图片无损压缩

<?php
error_reporting( E_ALL ); 

imagezoom('1.jpg', '2.jpg', 1280, 720, ''); 


function imagezoom( $srcimage, $dstimage, $dst_width, $dst_height, $backgroundcolor ) { 
    if ( PHP_OS == 'WINNT' ) { 
        $srcimage = iconv('UTF-8', 'GBK', $srcimage); 
        $dstimage = iconv('UTF-8', 'GBK', $dstimage); 
    } 
    $dstimg = imagecreatetruecolor( $dst_width, $dst_height ); 
    $color = imagecolorallocate($dstimg 
        , hexdec(substr($backgroundcolor, 1, 2)) 
        , hexdec(substr($backgroundcolor, 3, 2)) 
        , hexdec(substr($backgroundcolor, 5, 2)) 
    ); 
    imagefill($dstimg, 0, 0, $color); 
    if ( !$arr=getimagesize($srcimage) ) { 
        echo "ÒªÉú³ÉËõÂÔͼµÄÎļþ²»´æÔÚ"; 
        exit; 
    } 
    $src_width = $arr[0]; 
    $src_height = $arr[1]; 
    $srcimg = null; 
    $method = getcreatemethod( $srcimage ); 
    if ( $method ) { 
        eval( '$srcimg = ' . $method . ';' ); 
    } 
    $dst_x = 0; 
    $dst_y = 0; 
    $dst_w = $dst_width; 
    $dst_h = $dst_height; 
    if ( ($dst_width / $dst_height - $src_width / $src_height) > 0 ) { 
        $dst_w = $src_width * ( $dst_height / $src_height ); 
        $dst_x = ( $dst_width - $dst_w ) / 2; 
    } elseif ( ($dst_width / $dst_height - $src_width / $src_height) < 0 ) { 
        $dst_h = $src_height * ( $dst_width / $src_width ); 
        $dst_y = ( $dst_height - $dst_h ) / 2; 
    } 
    imagecopyresampled($dstimg, $srcimg, $dst_x 
        , $dst_y, 0, 0, $dst_w, $dst_h, $src_width, $src_height); 
    $arr = array( 
        'jpg' => 'imagejpeg' 
        , 'jpeg' => 'imagejpeg' 
        , 'png' => 'imagepng' 
        , 'gif' => 'imagegif' 
        , 'bmp' => 'imagebmp' 
    ); 
    $suffix = strtolower( array_pop(explode('.', $dstimage ) ) ); 
    if (!in_array($suffix, array_keys($arr)) ) { 
        echo "±£´æµÄÎļþÃû´íÎó"; 
        exit; 
    } else { 
        eval( $arr[$suffix] . '($dstimg, "'.$dstimage.'");' ); 
    } 
    imagejpeg($dstimg, $dstimage); 
    imagedestroy($dstimg); 
    imagedestroy($srcimg); 
}


function getcreatemethod( $file ) { 
    $arr = array( 
        '474946' => "imagecreatefromgif('$file')" 
        , 'FFD8FF' => "imagecreatefromjpeg('$file')" 
        , '424D' => "imagecreatefrombmp('$file')" 
        , '89504E' => "imagecreatefrompng('$file')" 
    ); 
    $fd = fopen( $file, "rb" ); 
    $data = fread( $fd, 3 ); 
    $data = str2hex( $data ); 
    if ( array_key_exists( $data, $arr ) ) { 
        return $arr[$data]; 
    } elseif ( array_key_exists( substr($data, 0, 4), $arr ) ) { 
        return $arr[substr($data, 0, 4)]; 
    } else { 
        return false; 
    } 
}

function str2hex( $str ) { 
    $ret = ""; 
    for( $i = 0; $i < strlen( $str ) ; $i++ ) { 
        $ret .= ord($str[$i]) >= 16 ? strval( dechex( ord($str[$i]) ) ) 
        : '0'. strval( dechex( ord($str[$i]) ) ); 
    } 
    return strtoupper( $ret ); 
}


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; 
    $BMP = unpack('Vheader_size/Vwidth/Vheight/vplanes/vbits_per_pixel'. 
        '/Vcompression/Vsize_bitmap/Vhoriz_resolution'. 
        '/Vvert_resolution/Vcolors_used/Vcolors_important', fread($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 
                return FALSE; 
            imagesetpixel($res,$X,$Y,$COLOR[1]); 
            $X++; 
            $P += $BMP['bytes_per_pixel']; 
        } 
        $Y--; 
        $P+=$BMP['decal']; 
    } 
    fclose($f1); 
    return $res; 
}

function imagebmp ($im, $fn = false) { 
    if (!$im) return false; 
    if ($fn === false) $fn = 'php://output'; 
    $f = fopen ($fn, "w"); 
    if (!$f) return false; 
    $biWidth = imagesx ($im); 
    $biHeight = imagesy ($im); 
    $biBPLine = $biWidth * 3; 
    $biStride = ($biBPLine + 3) & ~3; 
    $biSizeImage = $biStride * $biHeight; 
    $bfOffBits = 54; 
    $bfSize = $bfOffBits + $biSizeImage; 
    fwrite ($f, 'BM', 2); 
    fwrite ($f, pack ('VvvV', $bfSize, 0, 0, $bfOffBits)); 
    fwrite ($f, pack ('VVVvvVVVVVV', 40, $biWidth, $biHeight, 1, 24, 0, $biSizeImage, 0, 0, 0, 0)); 
    $numpad = $biStride - $biBPLine; 
    for ($y = $biHeight - 1; $y >= 0; --$y) 
    { 
        for ($x = 0; $x < $biWidth; ++$x) 
        { 
            $col = imagecolorat ($im, $x, $y); 
            fwrite ($f, pack ('V', $col), 3); 
        } 
        for ($i = 0; $i < $numpad; ++$i) 
            fwrite ($f, pack ('C', 0)); 
    } 
    fclose ($f); 
    return true; 
} 
?>