anchor.diff:      const initCodeSize = 8;
       output!.writeByte(initCodeSize);
   
  -    final hTab = Int32List(HSIZE);
  -    final codeTab = Int32List(HSIZE);
  +    final hTab = Int32List(_hsize);
  +    final codeTab = Int32List(_hsize);
       var remaining = width * height;
       var curPixel = 0;
   
  
positive.code: 
    OutputBuffer? output;
  
    static const GIF89_STAMP = 'GIF89a';
  
    static const IMAGE_DESC_RECORD_TYPE = 0x2c;
    static const EXTENSION_RECORD_TYPE = 0x21;
    static const TERMINATE_RECORD_TYPE = 0x3b;
  
    static const APPLICATION_EXT = 0xff;
    static const GRAPHIC_CONTROL_EXT = 0xf9;
  
    static const EOF = -1;
    static const BITS = 12;
    static const HSIZE = 5003; // 80% occupancy
    static const MASKS = [
      0x0000,
      0x0001,
      0x0003,
  
negative.code:   }
  
    void _writeGraphicsCtrlExt() {
      output!.writeByte(_extensionRecordType);
      output!.writeByte(_graphicControlExt);
      output!.writeByte(4); // data block size
  
      const transparency = 0;
  