protected boolean saveTGA(OutputStream output) {
    byte header[] = new byte[18];

     if (format == ALPHA) {  // save ALPHA images as 8bit grayscale
       header[2] = 0x0B;
       header[16] = 0x08;
       header[17] = 0x28;

     } else if (format == RGB) {
       header[2] = 0x0A;
       header[16] = 24;
       header[17] = 0x20;

     } else if (format == ARGB) {
       header[2] = 0x0A;
       header[16] = 32;
       header[17] = 0x28;

     } else {
       throw new RuntimeException("Image format not recognized inside save()");
     }
     // set image dimensions lo-hi byte order
     header[12] = (byte) (width & 0xff);
     header[13] = (byte) (width >> 8);
     header[14] = (byte) (height & 0xff);
     header[15] = (byte) (height >> 8);

     try {
       output.write(header);

       int maxLen = height * width;
       int index = 0;
       int col; //, prevCol;
       int[] currChunk = new int[128];

       // 8bit image exporter is in separate loop
       // to avoid excessive conditionals...
       if (format == ALPHA) {
         while (index < maxLen) {
           boolean isRLE = false;
           int rle = 1;
           currChunk[0] = col = pixels[index] & 0xff;
           while (index + rle < maxLen) {
             if (col != (pixels[index + rle]&0xff) || rle == 128) {
               isRLE = (rle > 1);
               break;
             }
             rle++;
           }
           if (isRLE) {
             output.write(0x80 | (rle - 1));
             output.write(col);

           } else {
             rle = 1;
             while (index + rle < maxLen) {
               int cscan = pixels[index + rle] & 0xff;
               if ((col != cscan && rle < 128) || rle < 3) {
                 currChunk[rle] = col = cscan;
               } else {
                 if (col == cscan) rle -= 2;
                 break;
               }
               rle++;
             }
             output.write(rle - 1);
             for (int i = 0; i < rle; i++) output.write(currChunk[i]);
           }
           index += rle;
         }
       } else {  // export 24/32 bit TARGA
         while (index < maxLen) {
           boolean isRLE = false;
           currChunk[0] = col = pixels[index];
           int rle = 1;
           // try to find repeating bytes (min. len = 2 pixels)
           // maximum chunk size is 128 pixels
           while (index + rle < maxLen) {
             if (col != pixels[index + rle] || rle == 128) {
               isRLE = (rle > 1); // set flag for RLE chunk
               break;
             }
             rle++;
           }
           if (isRLE) {
             output.write(128 | (rle - 1));
             output.write(col & 0xff);
             output.write(col >> 8 & 0xff);
             output.write(col >> 16 & 0xff);
             if (format == ARGB) output.write(col >>> 24 & 0xff);

           } else {  // not RLE
             rle = 1;
             while (index + rle < maxLen) {
               if ((col != pixels[index + rle] && rle < 128) || rle < 3) {
                 currChunk[rle] = col = pixels[index + rle];
               } else {
                 // check if the exit condition was the start of
                 // a repeating colour
                 if (col == pixels[index + rle]) rle -= 2;
                 break;
               }
               rle++;
             }
             // write uncompressed chunk
             output.write(rle - 1);
             if (format == ARGB) {
               for (int i = 0; i < rle; i++) {
                 col = currChunk[i];
                 output.write(col & 0xff);
                 output.write(col >> 8 & 0xff);
                 output.write(col >> 16 & 0xff);
                 output.write(col >>> 24 & 0xff);
               }
             } else {
               for (int i = 0; i < rle; i++) {
                 col = currChunk[i];
                 output.write(col & 0xff);
                 output.write(col >> 8 & 0xff);
                 output.write(col >> 16 & 0xff);
               }
             }
           }
           index += rle;
         }
       }
       output.flush();
       return true;

     } catch (IOException e) {
       e.printStackTrace();
       return false;
     }
  }