php实现图片缩略图的方法

本段代码实现功能有这些：

支持jpg,jpeg,gif,png,bmp图片格式，支持按原图片的比例进行缩放，可以选择在图片缩放的过程中是否需要对图片进行裁切，加入了图片质量控制，可以实现缩略图片质量最高化。

完整类的代码如下：

<?php
/**
* 功能：php生成缩略图片的类
*/
class resizeimage{
public $type;//图片类型
public $width;//实际宽度
public $height;//实际高度
public $resize_width;//改变后的宽度
public $resize_height;//改变后的高度
public $cut;//是否裁图
public $srcimg;//源图象 
public $dstimg;//目标图象地址
public $im;//临时创建的图象
public $quality;//图片质量
function resizeimage($img,$wid,$hei,$c,$dstpath,$quality=100){
$this->srcimg=$img;
$this->resize_width=$wid;
$this->resize_height=$hei;
$this->cut=$c;
$this->quality=$quality;
$this->type=strtolower(substr(strrchr($this->srcimg,'.'),1));//图片的类型
$this->initi_img();//初始化图象
$this -> dst_img($dstpath);//目标图象地址
@$this->width=imagesx($this->im);
@$this->height=imagesy($this->im);
$this->newimg();//生成图象
@imagedestroy($this->im);
}
function newimg(){
$resize_ratio=($this->resize_width)/($this->resize_height);//改变后的图象的比例
@$ratio=($this->width)/($this->height);//实际图象的比例
if(($this->cut)=='1'){//裁图
if($img_func==='imagepng'&&(str_replace('.','',php_version)>=512)){ //针对php版本大于5.12参数变化后的处理情况
$quality=9;
}
if($ratio>=$resize_ratio){//高度优先
$newimg=imagecreatetruecolor($this->resize_width,$this->resize_height);
imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,$this->resize_height,(($this->height)*$resize_ratio),$this->height);
imagejpeg($newimg,$this->dstimg,$this->quality);
}
if($ratio<$resize_ratio){//宽度优先
$newimg=imagecreatetruecolor($this->resize_width,$this->resize_height);
imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,$this->resize_height,$this->width,(($this->width)/$resize_ratio));
imagejpeg($newimg,$this->dstimg,$this->quality);
}
}else{//不裁图
if($ratio>=$resize_ratio){
$newimg=imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);
imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,($this->resize_width)/$ratio,$this->width,$this->height);
imagejpeg($newimg,$this->dstimg,$this->quality);
}
if($ratio<$resize_ratio){
@$newimg=imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);
@imagecopyresampled($newimg,$this->im,0,0,0,0,($this->resize_height)*$ratio,$this->resize_height,$this->width,$this->height);
@imagejpeg($newimg,$this->dstimg,$this->quality);
}
}
}
function initi_img(){//初始化图象
if($this->type=='jpg' || $this->type=='jpeg'){
$this->im=imagecreatefromjpeg($this->srcimg);
}
if($this->type=='gif'){
$this->im=imagecreatefromgif($this->srcimg);
}
if($this->type=='png'){
$this->im=imagecreatefrompng($this->srcimg);
}
if($this->type=='wbm'){
@$this->im=imagecreatefromwbmp($this->srcimg);
}
if($this->type=='bmp'){
$this->im=$this->imagecreatefrombmp($this->srcimg);
}
}
function dst_img($dstpath){//图象目标地址
$full_length=strlen($this->srcimg);
$type_length=strlen($this->type);
$name_length=$full_length-$type_length;
$name=substr($this->srcimg,0,$name_length-1);
$this->dstimg=$dstpath;
//echo $this->dstimg;
}
function imagecreatefrombmp($filename){ //自定义函数处理bmp图片
if(!$f1=fopen($filename,"rb"))returnfalse;
$file=unpack("vfile_type/vfile_size/vreserved/vbitmap_offset",fread($f1,14));
if($file['file_type']!=19778)returnfalse;
$bmp=unpack('vheader_size/vwidth/vheight/vplanes/vbits_per_pixel'.
'/vcompression/vsize_bitmap/vhoriz_resolution'.
'/vvert_resolution/vcolors_used/vcolors_important',fread($f1,40));
$bmp['colors']=pow(2,$bmp['bits_per_pixel']);
if($bmp['size_bitmap']==0)$bmp['size_bitmap']=$file['file_size']-$file['bitmap_offset'];
$bmp['bytes_per_pixel']=$bmp['bits_per_pixel']/8;
$bmp['bytes_per_pixel2']=ceil($bmp['bytes_per_pixel']);
$bmp['decal']=($bmp['width']*$bmp['bytes_per_pixel']/4);
$bmp['decal']-=floor($bmp['width']*$bmp['bytes_per_pixel']/4);
$bmp['decal']=4-(4*$bmp['decal']);
if($bmp['decal']==4)$bmp['decal']=0;
$palette=array();
if($bmp['colors']<16777216)
{
$palette=unpack('v'.$bmp['colors'],fread($f1,$bmp['colors']*4));
}
$img=fread($f1,$bmp['size_bitmap']);
$vide=chr(0);
$res=imagecreatetruecolor($bmp['width'],$bmp['height']);
$p=0;
$y=$bmp['height']-1;
while($y>=0)
{
$x=0;
while($x<$bmp['width'])
{
if($bmp['bits_per_pixel']==24)
$color=unpack("v",substr($img,$p,3).$vide);
elseif($bmp['bits_per_pixel']==16)
{
$color=unpack("n",substr($img,$p,2));
$color[1]=$palette[$color[1]+1];
}
elseif($bmp['bits_per_pixel']==8)
{
$color=unpack("n",$vide.substr($img,$p,1));
$color[1]=$palette[$color[1]+1];
}
elseif($bmp['bits_per_pixel']==4)
{
$color=unpack("n",$vide.substr($img,floor($p),1));
if(($p*2)%2==0)$color[1]=($color[1]>>4);else$color[1]=($color[1]&0x0f);
$color[1]=$palette[$color[1]+1];
}
elseif($bmp['bits_per_pixel']==1)
{
$color=unpack("n",$vide.substr($img,floor($p),1));
if(($p*8)%8==0)$color[1]=$color[1]>>7;
elseif(($p*8)%8==1)$color[1]=($color[1]&0x40)>>6;
elseif(($p*8)%8==2)$color[1]=($color[1]&0x20)>>5;
elseif(($p*8)%8==3)$color[1]=($color[1]&0x10)>>4;
elseif(($p*8)%8==4)$color[1]=($color[1]&0x8)>>3;
elseif(($p*8)%8==5)$color[1]=($color[1]&0x4)>>2;
elseif(($p*8)%8==6)$color[1]=($color[1]&0x2)>>1;
elseif(($p*8)%8==7)$color[1]=($color[1]&0x1);
$color[1]=$palette[$color[1]+1];
}
else
returnfalse;
imagesetpixel($res,$x,$y,$color[1]);
$x++;
$p+=$bmp['bytes_per_pixel'];
}
$y--;
$p+=$bmp['decal'];
}
fclose($f1);
return$res;
}
}
?>

使用方法很简单代码如下：

$resizeimage=new resizeimage('upload/abc.bmp', '120', '90', '0', 'upload/xabc.bmp');

以上代码是小编给大家分享的php实现图片缩略图的方法，希望对大家有所帮助！