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
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 );
}
}
