import java.awt.image.BufferedImage;
import java.io.File;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.file.Files;
import javax.imageio.ImageIO;
/** Render a 160x120 payload (NUC block) with a straight linear map, to see whether
 *  structure in the final JPEG is in the DATA or added by the display stage. */
public class NucDump {
    public static void main(String[] a) throws Exception {
        byte[] b = Files.readAllBytes(new File(a[0]).toPath());
        ByteBuffer bb = ByteBuffer.wrap(b).order(ByteOrder.LITTLE_ENDIAN);
        int t = b.length - 152, ddt = bb.getInt(t + 4), bodySize = bb.getInt(ddt + 4);
        int p = ddt + 0x88, end = p + bodySize, off = -1;
        while (p + 8 <= end) {
            int m = bb.getInt(p), len = bb.getInt(p + 4);
            if (len < 0 || p + 8 + len > end) break;
            if (m == 0x5BB5B560 && len >= 38400) { off = p + 8; break; }
            p += 8 + len;
        }
        if (off < 0) { System.out.println("no NUC block"); return; }
        int W = 160, H = 120;
        int[] v = new int[W * H];
        for (int i = 0; i < W * H; i++) v[i] = (b[off + 2 * i] & 0xFF) | ((b[off + 2 * i + 1] & 0xFF) << 8);
        int lo = Integer.MAX_VALUE, hi = Integer.MIN_VALUE;
        for (int x : v) { if (x < lo) lo = x; if (x > hi) hi = x; }
        BufferedImage im = new BufferedImage(W, H, BufferedImage.TYPE_INT_RGB);
        for (int y = 0; y < H; y++)
            for (int x = 0; x < W; x++) {
                int g = (int) Math.round(255.0 * (v[y * W + x] - lo) / Math.max(1, hi - lo));
                im.setRGB(x, y, (g << 16) | (g << 8) | g);
            }
        ImageIO.write(im, "png", new File(a[1]));
        System.out.println("wrote " + a[1] + "  range " + lo + ".." + hi);
    }
}