php实现图片缩略图的方法

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php实现图片缩略图的方法

本文使用php实现的图片缩略图，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，需要的朋友可以参考下本段代码。

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！

原文链接：http://www.phpfensi.com/php/20210722/17370.html

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