【GIFDecoder】GIFDecoder的排错以及修改另附完整代码和demo
2015-05-21 11:06
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前言
好久没有写技术类的博客了,今天有些小的收获,记录下来,留作备份Gif图片的处理
由于业务需求,需要对gif动图的第一帧进行截取,然后我就搜索,发现了GIFDecoder这样的一个类,是做gif图片的处理的,怎奈国内人博客环境还是那么差,各种网站博客到处抄抄抄,没有一个完整的内容,经过多个站的资料整理,终于能用了。出现了异常
在运行demo的时候,遇到了显示错误的问题Notice: Undefined offset: 4 in /Applications/XAMPP/xamppfiles/htdocs/giftest/gifdecoder.class.php on line 83
查看源码发现83行是这样的
function GIFReadExtensions() { GIFDecoder::GIFGetByte(1); if ($this->GIF_buffer [0] == 0xff) { for (;;) { GIFDecoder::GIFGetByte(1); if (( $u = $this->GIF_buffer [0] ) == 0x00) { break; } GIFDecoder::GIFGetByte($u); if ($u == 0x03) { $this->GIF_anloop = ( $this->GIF_buffer [1] | $this->GIF_buffer [2] << 8 ); } } } else { for (;;) { GIFDecoder::GIFGetByte(1); if (( $u = $this->GIF_buffer [0] ) == 0x00) { break; } GIFDecoder::GIFGetByte($u); if ($u == 0x04) { if ($this->GIF_buffer [4] & 0x80) { //这里是第83行 $this->GIF_dispos [] = ( $this->GIF_buffer [0] >> 2 ) - 1; } else { $this->GIF_dispos [] = ( $this->GIF_buffer [0] >> 2 ) - 0; } $this->GIF_delays [] = ( $this->GIF_buffer [1] | $this->GIF_buffer [2] << 8 ); if ($this->GIF_buffer [3]) { $this->GIF_TransparentI = $this->GIF_buffer [3]; } } } } }
原因
经过搜索引擎的努力,我得到的比较正规的解释是offset:接下去的数字是出错的数组下标,一般是超出了数组的取值范围,如定义了数组A[]有10个元数,如果出现了A[10]就会出现错误(Notice: Undefined offset: 10 ….),因为数组的下标是从0开始的,所以这个数组的下标就只能是0~9.
所以,原因就是
数组找不到下标为4的元素
解决方案
我们需要判断下标是不是存在if (isset($this->GIF_buffer [4]) & 0x80) {
酱紫就搞定啦,啦啦啦~
源码
<?php /** * GIFDecoder <br/> * * 日期: 2015年05月21日 <br/> * 原作者: 不详 <br/> * 修改: CalvinLee <br/> * * * <code> * require_once("gifdecoder.class.php"); * * $FIC = "test.gif"; * //获取gif的第一帧进行保存 * if (file_exists($FIC)) { * $GIF_frame = fread(fopen($FIC, 'rb'), filesize($FIC)); * $decoder = new GIFDecoder($GIF_frame); * $frames = $decoder->GIFGetFrames(); * $i = 0; * $fname = rand(1000, 9999). $FIC . "_0$i.png"; * $hfic = fopen("" . $fname, "wb"); * fwrite($hfic, $frames [$i]); * fclose($hfic); * } * </code> * * * @copyright (c) 2015, Calvin Lee * @author Calvin Lee <diandianxiyu_@live.cn> */ Class GIFDecoder { public $GIF_TransparentR = -1; public $GIF_TransparentG = -1; public $GIF_TransparentB = -1; public $GIF_TransparentI = 0; public $GIF_buffer = array(); public $GIF_arrays = array(); public $GIF_delays = array(); public $GIF_dispos = array(); public $GIF_stream = ""; public $GIF_string = ""; public $GIF_bfseek = 0; public $GIF_anloop = 0; public $GIF_screen = array(); public $GIF_global = array(); public $GIF_sorted; public $GIF_colorS; public $GIF_colorC; public $GIF_colorF; function GIFDecoder($GIF_pointer) { $this->GIF_stream = $GIF_pointer; GIFDecoder::GIFGetByte(6); GIFDecoder::GIFGetByte(7); $this->GIF_screen = $this->GIF_buffer; $this->GIF_colorF = $this->GIF_buffer [4] & 0x80 ? 1 : 0; $this->GIF_sorted = $this->GIF_buffer [4] & 0x08 ? 1 : 0; $this->GIF_colorC = $this->GIF_buffer [4] & 0x07; $this->GIF_colorS = 2 << $this->GIF_colorC; if ($this->GIF_colorF == 1) { GIFDecoder::GIFGetByte(3 * $this->GIF_colorS); $this->GIF_global = $this->GIF_buffer; } for ($cycle = 1; $cycle;) { if (GIFDecoder::GIFGetByte(1)) { switch ($this->GIF_buffer [0]) { case 0x21: GIFDecoder::GIFReadExtensions(); break; case 0x2C: GIFDecoder::GIFReadDescriptor(); break; case 0x3B: $cycle = 0; break; } } else { $cycle = 0; } } } function GIFReadExtensions() { GIFDecoder::GIFGetByte(1); if ($this->GIF_buffer [0] == 0xff) { for (;;) { GIFDecoder::GIFGetByte(1); if (( $u = $this->GIF_buffer [0] ) == 0x00) { break; } GIFDecoder::GIFGetByte($u); if ($u == 0x03) { $this->GIF_anloop = ( $this->GIF_buffer [1] | $this->GIF_buffer [2] << 8 ); } } } else { for (;;) { GIFDecoder::GIFGetByte(1); if (( $u = $this->GIF_buffer [0] ) == 0x00) { break; } GIFDecoder::GIFGetByte($u); if ($u == 0x04) { if (isset($this->GIF_buffer [4]) & 0x80) { $this->GIF_dispos [] = ( $this->GIF_buffer [0] >> 2 ) - 1; } else { $this->GIF_dispos [] = ( $this->GIF_buffer [0] >> 2 ) - 0; } $this->GIF_delays [] = ( $this->GIF_buffer [1] | $this->GIF_buffer [2] << 8 ); if ($this->GIF_buffer [3]) { $this->GIF_TransparentI = $this->GIF_buffer [3]; } } } } } function GIFReadDescriptor() { $GIF_screen = Array(); GIFDecoder::GIFGetByte(9); $GIF_screen = $this->GIF_buffer; $GIF_colorF = $this->GIF_buffer [8] & 0x80 ? 1 : 0; if ($GIF_colorF) { $GIF_code = $this->GIF_buffer [8] & 0x07; $GIF_sort = $this->GIF_buffer [8] & 0x20 ? 1 : 0; } else { $GIF_code = $this->GIF_colorC; $GIF_sort = $this->GIF_sorted; } $GIF_size = 2 << $GIF_code; $this->GIF_screen [4] &= 0x70; $this->GIF_screen [4] |= 0x80; $this->GIF_screen [4] |= $GIF_code; if ($GIF_sort) { $this->GIF_screen [4] |= 0x08; } //GIF Data Begin if ($this->GIF_TransparentI) { $this->GIF_string = "GIF89a"; } else { $this->GIF_string = "GIF87a"; } GIFDecoder::GIFPutByte($this->GIF_screen); if ($GIF_colorF == 1) { GIFDecoder::GIFGetByte(3 * $GIF_size); if ($this->GIF_TransparentI) { $this->GIF_TransparentR = $this->GIF_buffer [3 * $this->GIF_TransparentI + 0]; $this->GIF_TransparentG = $this->GIF_buffer [3 * $this->GIF_TransparentI + 1]; $this->GIF_TransparentB = $this->GIF_buffer [3 * $this->GIF_TransparentI + 2]; } GIFDecoder::GIFPutByte($this->GIF_buffer); } else { if ($this->GIF_TransparentI) { $this->GIF_TransparentR = $this->GIF_global [3 * $this->GIF_TransparentI + 0]; $this->GIF_TransparentG = $this->GIF_global [3 * $this->GIF_TransparentI + 1]; $this->GIF_TransparentB = $this->GIF_global [3 * $this->GIF_TransparentI + 2]; } GIFDecoder::GIFPutByte($this->GIF_global); } if ($this->GIF_TransparentI) { $this->GIF_string .= "!\xF9\x04\x1\x0\x0" . chr($this->GIF_TransparentI) . "\x0"; } $this->GIF_string .= chr(0x2C); $GIF_screen [8] &= 0x40; GIFDecoder::GIFPutByte($GIF_screen); GIFDecoder::GIFGetByte(1); GIFDecoder::GIFPutByte($this->GIF_buffer); for (;;) { GIFDecoder::GIFGetByte(1); GIFDecoder::GIFPutByte($this->GIF_buffer); if (( $u = $this->GIF_buffer [0] ) == 0x00) { break; } GIFDecoder::GIFGetByte($u); GIFDecoder::GIFPutByte($this->GIF_buffer); } $this->GIF_string .= chr(0x3B); //GIF Data End $gif_array = &$this->GIF_arrays; $gif_array[] = $this->GIF_string; } function GIFGetByte($len) { $this->GIF_buffer = Array(); for ($i = 0; $i < $len; $i++) { if ($this->GIF_bfseek > strlen($this->GIF_stream)) { return 0; } $this->GIF_buffer[] = ord($this->GIF_stream { $this->GIF_bfseek++}); } return 1; } function GIFPutByte($bytes) { foreach ($bytes as $byte) { $this->GIF_string .= chr($byte); } } function GIFGetFrames() { return ( $this->GIF_arrays ); } function GIFGetDelays() { return ( $this->GIF_delays ); } function GIFGetLoop() { return ( $this->GIF_anloop ); } function GIFGetDisposal() { return ( $this->GIF_dispos ); } function GIFGetTransparentR() { return ( $this->GIF_TransparentR ); } function GIFGetTransparentG() { return ( $this->GIF_TransparentG ); } function GIFGetTransparentB() { return ( $this->GIF_TransparentB ); } } ?>
后记
小的知识积累最后会有质变善于总结永远没有坏处
一个功能写三遍就会变得不一样,如果还一样的话那就是自己的问题了
后后记
后来发现这个类在Yii2中还是不能使用,识别不出gif里面的图片,所以,我又去github上找到了这个类的2.0版https://github.com/xurei/GIFDecoder_optimized
下面是用的源码,已经加上了namespace和注释
<?php namespace common\components\helper; /* ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFDecoder Version 2.0 by László Zsidi :: Optimized version by xurei :: :: Created at 2007. 02. 01. '07.47.AM' :: :: Updated at 2009. 06. 23. '06.00.AM' :: ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: * * * * <code> * require_once("gifdecoder.class.php"); * * $FIC = "test.gif"; * //获取gif的第一帧进行保存 * if (file_exists($FIC)) { * $GIF_frame = fread(fopen($FIC, 'rb'), filesize($FIC)); * $decoder = new GIFDecoder($GIF_frame); * $frames = $decoder->GIFGetFrames(); * $i = 0; * $fname = rand(1000, 9999). $FIC . "_0$i.png"; * $hfic = fopen("" . $fname, "wb"); * fwrite($hfic, $frames [$i]); * fclose($hfic); * } * </code> * * * * */ use SplFixedArray; class GIFDecoder { var $GIF_TransparentR = -1; var $GIF_TransparentG = -1; var $GIF_TransparentB = -1; var $GIF_TransparentI = 0; var $GIF_buffer = null; var $GIF_arrays = Array ( ); var $GIF_delays = Array ( ); var $GIF_dispos = Array ( ); var $GIF_stream = ""; var $GIF_string = ""; var $GIF_bfseek = 0; var $GIF_anloop = 0; //xurei - frames metadata var $GIF_frames_meta = Array(); var $GIF_screen = Array ( ); var $GIF_global = Array ( ); //global color map var $GIF_sorted; var $GIF_colorS; // var $GIF_colorC; //Size of global color table var $GIF_colorF; //if 1, global color table follows image descriptor /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFDecoder ( $GIF_pointer ) :: */ function __construct ( $GIF_pointer ) { $this->GIF_stream = $GIF_pointer; GIFDecoder::GIFGetByte ( 6 ); GIFDecoder::GIFGetByte ( 7 ); $this->GIF_screen = $this->GIF_buffer; $this->GIF_colorF = $this->GIF_buffer [ 4 ] & 0x80 ? 1 : 0; $this->GIF_sorted = $this->GIF_buffer [ 4 ] & 0x08 ? 1 : 0; $this->GIF_colorC = $this->GIF_buffer [ 4 ] & 0x07; $this->GIF_colorS = 2 << $this->GIF_colorC; if ( $this->GIF_colorF == 1 ) { GIFDecoder::GIFGetByte ( 3 * $this->GIF_colorS ); $this->GIF_global = $this->GIF_buffer; } for ( $cycle = 1; $cycle; ) { if ( GIFDecoder::GIFGetByte ( 1 ) ) { switch ( $this->GIF_buffer [ 0 ] ) { case 0x21: GIFDecoder::GIFReadExtensions ( ); break; case 0x2C: GIFDecoder::GIFReadDescriptor ( ); break; case 0x3B: $cycle = 0; break; } } else { $cycle = 0; } } } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFReadExtension ( ) :: */ function GIFReadExtensions ( ) { GIFDecoder::GIFGetByte ( 1 ); if ( $this->GIF_buffer [ 0 ] == 0xff ) { for ( ; ; ) { GIFDecoder::GIFGetByte ( 1 ); if ( ( $u = $this->GIF_buffer [ 0 ] ) == 0x00 ) { break; } GIFDecoder::GIFGetByte ( $u ); if ( $u == 0x03 ) { $this->GIF_anloop = ( $this->GIF_buffer [ 1 ] | $this->GIF_buffer [ 2 ] << 8 ); } } } else { for ( ; ; ) { GIFDecoder::GIFGetByte ( 1 ); if ( ( $u = $this->GIF_buffer [ 0 ] ) == 0x00 ) { break; } GIFDecoder::GIFGetByte ( $u ); if ( $u == 0x04 ) { $buf4 = count($this->GIF_buffer) >= 5 ? $this->GIF_buffer [ 4 ] : 0; if ( $buf4 & 0x80 ) { $this->GIF_dispos [ ] = ( $this->GIF_buffer [ 0 ] >> 2 ) - 1; } else { $this->GIF_dispos [ ] = ( $this->GIF_buffer [ 0 ] >> 2 ) - 0; } $this->GIF_delays [ ] = ( $this->GIF_buffer [ 1 ] | $this->GIF_buffer [ 2 ] << 8 ); if ( $this->GIF_buffer [ 3 ] ) { $this->GIF_TransparentI = $this->GIF_buffer [ 3 ]; } } } } } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFReadDescriptor ( ) :: */ function GIFReadDescriptor ( ) { $GIF_screen = Array ( ); GIFDecoder::GIFGetByte ( 9 ); //xurei - metadata saving $this->GIF_frames_meta[] = array( 'left'=>$this->GIF_buffer[0] + ($this->GIF_buffer[1] << 8), 'top'=>$this->GIF_buffer[2] + ($this->GIF_buffer[3] << 8), 'width'=>$this->GIF_buffer[4] + ($this->GIF_buffer[5] << 8), 'height'=>$this->GIF_buffer[6] + ($this->GIF_buffer[7] << 8), ); $GIF_screen = $this->GIF_buffer; $GIF_colorF = $this->GIF_buffer [ 8 ] & 0x80 ? 1 : 0; if ( $GIF_colorF ) { $GIF_code = $this->GIF_buffer [ 8 ] & 0x07; $GIF_sort = $this->GIF_buffer [ 8 ] & 0x20 ? 1 : 0; } else { $GIF_code = $this->GIF_colorC; $GIF_sort = $this->GIF_sorted; } $GIF_size = 2 << $GIF_code; $this->GIF_screen [ 4 ] &= 0x70; $this->GIF_screen [ 4 ] |= 0x80; $this->GIF_screen [ 4 ] |= $GIF_code; if ( $GIF_sort ) { $this->GIF_screen [ 4 ] |= 0x08; } /* * * GIF Data Begin * */ if ( $this->GIF_TransparentI ) { $this->GIF_string = "GIF89a"; } else { $this->GIF_string = "GIF87a"; } GIFDecoder::GIFPutByte ( $this->GIF_screen ); if ( $GIF_colorF == 1 ) { GIFDecoder::GIFGetByte ( 3 * $GIF_size ); if ( $this->GIF_TransparentI ) { $this->GIF_TransparentR = $this->GIF_buffer [ 3 * $this->GIF_TransparentI + 0 ]; $this->GIF_TransparentG = $this->GIF_buffer [ 3 * $this->GIF_TransparentI + 1 ]; $this->GIF_TransparentB = $this->GIF_buffer [ 3 * $this->GIF_TransparentI + 2 ]; } GIFDecoder::GIFPutByte ( $this->GIF_buffer ); } else { if ( $this->GIF_TransparentI ) { $this->GIF_TransparentR = $this->GIF_global [ 3 * $this->GIF_TransparentI + 0 ]; $this->GIF_TransparentG = $this->GIF_global [ 3 * $this->GIF_TransparentI + 1 ]; $this->GIF_TransparentB = $this->GIF_global [ 3 * $this->GIF_TransparentI + 2 ]; } GIFDecoder::GIFPutByte ( $this->GIF_global ); } if ( $this->GIF_TransparentI ) { $this->GIF_string .= "!\xF9\x04\x1\x0\x0". chr ( $this->GIF_TransparentI ) . "\x0"; } $this->GIF_string .= chr ( 0x2C ); $GIF_screen [ 8 ] &= 0x40; GIFDecoder::GIFPutByte ( $GIF_screen ); GIFDecoder::GIFGetByte ( 1 ); GIFDecoder::GIFPutByte ( $this->GIF_buffer ); for ( ; ; ) { GIFDecoder::GIFGetByte ( 1 ); GIFDecoder::GIFPutByte ( $this->GIF_buffer ); if ( ( $u = $this->GIF_buffer [ 0 ] ) == 0x00 ) { break; } /*for ($i=0; $i!=$u; ++$i) { $this->GIF_string .= $this->GIF_stream { $this->GIF_bfseek++ }; }*/ $this->GIF_string .= substr($this->GIF_stream, $this->GIF_bfseek, $u); $this->GIF_bfseek += $u; //GIFDecoder::GIFGetByte ( $u ); //GIFDecoder::GIFPutByte ( $this->GIF_buffer ); } $this->GIF_string .= chr ( 0x3B ); /* * * GIF Data End * */ $this->GIF_arrays [ ] = $this->GIF_string; } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetByte ( $len ) :: */ function GIFGetByte ( $len ) { $this->GIF_buffer = new SplFixedArray($len); $l = strlen ( $this->GIF_stream ); for ( $i = 0; $i < $len; $i++ ) { if ( $this->GIF_bfseek > $l ) { $this->GIF_buffer->setSize($i); return 0; } $this->GIF_buffer [$i] = ord ( $this->GIF_stream { $this->GIF_bfseek++ } ); } return 1; } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFPutByte ( $bytes ) :: */ function GIFPutByte ( $bytes ) { $out = ''; foreach ( $bytes as $byte ) { $out .= chr($byte); } $this->GIF_string .= $out; } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: PUBLIC FUNCTIONS :: :: :: GIFGetFrames ( ) :: */ function GIFGetFrames ( ) { return ( $this->GIF_arrays ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetFramesMeta ( ) :: :: xurei - returns metadata as an array of arrays */ function GIFGetFramesMeta ( ) { return ( $this->GIF_frames_meta ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetDelays ( ) :: */ function GIFGetDelays ( ) { return ( $this->GIF_delays ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetLoop ( ) :: */ function GIFGetLoop ( ) { return ( $this->GIF_anloop ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetDisposal ( ) :: */ function GIFGetDisposal ( ) { return ( $this->GIF_dispos ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetTransparentR ( ) :: */ function GIFGetTransparentR ( ) { return ( $this->GIF_TransparentR ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetTransparentG ( ) :: */ function GIFGetTransparentG ( ) { return ( $this->GIF_TransparentG ); } /* ::::::::::::::::::::::::::::::::::::::::::::::::::: :: :: GIFGetTransparentB ( ) :: */ function GIFGetTransparentB ( ) { return ( $this->GIF_TransparentB ); } }
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