php 图片缩略图的实现方法

功能：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\');