PHP转换图片格式为JPG并自动缩放成指定大小

发布时间：2020-12-13 20:35:19 所属栏目：PHP教程来源：网络整理

导读：最近给朋友修改网站时，网小编发现有一些网站的图片是PNG格式，并且图片文件非常大，差不多都在200KB以上，而同像素的JPG图片会小很多，于是在网上找了一下教程，现在将PHP将指定的图片格式转换为JPG并自动缩放成指定大小的方法发布给大家，支持JPG、BMP、PN

最近给朋友修改网站时，网小编发现有一些网站的图片是PNG格式，并且图片文件非常大，差不多都在200KB以上，而同像素的JPG图片会小很多，于是在网上找了一下教程，现在将PHP将指定的图片格式转换为JPG并自动缩放成指定大小的方法发布给大家，支持JPG、BMP、PNG和GIF格式。

不说别的了，直接上代码，此代码不可能直接复制到你的网站使用，需要你懂一些PHP知识，如果您不懂PHP，建议阅读提供的PHP中文手册。

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引用的内容：[www.veryhuo.com]

<?php

function ImageCreateFromBMP( $filename )
{
if ( ! $f1 = fopen ( $filename,"rb" )) return FALSE ;

$FILE = unpack ( "vfile_type/Vfile_size/Vreserved/Vbitmap_offset",fread ( $f1,14 ));
if ( $FILE [ 'file_type' ] != 19778 ) return FALSE ;

$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 (( $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",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
return FALSE ;
imagesetpixel( $res,$X,$Y,$COLOR [ 1 ]);
$X ++ ;
$P += $BMP [ 'bytes_per_pixel' ];
}
$Y -- ;
$P += $BMP [ 'decal' ];
}

fclose ( $f1 );
return $res ;
}

//

（编辑：李大同）

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