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图片抓取失败问题

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Jun 23, 2016 pm 02:27 PM

抓取图片

最近要抓取智库百科中的词条，但是词条中的图片抓取出现了问题，这是其中一个图片链接。
http://wiki.mbalib.com/w/images/2/22/%E6%B3%9B%E6%88%90%E6%9C%AC%E7%9A%84%E7%89%B9%E5%BE%81.jpg

无论是用file_get_contents，还是ob_start后readfile，还是用curl，还是snoopy，抓取下来的图片都是损坏的，抓下来的数据比原图小，但我看了一下这个站的图片貌似并没有设置防盗链或cookie验证之类的，求解决方法

回复讨论(解决方案)

他传送的图片数据是 gzip 压缩的，需要使用 gzdecode 函数解码（php5>=5.4.0 已添加进 gzip 扩展了

$url = 'http://wiki.mbalib.com/w/images/2/22/%E6%B3%9B%E6%88%90%E6%9C%AC%E7%9A%84%E7%89%B9%E5%BE%81.jpg';$s = file_get_contents($url);echo gzdecode($s);

如果你的 php 版本还没有那么高，可以自己写代码。网上也可以搜索到。
给一个老外的

function gzdecode($data) {   $len = strlen($data);   if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {     return $data;  // Not GZIP format (See RFC 1952)   }   $method = ord(substr($data,2,1));  // Compression method   $flags  = ord(substr($data,3,1));  // Flags   if ($flags & 31 != $flags) {     // Reserved bits are set -- NOT ALLOWED by RFC 1952     return data;   }   // NOTE: $mtime may be negative (PHP integer limitations)   $mtime = unpack("V", substr($data,4,4));   $mtime = $mtime[1];   $xfl   = substr($data,8,1);   $os    = substr($data,8,1);   $headerlen = 10;   $extralen  = 0;   $extra     = "";   if ($flags & 4) {     // 2-byte length prefixed EXTRA data in header     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $extralen = unpack("v",substr($data,8,2));     $extralen = $extralen[1];     if ($len - $headerlen - 2 - $extralen < 8) {       return false;    // Invalid format     }     $extra = substr($data,10,$extralen);     $headerlen += 2 + $extralen;   }   $filenamelen = 0;   $filename = "";   if ($flags & 8) {     // C-style string file NAME data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $filenamelen = strpos(substr($data,8+$extralen),chr(0));     if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {       return false;    // Invalid format     }     $filename = substr($data,$headerlen,$filenamelen);     $headerlen += $filenamelen + 1;   }   $commentlen = 0;   $comment = "";   if ($flags & 16) {     // C-style string COMMENT data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));     if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {       return false;    // Invalid header format     }     $comment = substr($data,$headerlen,$commentlen);     $headerlen += $commentlen + 1;   }   $headercrc = "";   if ($flags & 1) {     // 2-bytes (lowest order) of CRC32 on header present     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;     $headercrc = unpack("v", substr($data,$headerlen,2));     $headercrc = $headercrc[1];     if ($headercrc != $calccrc) {       return false;    // Bad header CRC     }     $headerlen += 2;   }   // GZIP FOOTER - These be negative due to PHP's limitations   $datacrc = unpack("V",substr($data,-8,4));   $datacrc = $datacrc[1];   $isize = unpack("V",substr($data,-4));   $isize = $isize[1];   // Perform the decompression:   $bodylen = $len-$headerlen-8;   if ($bodylen < 1) {     // This should never happen - IMPLEMENTATION BUG!     return null;   }   $body = substr($data,$headerlen,$bodylen);   $data = "";   if ($bodylen > 0) {     switch ($method) {       case 8:         // Currently the only supported compression method:         $data = gzinflate($body);         break;       default:         // Unknown compression method         return false;     }   } else {     // I'm not sure if zero-byte body content is allowed.     // Allow it for now...  Do nothing...   }   // Verifiy decompressed size and CRC32:   // NOTE: This may fail with large data sizes depending on how   //       PHP's integer limitations affect strlen() since $isize   //       may be negative for large sizes.   if ($isize != strlen($data) || crc32($data) != $datacrc) {     // Bad format!  Length or CRC doesn't match!     return false;   }   return $data; }

他传送的图片数据是 gzip 压缩的，需要使用 gzdecode 函数解码（php5>=5.4.0 已添加进 gzip 扩展了

$url = 'http://wiki.mbalib.com/w/images/2/22/%E6%B3%9B%E6%88%90%E6%9C%AC%E7%9A%84%E7%89%B9%E5%BE%81.jpg';$s = file_get_contents($url);echo gzdecode($s);

如果你的 php 版本还没有那么高，可以自己写代码。网上也可以搜索到。
给一个老外的

function gzdecode($data) {   $len = strlen($data);   if ($len < 18 || strcmp(substr($data,0,2),"\x1f\x8b")) {     return $data;  // Not GZIP format (See RFC 1952)   }   $method = ord(substr($data,2,1));  // Compression method   $flags  = ord(substr($data,3,1));  // Flags   if ($flags & 31 != $flags) {     // Reserved bits are set -- NOT ALLOWED by RFC 1952     return data;   }   // NOTE: $mtime may be negative (PHP integer limitations)   $mtime = unpack("V", substr($data,4,4));   $mtime = $mtime[1];   $xfl   = substr($data,8,1);   $os    = substr($data,8,1);   $headerlen = 10;   $extralen  = 0;   $extra     = "";   if ($flags & 4) {     // 2-byte length prefixed EXTRA data in header     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $extralen = unpack("v",substr($data,8,2));     $extralen = $extralen[1];     if ($len - $headerlen - 2 - $extralen < 8) {       return false;    // Invalid format     }     $extra = substr($data,10,$extralen);     $headerlen += 2 + $extralen;   }   $filenamelen = 0;   $filename = "";   if ($flags & 8) {     // C-style string file NAME data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $filenamelen = strpos(substr($data,8+$extralen),chr(0));     if ($filenamelen === false || $len - $headerlen - $filenamelen - 1 < 8) {       return false;    // Invalid format     }     $filename = substr($data,$headerlen,$filenamelen);     $headerlen += $filenamelen + 1;   }   $commentlen = 0;   $comment = "";   if ($flags & 16) {     // C-style string COMMENT data in header     if ($len - $headerlen - 1 < 8) {       return false;    // Invalid format     }     $commentlen = strpos(substr($data,8+$extralen+$filenamelen),chr(0));     if ($commentlen === false || $len - $headerlen - $commentlen - 1 < 8) {       return false;    // Invalid header format     }     $comment = substr($data,$headerlen,$commentlen);     $headerlen += $commentlen + 1;   }   $headercrc = "";   if ($flags & 1) {     // 2-bytes (lowest order) of CRC32 on header present     if ($len - $headerlen - 2 < 8) {       return false;    // Invalid format     }     $calccrc = crc32(substr($data,0,$headerlen)) & 0xffff;     $headercrc = unpack("v", substr($data,$headerlen,2));     $headercrc = $headercrc[1];     if ($headercrc != $calccrc) {       return false;    // Bad header CRC     }     $headerlen += 2;   }   // GZIP FOOTER - These be negative due to PHP's limitations   $datacrc = unpack("V",substr($data,-8,4));   $datacrc = $datacrc[1];   $isize = unpack("V",substr($data,-4));   $isize = $isize[1];   // Perform the decompression:   $bodylen = $len-$headerlen-8;   if ($bodylen < 1) {     // This should never happen - IMPLEMENTATION BUG!     return null;   }   $body = substr($data,$headerlen,$bodylen);   $data = "";   if ($bodylen > 0) {     switch ($method) {       case 8:         // Currently the only supported compression method:         $data = gzinflate($body);         break;       default:         // Unknown compression method         return false;     }   } else {     // I'm not sure if zero-byte body content is allowed.     // Allow it for now...  Do nothing...   }   // Verifiy decompressed size and CRC32:   // NOTE: This may fail with large data sizes depending on how   //       PHP's integer limitations affect strlen() since $isize   //       may be negative for large sizes.   if ($isize != strlen($data) || crc32($data) != $datacrc) {     // Bad format!  Length or CRC doesn't match!     return false;   }   return $data; }

非常感谢，长知识了

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