php实现图片压缩功能

简述：

使用php的GD库可以将图片按固定宽高或者等比例压缩，主要利用的函数是：

imagecopyresampled：将一张图片中的一块区域复制到另一张图片上

等比例压缩

/*** [compressImg description]* @param  string  $src     源图片* @param  integer $percent 压缩比例* @return [type]           [description]*/public function compressImg($src = '', $percent = 1){list($width, $height, $type, $attr) = getimagesize($src);$type = image_type_to_extension($type, false);$fun         = "imagecreatefrom" . $type;$image 		 = $fun($src);$new_width   = $width * $percent;$new_height  = $height * $percent;$thump = imagecreatetruecolor($new_width, $new_height);//将原图复制到另一张图片上，并且按照一定比例压缩imagecopyresampled($thump, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);imagedestroy($image);$image = $thump;// 1、浏览器直接输出header('Content-Type: image/' . $type);$funcs = "image" . $type;$funcs($thump);// 2、保存到对应路径$path = 'save.'.$type;$funcs = "image" . $type;$funcs($thump, $path);}

按固定宽高压缩

/*** [compressImgWH description]* @param  string $src        源图片* @param  string $new_width  压缩后宽度* @param  string $new_height 压缩后高度* @return [type]             [description]*/public function compressImgWH($src = '', $new_width='', $new_height=''){list($width, $height, $type, $attr) = getimagesize($src);$type = image_type_to_extension($type, false);$fun = "imagecreatefrom" . $type;$image = $fun($src);$thump = imagecreatetruecolor($new_width, $new_height);// 处理透明背景图片变成黑色的问题if(strtolower($type)=='png'){imageantialias($thump, true);$color = imagecolorallocate($thump, 255, 255, 255);imagecolortransparent($thump, $color);imagefill($thump, 0, 0, $color);}//将原图复制到其他图片上，并且按照一定宽高压缩imagecopyresampled($thump, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);imagedestroy($image);// 1、浏览器直接输出header('Content-Type: image/' . $type);$funcs = "image" . $type;$funcs($thump);// 2、保存到对应路径$path = 'save.'.$type;$funcs = "image" . $type;$funcs($thump, $path);}

功能演示：

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