不用GD库生成当前时间的PNG格式图象的程序

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该程序是不用GD库可以生成当前时间的PNG格式图象，给人大开眼界，很有参考价值. teaman整理
   
  <?php
   
   function set_4pixel($r, $g, $b, $x, $y)
   {
   global $sx, $sy, $pixels;
   
   $ofs = 3 * ($sx * $y + $x);
   $pixels[$ofs] = chr($r);
   $pixels[$ofs + 1] = chr($g);
   $pixels[$ofs + 2] = chr($b);
   $pixels[$ofs + 3] = chr($r);
   $pixels[$ofs + 4] = chr($g);
   $pixels[$ofs + 5] = chr($b);
   $ofs += 3 * $sx;
   $pixels[$ofs] = chr($r);
   $pixels[$ofs + 1] = chr($g);
   $pixels[$ofs + 2] = chr($b);
   $pixels[$ofs + 3] = chr($r);
   $pixels[$ofs + 4] = chr($g);
   $pixels[$ofs + 5] = chr($b);
   }
   //生成数字图象的函数
   function draw2digits($x, $y, $number)
   {
   draw_digit($x, $y, (int) ($number / 10));
   draw_digit($x + 11, $y, $number % 10);
   }
   
   function draw_digit($x, $y, $digit)
   {
   global $sx, $sy, $pixels, $digits, $lines;
   
   $digit = $digits[$digit];
   $m = 8;
   for ($b = 1, $i = 0; $i < 7; $i++, $b *= 2) {
   if (($b & $digit) == $b) {
   $j = $i * 4;
   $x0 = $lines[$j] * $m + $x;
   $y0 = $lines[$j + 1] * $m + $y;
   $x1 = $lines[$j + 2] * $m + $x;
   $y1 = $lines[$j + 3] * $m + $y;
   if ($x0 == $x1) {
   $ofs = 3 * ($sx * $y0 + $x0);
   for ($h = $y0; $h <= $y1; $h++, $ofs += 3 * $sx) {
   $pixels[$ofs] = chr(0);
   $pixels[$ofs + 1] = chr(0);
   $pixels[$ofs + 2] = chr(0);
   }
   } else {
   $ofs = 3 * ($sx * $y0 + $x0);
   for ($w = $x0; $w <= $x1; $w++) {
   $pixels[$ofs++] = chr(0);
   $pixels[$ofs++] = chr(0);
   $pixels[$ofs++] = chr(0);
   }
   }
   }
   }
   }
   
   //将文字加入到图象中
   function add_chunk($type)
   {
   global $result, $data, $chunk, $crc_table;
   
   // chunk :为层
   // length: 4 字节: 用来计算 chunk
   // chunk type: 4 字节
   // chunk data: length bytes
   // CRC: 4 字节: 循环冗余码校验
   
   // copy data and create CRC checksum
   $len = strlen($data);
   $chunk = pack("c*", ($len >> 24) & 255,
   ($len >> 16) & 255,
   ($len >> 8) & 255,
   $len & 255);
   $chunk .= $type;
   $chunk .= $data;
   
   // calculate a CRC checksum with the bytes chunk[4..len-1]
   $z = 16777215;
   $z |= 255 << 24;
   $c = $z;
   for ($n = 4; $n < strlen($chunk); $n++) {
   $c8 = ($c >> 8) & 0xffffff;
   $c = $crc_table[($c ^ ord($chunk][$n])) & 0xff] ^ $c8;
   }
   $crc = $c ^ $z;
   
   $chunk .= chr(($crc >> 24) & 255);
   $chunk .= chr(($crc >> 16) & 255);
   $chunk .= chr(($crc >> 8) & 255);
   $chunk .= chr($crc & 255);
   
   // 将结果加到$result中
   $result .= $chunk;
   }
   
   
   //主程序
   
   $sx = 80;
   $sy = 21;
   $pixels = "";
   
   // 填充
   for ($h = 0; $h < $sy; $h++) {
   for ($w = 0; $w < $sx; $w++) {
   $r = 100 / $sx * $w + 155;
   $g = 100 / $sy * $h + 155;
   $b = 255 - (100 / ($sx + $sy) * ($w + $h));
   $pixels .= chr($r);
   $pixels .= chr($g);
   $pixels .= chr($b);
   }
   }
   
   $date = getdate();
   $s = $date["seconds"];
   $m = $date["minutes"];
   $h = $date["hours"];
   $digits = array(95, 5, 118, 117, 45, 121, 123, 69, 127, 125);
   $lines = array(1, 1, 1, 2, 0, 1, 0, 2, 1, 0, 1, 1, 0, 0, 0, 1, 0, 2, 1, 2, 0, 1, 1, 1, 0, 0, 1, 0);
   
   draw2digits(4, 2, $h);
   draw2digits(30, 2, $m);
   draw2digits(56, 2, $s);
   set_4pixel(0, 0, 0, 26, 7);
   set_4pixel(0, 0, 0, 26, 13);
   set_4pixel(0, 0, 0, 52, 7);
   set_4pixel(0, 0, 0, 52, 13);
   
   // 创建循环冗余码校验表
   $z = -306674912; // = 0xedb88320
   for ($n = 0; $n < 256; $n++) {
   $c = $n;
   for ($k = 0; $k < 8; $k++) {
   $c2 = ($c >> 1) & 0x7fffffff;
   if ($c & 1) $c = $z ^ ($c2); else $c = $c2;
   }
   $crc_table[$n] = $c;
   }
   
   // PNG file signature
   $result = pack("c*", 137,80,78,71,13,10,26,10);
   
   // IHDR chunk data:
   // width: 4 bytes
   // height: 4 bytes
   // bit depth: 1 byte (8 bits per RGB value)
   // color type: 1 byte (2 = RGB)
   // compression method: 1 byte (0 = deflate/inflate)
   // filter method: 1 byte (0 = adaptive filtering)
   // interlace method: 1 byte (0 = no interlace)
   $data = pack("c*", ($sx >> 24) & 255,
   ($sx >> 16) & 255,
   ($sx >> 8) & 255,
   $sx & 255,
   ($sy >> 24) & 255,
   ($sy >> 16) & 255,
   ($sy >> 8) & 255,
   $sy & 255,
   8,
   2,
   0,
   0,
   0);
   add_chunk("IHDR");
   
   // 以下不敢乱翻译，请自行参考
   // scanline:
   // filter byte: 0 = none
   // RGB bytes for the line
   // the scanline is compressed with "zlib", method 8 (RFC-1950):
   // compression method/flags code: 1 byte ($78 = method 8, 32k window)
   // additional flags/check bits: 1 byte ($01: FCHECK = 1, FDICT = 0, FLEVEL = 0)
   // compressed data blocks: n bytes
   // one block (RFC-1951):
   // bit 0: BFINAL: 1 for the last block
   // bit 1 and 2: BTYPE: 0 for no compression
   // next 2 bytes: LEN (LSB first)
   // next 2 bytes: one's complement of LEN
   // LEN bytes uncompressed data
   // check value: 4 bytes (Adler-32 checksum of the uncompressed data)
   //
   $len = ($sx * 3 + 1) * $sy;
   $data = pack("c*", 0x78, 0x01,
   1,
   $len & 255,
   ($len >> 8) & 255,
   255 - ($len & 255),
   255 - (($len >> 8) & 255));
   $start = strlen($data);
   $i2 = 0;
   for ($h = 0; $h < $sy; $h++) {
   $data .= chr(0);
   for ($w = 0; $w < $sx * 3; $w++) {
   $data .= $pixels[$i2++];
   }
   }
   
   
   // calculate a Adler32 checksum with the bytes data[start..len-1]
   $s1 = 1;
   $s2 = 0;
   for ($n = $start; $n < strlen($data); $n++) {
   $s1 = ($s1 + ord($data[$n])) % 65521;
   $s2 = ($s2 + $s1) % 65521;
   }
   $adler = ($s2 << 16) | $s1;
   
   $data .= chr(($adler >> 24) & 255);
   $data .= chr(($adler >> 16) & 255);
   $data .= chr(($adler >> 8) & 255);
   $data .= chr($adler & 255);
   add_chunk("IDAT");
   
   // IEND: marks the end of the PNG-file
   $data = "";
   add_chunk("IEND");
   
   // 列印图象
   
   echo($result);
  ?>
   
  //如何调用，其实很简单，将上面存为Timeimg.php
  //然后新建一个页面如下：
   
  <html>
   <head>
   <title>test</title>
   <meta http-equiv="Content-Type" content="text/html">
   </head>
   <body>
   <img src="Timeimg.php"> //以图象连接方式调用PHP文件
  </body>
  </html>