Questions about PHP generating thumbnail images

Problems with PHP generating thumbnail images
I think so ....
I set the thumbnail image size to be generated to 100*50

My original picture is 1000*600.

I want to have the original picture equal to the scale, horizontal or vertical center. Other places with white fill, do not know what I mean to express no

------Solution--------------------
Original W1 H1
New Figure W2 H2

If W1/H1 > W2/H2//low height after scaling
New Figure High H = h2/w2*w1
Offset y = (h2-h)/2 when vertically centered
x = 0
If W1/H1 < W2/H2//low width after scaling
New Figure W = w2/h2*h1
Offset at horizontal Center x = (x2-x)/2
y = 0


------Solution--------------------
Picture processing class for a CMS

PHP Code

 
  __construct ($targetfile, $cfg _thumb, $cfg _watermarktext, $photo _waterpos, $photo _diaphaneity, $photo _wheight, $photo    _wwidth, $cfg _watermarktype, $photo _marktrans, $trueMarkimg, $attach); }//Destructors function __construct ($targetfile, $cfg _thumb, $cfg _watermarktext, $photo _waterpos, $photo _diaphaneity, $ph Oto_wheight, $photo _wwidth, $cfg _watermarktype, $photo _marktrans, $trueMarkimg, $attach = Array ()) {$this->th        Umbstatus = $cfg _thumb;        $this->watermarktext = $cfg _watermarktext;        $this->watermarkstatus = $photo _waterpos;        $this->watermarkquality = $photo _marktrans;        $this->watermarkminwidth = $photo _wwidth;        $this->watermarkminheight = $photo _wheight;        $this->watermarktype = $cfg _watermarktype;        $this->watermarktrans = $photo _diaphaneity;        $this->animatedgif = 0;        $this->targetfile = $targetfile;        $this->attachinfo = @getimagesize ($targetfile);  $this->attach = $attach;      Switch ($this->attachinfo[' mime ') {case ' image/jpeg ': $this->imagecreatefrom Func = function_exists (' Imagecreatefromjpeg ')?                ' Imagecreatefromjpeg ': '; $this->imagefunc = function_exists (' imagejpeg ')?                ' imagejpeg ': ';            Break Case ' image/gif ': $this->imagecreatefromfunc = function_exists (' imagecreatefromgif ')?                ' Imagecreatefromgif ': '; $this->imagefunc = function_exists (' imagegif ')?                ' Imagegif ': ';            Break Case ' image/png ': $this->imagecreatefromfunc = function_exists (' imagecreatefrompng ')?                ' Imagecreatefrompng ': '; $this->imagefunc = function_exists (' imagepng ')?                ' Imagepng ': ';        Break }//a function of match type does not exist $this->attach[' size ' = Empty ($this->attach[' size ')?        @filesize ($targetfile): $this->attach[' size '; if ($this->attachinfo[' mime ') = = ' Image/gif '{$fp = fopen ($targetfile, ' RB ');            $targetfilecontent = Fread ($fp, $this->attach[' size ');            Fclose ($FP); $this->animatedgif = Strpos ($targetfilecontent, ' NETSCAPE2.0 ') = = = False?        0:1; }}/** * Generate thumbnails * * @access public * @param int $thumbwidth picture width * @param int $th Umbheight picture Height * @param int $preview preview * @return void */function thumb ($thumbwidth, $thumbhei        ght, $preview = 0) {$this->thumb_gd ($thumbwidth, $thumbheight, $preview); if ($this->thumbstatus = = 2 && $this->watermarkstatus) {$this->image ($this->targetfi            Le, $this->attach);        $this->attach[' size '] = filesize ($this->targetfile);     }}/** * Generate thumbnails using GD * * @access public * @param int $thumbwidth picture Width * @param int $thumbheight picture Height * @param int $preview Preview * @return void */function thumb_gd ($thumbwidth, $thumbheight, $preview = 0) {if ($this->thumbstatus && function_exists (' Imagecreatetruecolor ') && function_exists (' imagecopyresampled ') &&            Function_exists (' imagejpeg ')) {$imagecreatefromfunc = $this->imagecreatefromfunc; $imagefunc = $this->thumbstatus = = 1?            ' imagejpeg ': $this->imagefunc;            List ($imagewidth, $imageheight) = $this->attachinfo;                if (! $this->animatedgif && ($imagewidth >= $thumbwidth | | $imageheight >= $thumbheight)) {                $attach _photo = $imagecreatefromfunc ($this->targetfile);                $x _ratio = $thumbwidth/$imagewidth;                $y _ratio = $thumbheight/$imageheight; if (($x _ratio * $imageheight) < $thumbheight) {$thumb [' height '] = ceil ($x _ratio * $im                    Ageheight); $thumb [' width '] = $thumbwidTh                    } else {$thumb [' width '] = ceil ($y _ratio * $imagewidth);                $thumb [' height '] = $thumbheight; } $targetfile =! $preview? ($this->thumbstatus = = 1? $this->targetfile.                Thumb.jpg ': $this->targetfile): './watermark_tmp.jpg ';                $thumb _photo = Imagecreatetruecolor ($thumb [' width '], $thumb [' height ']); Imagecopyresampled ($thumb _photo, $attach _photo, 0, 0, 0, 0, $thumb [' width '], $thumb [' height '], $imagewidth, $                ImageHeight);  if ($this->attachinfo[' mime '] = = ' Image/jpeg ') {$imagefunc ($thumb _photo, $targetfile,                100);                } else {$imagefunc ($thumb _photo, $targetfile); } $this->attach[' thumb ' = $this->thumbstatus = = 1?            1:0; }}}}//end Class
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