【PHP缩略图类】手机照片不能生成缩略图问题以及解决方案
【本文原创，谢绝转载】
这几天做了手机上传照片并裁出缩略图的接口的测试，发现不管怎么，生成的缩略图都是一片漆黑。:-(
然后就把这个缩略图类单拿出来进行测试，发现只要是手机拍出来的照片都不能进行缩略图的处理。。。。
经过群里的请教，发现问题可能是出现在文件的类型的判断上，因为png图片自带一个透明的图层，导致不能直接转换成jpg的文件，而手机排出的照片扩展名是jpg.
所以，得出的结论是手机拍出的是jpg扩展名的png图片。
由于扩展名是可以随意修改的，不是很能保证文件的信息的准确性，所以我们采用了 getimagesize 函数进行文件类型的获取。
//获取真实的图片类型 list($width, $height, $type, $attr) = getimagesize($this->sur_file); switch($type) { case 1 : $img_type = 'gif'; break; case 2 : $img_type = 'jpeg'; break; case 3 : $img_type = 'png'; break; case 15 : $img_type = 'wbmp'; break; default : return false; } 三、生成缩略图类
下面把修改后的生成缩略图的类贴出来，供大家指正~
/** * php生成缩略图类 * 修改者 点点细雨 * 文章出处 ： http://blog.csdn.net/diandianxiyu_geek * 2014-07-23 解决了图片类型不能正常识别的问题 */class thumb { public $sur_file; //读取的原图片 public $des_file; //生成目标图片 public $tem_file; //临时图片 public $tag; //缩略标签 0,默认,按固定的高宽生成 1,按比列或固定最大长度生成 -1,按某个宽度或某个高度缩小 public $resize_width; //$tag为0时,目标文件宽 public $resize_height; //$tag为0时,目标文件高 public $sca_max; //$tag为1时,1时为最大长度(高或宽之中的最大值) public $type; //图片类型 public $width; //原图片宽 public $height; //原图片高 public $size; //原图大小 //构造函数 public function __construct($surpic, $reswid, $reshei, $despic, $mark, $scamax) { $this->sur_file = $surpic; $this->resize_width = $reswid; $this->resize_height = $reshei; $this->tag = $mark; $this->sca_max = $scamax; list($width, $height, $type, $attr) = getimagesize($this->sur_file); switch ($type) { case 1 : $img_type = 'gif'; break; case 2 : $img_type = 'jpeg'; break; case 3 : $img_type = 'png'; break; case 15 : $img_type = 'wbmp'; break; default : return false; } $this->type = $img_type; //获取图片类型 $this->init_img(); //初始化图片 $this->des_file = $despic; //目标图片地址 $this->width = $width; $this->height = $height; $this->size = filesize($surpic); $this->new_img(); imagedestroy($this->tem_file); } //图片初始化函数 private function init_img() { if ($this->type == 'jpeg') { $this->tem_file = imagecreatefromjpeg($this->sur_file); } elseif ($this->type == 'jpg') { $this->tem_file = imagecreatefromjpeg($this->sur_file); } elseif ($this->type == 'gif') { $this->tem_file = imagecreatefromgif($this->sur_file); } elseif ($this->type == 'png') { $this->tem_file = imagecreatefrompng($this->sur_file); } elseif ($this->type == 'bmp') { $this->tem_file = imagecreatefrombmp($this->sur_file); //bmp.php中包含 } } //图片生成函数 private function new_img() { $ratio = ($this->width) / ($this->height); //原图比例 $resize_ratio = ($this->resize_width) / ($this->resize_height); //缩略后比例 $newimg = imagecreatetruecolor($this->resize_width, $this->resize_height); //生成新图片 imagealphablending($newimg, false); //这里很重要,意思是不合并颜色,直接用$img图像颜色替换,包括透明色; imagesavealpha($newimg, true); if ($this->tag == 0) { //按固定高宽截取缩略图 $newimg = imagecreatetruecolor($this->resize_width, $this->resize_height); //生成新图片 if ($ratio >= $resize_ratio) {//即等比例下,缩略图的高比原图长,因此高不变 imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, $this->resize_width, $this->resize_height, (($this->height) * $resize_ratio), $this->height); } elseif ($ratio tem_file, 0, 0, 0, 0, $this->resize_width, $this->resize_height, $this->width, (($this->width) / $resize_ratio)); } } elseif ($this->tag == 1) { //按固定比例或最大长度缩小 if ($this->sca_max width) * ($this->sca_max)), (($this->height) * ($this->sca_max))); //生成新图片 imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, (($this->width) * ($this->sca_max)), (($this->height) * ($this->sca_max)), $this->width, $this->height); } elseif ($this->sca_max > 1) { //按某个最大长度缩小 if ($ratio >= 1) { //宽比高长 $newimg = imagecreatetruecolor($this->sca_max, ($this->sca_max / $ratio)); //生成新图片 imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, $this->sca_max, ($this->sca_max / $ratio), $this->width, $this->height); } else { $newimg = imagecreatetruecolor(($this->sca_max * $ratio), $this->sca_max); //生成新图片 imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, ($this->sca_max * $ratio), $this->sca_max, $this->width, $this->height); } } } elseif ($this->tag == -1) { //按某个宽度或某个高度缩小 if ($resize_ratio >= 1) {//新高小于新宽,则图片按新宽度缩小 $newimg = imagecreatetruecolor($this->resize_width, ($this->resize_width / $ratio)); //生成新图片 imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, $this->resize_width, ($this->resize_width / $ratio), $this->width, $this->height); } elseif ($resize_ratio resize_height * $ratio), $this->resize_height); //生成新图片 imagecopyresampled($newimg, $this->tem_file, 0, 0, 0, 0, ($this->resize_height * $ratio), $this->resize_height, $this->width, $this->height); } } //输出新图片 if ($this->type == 'jpeg' || $this->type == 'jpg') { imagejpeg($newimg, $this->des_file); } elseif ($this->type == 'gif') { imagegif($newimg, $this->des_file); } elseif ($this->type == 'png') { imagepng($newimg, $this->des_file); } elseif ($this->type == 'bmp') { imagebmp($newimg, $this->des_file); //bmp.php中包含 } }#function new_img() end}
