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：
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',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'],$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",2));
$COLOR[1]=$PALETTE[$COLOR[1]+1];
}
elseif($BMP['bits_per_pixel']==8)
{
$COLOR=unpack("n",$VIDE.substr($IMG,1));
$COLOR[1]=$PALETTE[$COLOR[1]+1];
}
elseif($BMP['bits_per_pixel']==4)
{
$COLOR=unpack("n",floor($P),1));
if(($P2)%2==0)$COLOR[1]=($COLOR[1]>>4);else$COLOR[1]=($COLOR[1]&0x0F);
$COLOR[1]=$PALETTE[$COLOR[1]+1];
}
elseif($BMP['bits_per_pixel']==1)
{
$COLOR=unpack("n",1));
if(($P8)%8==0)$COLOR[1]=$COLOR[1]>>7;
elseif(($P8)%8==1)$COLOR[1]=($COLOR[1]&0x40)>>6;
elseif(($P8)%8==2)$COLOR[1]=($COLOR[1]&0x20)>>5;
elseif(($P8)%8==3)$COLOR[1]=($COLOR[1]&0x10)>>4;
elseif(($P8)%8==4)$COLOR[1]=($COLOR[1]&0x8)>>3;
elseif(($P8)%8==5)$COLOR[1]=($COLOR[1]&0x4)>>2;
elseif(($P8)%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;
}
}
?>
另外一个强大的PHP图片缩略图类：PHPThumb
该类除了缩放图片外，还能将图片转换成不同的格式输出（比如将GIF格式的图片输出为PNG格式），其特色功能还包括色彩、特效等
官方网址：http://PHPthumb.sourceforge.net/
We'll be using PHPThumb,the open source PHP script to generate thumbnails on the fly.
Download and extract PHPThumb to somewhere in your website folder. Now to use a rounded corner thumbnail of an image,simply use the img tag of HTML with src as
Adjust the path to PHPThumb according to where you place the PHPThumb files.
