// screenshot tool for "ZTE FTV Blade"  (6/23/2013)
// - grabs framebuffer /dev/graphics/fb0 (needs "chmod o+r")
// - converts each of the 800x480 pixels from rgb565le to rgb888 format
// - rotates 180° (frambuffer-->image)
// - for use in "Terminal IDE" (or Linux, copy raw data to "/dev/graphics/fb0")
// https://play.google.com/store/apps/details?id=com.spartacusrex.spartacuside
//
import java.io.*;

public class screenshot {

  // specific to "ZTE FTV Blade", adjust to your needs
  private static final int height = 800;
  private static final int width  = 480;
  private static final int pixlen = 2;
  private static final int frames = 2;
  // not sure what 2nd frame is, most times just black

  public static void main(String[] args) throws Exception {

    if (args.length != 0) {
      System.err.println("Usage:  java screenshot");
      System.exit(1);
    }

    // framebuffer
    String fb0 = "/dev/graphics/fb0";

    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    FileInputStream fin = new FileInputStream(fb0);
    copy(fin, bout);
    fin.close();
    byte b[] = bout.toByteArray();

    if (b.length != height*width*pixlen*frames) {
      System.err.println("incorrect framebuffer length "+b.length+" read");
      System.exit(1);
    }


    // allocate memory for rgb888 output
    byte B[] = new byte[height*width*3];

    // rotate 180 and convert
    for(int i=height*width*pixlen, j=0; i>0; i-=pixlen)
    {
      // this is specific to rgb565le with pixlen=2, adjust to your needs
      int s = ( (b[i-1]<0) ? 256+b[i-1] : b[i-1]) * 256
            + ( (b[i-2]<0) ? 256+b[i-2] : b[i-2]);

      // "white" should be "white", fill up with 1-bits at end
      // (0x07,0x03,0x07) is good enough as "black"
      B[j++] = (byte) ( ((s >> 8) & 0xF8) | 0x07 );
      B[j++] = (byte) ( ((s >> 3) & 0xFC) | 0x03 );
      B[j++] = (byte) ( ((s << 3) & 0xFF) | 0x07 );
    }

    ByteArrayInputStream bin = new ByteArrayInputStream(B);


    // Portable pixmap binary
    System.out.println("P6");

    System.out.println(width+" "+height);
    // rgb888
    System.out.println("255");

    copy(bin, System.out);
  }


  // copy method from From E.R. Harold's book "Java I/O"
  public static void copy(InputStream in, OutputStream out) 
    throws IOException {

    // do not allow other threads to read from the
    // input or write to the output while copying is
    // taking place

    synchronized (in) {
      synchronized (out) {

        byte[] buffer = new byte[256];
        while (true) {
          int bytesRead = in.read(buffer);
          if (bytesRead == -1) break;
          out.write(buffer, 0, bytesRead);
        }
      }
    }
  } 
}