npixels;
	private final int nsamples;
	private final int[] pixels;
	private final byte[] samples;
	
	/**
	 * Create an converter object for images of the given size.
	 * 
	 * @param width
	 *        The image width.
	 * @param height
	 *        The image height.
	 */
	public ImageByteConverter(int width, int height) {
		this.npixels = width*height;
		this.nsamples = npixels*3;
		this.pixels = new int[npixels];
		this.samples = new byte[nsamples];
	}
	
	/**
	 * Convert an SWT ImageData object to a linear array of bytes. The returned
	 * array contains three bytes per pixel, and is in row-major order. The
	 * bytes are ordered RGB.
	 * 
	 * @param data
	 *        An image data object.
	 * @param clone
	 *        If <code>false</code> returns a shared array, otherwise returns a
	 *        new array.
	 * @return A byte array of RGB values in row-major order.
	 */
	public byte[] convert(ImageData data, boolean clone) {
		PaletteData p = data.palette;
		
		data.getPixels(0, 0, npixels, pixels, 0);
		if (p.isDirect) {
			for (int i = 0, j = 0; i < npixels; i++) {
				// Unpack
				int r, g, b, pel = pixels[i];
				
				// red
				r = pel & p.redMask;
				r = (p.redShift < 0) ? 
						r >>> -p.redShift : r << p.redShift;
				
				// green
				g = pel & p.greenMask;
				g = (p.greenShift < 0) ? 
						g >>> -p.greenShift : g << p.greenShift;
				
				// blue
				b = pel & p.blueMask;
				b = (p.blueShift < 0) ? 
						b >>> -p.blueShift : b << p.blueShift;
				
				// assign
				samples[j++] = (byte) r;
				samples[j++] = (byte) g;
				samples[j++] = (byte) b;
			}
		} else {
			// Indirect palette
			for (int i = 0, j = 0; i < npixels; i++) {
				RGB color = p.colors[pixels[i]];
				samples[j++] = (byte) color.red;
				samples[j++] = (byte) color.green;
				samples[j++] = (byte) color.blue;
			}
		}
		
		if (clone) {
			return samples.clone();
		}
		
		return samples;
	}
	
	/**
	 * Convert an SWT image data object to a linear array of bytes. The returned
	 * array contains three bytes per pixel, and is in row-major order. The
	 * bytes are ordered RGB. 
	 * 
	 * @param data
	 *        An image data object.
	 * @return A byte array of RGB values in row-major order.
	 */
	public static byte[] convert(ImageData data) {
		return new ImageByteConverter(data.width, data.height).convert(data, false);
	}
}