Why does the upload image have a transparent channel and the image becomes black?

P.S. Change the image upload class original address: http://blog.csdn.net/a957651480/article/details/23124257

 Chk_err (-1); No incoming control name}else{$this->inputname = $inputName;} if (!empty ($allowType)) $this->allowtype = $allowType, if (!empty ($allowSize)) $this->allowsize = $allowSize; Empty ($saveDir)) $this->savedir = $saveDir, if (!empty ($isRename)) $this->isrename = $isRename;}    function is_uploaded () {if (Empty ($_files[$this->inputname][' name ')) {$this->chk_err (4); No files were uploaded}else{if (is_uploaded_file ($_files[$this->inputname][' tmp_name ')) {return true;}       else{$this->chk_err (-2); File Upload illegal}}}function chk_type () {if (!in_array ($_files[$this->inputname][' type '], $this->allowtype)) {$this-         >chk_err (-3); The uploaded file type is not allowed}else{return true;}}          function Chk_size () {if ($_files[$this->inputname][' size ') > $this->allowsize) {$this->chk_err (-4); The uploaded file is too large}else{return true;}} function move_uploaded () {//Move upload file if (! $this->is_uploaded ()) {return false;} if (! $this->chk_size ()) {return false;} if (! $this->chk_type ()) {return false;} Rename if ($this-> isrename) {$arrTmp = PathInfo ($_files[$this->inputname][' name '); $extension = Strtolower ($arrTmp [' extension ']); $file _newname = $this->filename; Rename new file}else{$file _newname = $_files[$this->inputname][' name '];}    if (!file_exists ($this->savedir)) {//Determine if the Save directory exists mkdir ($this->savedir,0777,true); Create a Save directory}//move File $result = Move_uploaded_file ($_files[$this->inputname][' tmp_name '), $this->savedir. " /". $file _newname), if ($result) {$path = $this->savepath = $this->savedir." /". $file the successful save path to the _newname;//file return $path;} else{$this->chk_err ($_files[$this->inputname][' error ');}} Error message function Chk_err ($errID) {$this->errid = $errID; switch ($this->errid) {case-4: $this->errmsg = ' Only images within 1M can be uploaded | [Return] '; break;case-3: $this->errmsg = ' This is not a picture | [Return] '; break;case-2: $this->errmsg = ' file Upload not valid | [Return] '; break;case-1: $this->errmsg = ' No control name passed in | [Return] '; Break;case 1: $this->errmsg = ' The uploaded file exceeds the maximum value of upload_max_filesize set in PHP.ini | [Return] '; Break;case 2: $this->errmsg = ' upload fileThe size exceeds the value specified by the MAX_FILE_SIZE option in the HTML form | [Return] '; Break;case 3: $this->errmsg = ' file only partially uploaded | [Return] '; Break;case 4: $this->errmsg = ' Please select a picture | [Return] '; break;default:break;} return false;}  function get_errmsg () {echo $this->errmsg; Output error message}/** +----------------------------------------------------------* Get image information * +----------------- -----------------------------------------* @static * @access public +---------------------------------------- ------------------* @param string $image image file name +----------------------------------------------------------*        @return Mixed +----------------------------------------------------------*/function Getimageinfo ($img) {        $imageInfo = getimagesize ($img);            if ($imageInfo!== false) {$imageType = Strtolower (substr (Image_type_to_extension ($imageInfo [2]), 1));            $imageSize = FileSize ($img); $info = Array ("width" = = $imageInfo [0], "height" => $imageInfo [1], "type" = = $imageType, "size" + = $imageSize, "mime" = = $ima            Geinfo[' MIME '],);        return $info;        }else {return false; }}/** +----------------------------------------------------------* Generate thumbnails +------------------------------- ---------------------------* @static * @access public +------------------------------------------------------ ----* @param string $image original * @param string $type image format * @param string $thumbname thumbnail filename * @param stri ng $maxWidth Width * @param string $maxHeight Height * @param string $position thumbnail Save directory * @param boolean $interlace Enable Interlaced * @param boolean $is _save whether to keep the original +----------------------------------------------------------* @return void +----------------------------------------------------------*/function thumb ($image, $is _save=true, $suofa ng=0, $type = ", $maxWidth =500, $maxHeight =500,$Interlace=true) {//Get the original information $info = $this->getimageinfo ($image);            if ($info!== false) {$srcWidth = $info [' width '];            $srcHeight = $info [' height '];            $type = Empty ($type)? $info [' type ']: $type; $type = Strtolower ($type); $interlace = $interlace?            1:0;            Unset ($info);                if ($suofang ==1) {$width = $srcWidth;            $height = $srcHeight; } else {$scale = min ($maxWidth/$srcWidth, $maxHeight/$srcHeight);//Calculate scaling if ($scale >=1                    {//above the original size no longer abbreviated $width = $srcWidth;                $height = $srcHeight;  }else{//thumbnail size $width = (int) ($srcWidth * $scale);//147 $height = (int) ($srcHeight * $scale);//199}}//Load the original $createFun = ' Imagecreatefrom '. ($type = = ' jpg '? ')            JPEG ': $type); $srCIMG = $createFun ($image); Create thumbnails if ($type! = ' gif ' && function_exists (' Imagecreatetruecolor ')) $THUMBIMG = Imagecre            Atetruecolor ($width, $height);            else $thumbImg = Imagecreate ($width, $height); Copy Picture if (Function_exists ("imagecopyresampled")) imagecopyresampled ($thumbImg, $srcImg, 0, 0, 0            , 0, $width, $height, $srcWidth, $srcHeight);            else imagecopyresized ($thumbImg, $srcImg, 0, 0, 0, 0, $width, $height, $srcWidth, $srcHeight); if (' gif ' = = $type | | ' png ' = = $type) {//imagealphablending ($thumbImg, false);//cancels the default process-color mode//imagesavealpha ($thumbIm  G,true)//set to save complete alpha channel information $background _color = Imagecolorallocate ($thumbImg, 0,255,0);  Assign a green imagecolortransparent ($THUMBIMG, $background _color); Set to Transparent color, if the line is commented out the output green graph}//JPEG graphics set interlaced if (' jpg ' = = $type | | ' jpeg ' = = $type) Imageinterlace ($THUMBIMG, $interlace);            $gray =imagecolorallocate ($THUMBIMG, 255,0,0);            Imagestring ($THUMBIMG, 2,5,5, "thinkphp", $gray); Generate Picture $imageFun = ' imagejpeg '; $length = strlen ("00.").            $type) * ( -1); $_type = substr ($image, -4); $length = ($type! = $_type? $length + 1: $length); Crop if ($suofang = = 1) {//$thumbname = Substr_replace ($image, "01."). $type, $length);//Big head like $THUMBNAME02 = Substr_replace ($image, '. gif ',-8);//small head//$imageFun ($THUMBIMG, $thumbname 01,100)                ; $imageFun ($THUMBIMG, $thumbname 02,100);                $THUMBIMG: Imagecreatetruecolor (190,195); Imagecopyresampled ($THUMBIMG, $THUMBIMG, 0,0,$_post[' x '],$_post[' y '],190,195,$_post[' W '],$_post[' h ']);                THUMBIMG02 = Imagecreatetruecolor ($this->imgsize, $this->imgsize); Imagecopyresampled ($THUMBIMG, $THUMBIMG, 0,0,$_post[' x '],$_post[' y '), $this->imgsize, $this->imgsize,$_ post[' W '],$_post[' h ']);//$imageFun ($THUMBIMG, $THUMBName01,100), $imageFun ($THUMBIMG, $thumbname 02,100), unlink ($image);//imagedestroy ($THUMBIMG); Imagedestroy ($ THUMBIMG02); Imagedestroy ($THUMBIMG); Imagedestroy ($SRCIMG); return Array (/* ' big ' = $thumbname, */' small ' = = $ THUMBNAME02);//Returns an array}else{if ($is _save = = False) containing the size of the head path {//thumbnail overlay original, thumbnail path or original path $imagefun ($THUMBIMG, $image, 100); }else{$thumbname $image;//thumbnail and original image exist simultaneously, $imageFun ($THUMBIMG, $thumbname 03,100); Imagedestroy ($THUMBIMG);    Imagedestroy ($SRCIMG); return $thumbname 03;//Returns the path of the thumbnail, string}}} to false; }}

Reply to discussion (solution)

Uploading does not change the picture, you can paste the picture here
For GD2 thumbnails should be imagecreatetruecolor, imagecopyresampled
If you have a transparent color, you also need to imagecolortransparent

Put a picture on it and see

Put a picture on it and see

is a plain picture with a transparent channel ...

Put a picture on it and see

is a plain picture with a transparent channel ...

How did you upload the call, I just tried to put down your picture, I finished this pass no problem

The pictures produced by Imagecreate and Imagecreatetruecolor are black (note: not transparent)
Your picture is transparent, and naturally the background is revealed.
Which means the picture is on a black background.
So the scaled picture also needs to set the transparent color

$url = ' http://img.bbs.csdn.net/upload/201404/15/1397545309_839045.gif '; $sm = imagecreatefromstring (file_get_ Contents ($url)); $DM = Imagecreatetruecolor (Imagesx ($SM), Imagesy ($SM));//$DM = Imagecreate (Imagesx ($SM), Imagesy ($SM ); $c = Imagecolorallocate ($DM, 1, 1); Imagefill ($DM, 0, 0, $c); Imagecolortransparent ($DM, $c); Imagecopyresampled ($ DM, $SM, 0, 0, 0, 0, Imagesx ($DM), Imagesy ($DM), Imagesx ($SM), Imagesy ($SM)), Imagegif ($DM);

I solved it myself. Thank you, I didn't fill it with Imagefill beforehand.

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