srecord noeq Hi15ImageStreaks(Hi15Image inputImage) {

  // pixel indices of streak ends

  new IntBuffer streakData;

  int[] lineStarts;

  gettable int w;

  run {

    var streakData = this.streakData;

    int w = this.w = inputImage.w(), h = inputImage.h();

    lineStarts = new int[h+1];

    short[] pixels = inputImage.pixels;

    int iPixel = 0;

    for y to h: {

      lineStarts[y] = streakData.size();

      int lineEnd = iPixel+w;

      while (iPixel < lineEnd) {

        short color = pixels[iPixel];

        do

          ++iPixel;

        while (iPixel < lineEnd && pixels[iPixel] == color);

        streakData.add(iPixel);

      }

    }

    lineStarts[l(lineStarts)-1] = streakData.size();

  }

  selfType runAndReturn() { run(); this; }

  int nStreaks() { ret streakData.size(); }

  int h() { ret lineStarts.length-1; }

  int lineEnd(int y) { ret lineStarts[y+1]; }

  L<Rect> streaksAsRects() {

    ret listFromFunction(nStreaks(), iStreak -> {

      int iPixel = iStreak == 0 ? 0 : streakData.get(iStreak-1);

      int jPixel = streakData.get(iStreak++);

      int w = w();

      ret rect(iPixel % w, iPixel/w, jPixel-iPixel, 1);

    });

  }

}