/*

* 说明：生成随机码，并用图形方式显示随机码。

*/

$ViewRandomCode = mt_rand(1000,10000);

session_start();

$_SESSION['checksum'] = $ViewRandomCode;

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 = 55;

$sy = 21;

$pixels = rand(100,99990)%2?”qwer”:”";

// 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);

}

}

$checknum = isset($ViewRandomCode)?$ViewRandomCode:1234;

$h = (int)($checknum/100);

$m = (int)($checknum%100);

$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);

// set_4pixel(0, 0, 0, 26, 7);

// set_4pixel(0, 0, 0, 26, 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) & 0×7fffffff;

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*”, 0×78, 0×01,

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);

?>