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];}elsereturnFALSE;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！