PHP 图片裁切

PHP CLASS TO CREATE IMAGE THUMBANILS

Some years ago, I wrote a PHP class to create image thumbnails because I needed it for a project. There were needed certain things that I could not able to find in other PHP classes, and I decided to create one with my specific needs. Today, after some improvements and fixes to perfect it, I have decided to share it with anyone that wants to use it.

Features of this class:

• It is possible to work with the main image formats (jpg, png, and gif).
• It is possible to resize images setting a width or a height and maintaining the original proportion.
• It is possible to crop the images to a custom size maintaining its original proportion (it is also possible to chose the cropping position).
• It is possible to store the resulting image in the server.
• Is is possible to show the image in the browser on the fly.
• It is possible to keep the alpha channel of PNG and GIFs images.

This class needs the GD library installed in the server (included in PHP from version 4.3)

  1 class Thumb {
  2
  3     private $image;
  4     private $type;
  5     private $mime;
  6     private $width;
  7     private $height;
  8
  9     //---读取图像的方法
 10     public function loadImage($name) {
 11
 12         //---存储图像尺寸
 13         $info = getimagesize($name);
 14
 15         $this->width = $info[0];
 16         $this->height = $info[1];
 17         $this->type = $info[2];
 18         $this->mime = $info['mime'];
 19
 20         //---根据原始格式创建新图像
 21         switch($this->type){
 22
 23             case IMAGETYPE_JPEG:
 24                 $this->image = imagecreatefromjpeg($name);
 25             break;
 26
 27             case IMAGETYPE_GIF:
 28                 $this->image = imagecreatefromgif($name);
 29             break;
 30
 31             case IMAGETYPE_PNG:
 32                 $this->image = imagecreatefrompng($name);
 33             break;
 34
 35             default:
 36                 trigger_error('It is not possible to create a thumbnail using the specified format', E_USER_ERROR);
 37
 38         }
 39
 40     }
 41
 42     //---存储图像的方法
 43     public function save($name, $quality = 100, $type = false) {
 44
 45         //---如果格式不存在，请选择原始图像的格式

 46         $type = ($type) ? $type : $this->type;

 47         //---使用正确的格式存储图像
 48         switch($type){
 49
 50             case IMAGETYPE_JPEG:
 51                 imagejpeg($this->image, $name . image_type_to_extension($type), $quality);
 52             break;
 53
 54             case IMAGETYPE_GIF:
 55                 imagegif($this->image, $name . image_type_to_extension($type));
 56             break;
 57
 58             case IMAGETYPE_PNG:
 59                 $pngquality = floor($quality / 100 * 9);
 60                 imagepng($this->image, $name . image_type_to_extension($type), $pngquality);
 61             break;
 62             default:
 63                 trigger_error('The specified image format is not correct', E_USER_ERROR);
 64         }
 65     }
 66     //---即时显示图像的方法
 67     public function show($type = false, $base64 = false) {
 68
 69         //---如果格式不存在，请选择原始图像的格式
 70         $type = ($type) ? $type : $this->type;
 71         if($base64) ob_start();
 72
 73         //---使用正确的格式显示图像
 74         switch($type){
 75             case IMAGETYPE_JPEG:
 76                 imagejpeg($this->image);
 77             break;
 78
 79             case IMAGETYPE_GIF:
 80                 imagegif($this->image);
 81             break;
 82
 83             case IMAGETYPE_PNG:
 84                 $this->prepareImage($this->image);
 85                 imagepng($this->image);
 86             break;
 87
 88             default:
 89                 trigger_error('The specified image format is not correct', E_USER_ERROR);
 90                 exit;
 91         }
 92
 93         if($base64) {
 94             $data = ob_get_contents();
 95             ob_end_clean ();
 96             return 'data:' . $this->mime . ';base64,' . base64_encode($data);
 97         }
 98
 99     }
100
101     //---按比例调整图像大小的方法
102     public function resize($value, $prop){
103
104         //---确定resize属性
105         $prop_value = ($prop == 'width') ? $this->width : $this->height;
106         $prop_versus = ($prop == 'width') ? $this->height : $this->width;
107
108         //---Determine the opposite resize property
109         $pcent = $value / $prop_value;
110         $value_versus = $prop_versus * $pcent;
111
112         //---使用resize属性创建图像
113         $image = ($prop == 'width') ? imagecreatetruecolor($value, $value_versus) : imagecreatetruecolor($value_versus, $value);
114
115         //---Treat the image
116         if($this->type == IMAGETYPE_GIF || $this->type == IMAGETYPE_PNG) $this->prepareImage($image);
117
118         //---制作一张考虑了resize属性的图像副本
119         switch($prop){
120             case 'width':
121                 imagecopyresampled($image, $this->image, 0, 0, 0, 0, $value, $value_versus, $this->width, $this->height);
122             break;
123
124             default:
125                 imagecopyresampled($image, $this->image, 0, 0, 0, 0, $value_versus, $value, $this->width, $this->height);
126         }
127
128         //---Update the image and its dimensions
129         $this->width = imagesx($image);
130         $this->height = imagesy($image);
131         $this->image = $image;
132     }
133
134     //---Method to extract a portion of the image maintaining its proportion
135     public function crop($cwidth, $cheight, $pos = 'center') {
136
137         $pcent = min($this->width / $cwidth, $this->height / $cheight);
138         $bigw = (int) ($pcent * $cwidth);
139         $bigh = (int) ($pcent * $cheight);
140
141         //---Create the image
142         $image = imagecreatetruecolor($cwidth, $cheight);
143
144         //---Treat the image
145         if($this->type == IMAGETYPE_GIF || $this->type == IMAGETYPE_PNG) $this->prepareImage($image);
146
147         //---Depending of the crop position
148         switch($pos){
149
150             case 'left':
151                 imagecopyresampled($image, $this->image, 0, 0, 0, abs(($this->height - $bigh) / 2), $cwidth, $cheight, $bigw, $bigh);
152             break;
153
154             case 'right':
155                 imagecopyresampled($image, $this->image, 0, 0, $this->width - $bigw, abs(($this->height - $bigh) / 2), $cwidth, $cheight, $bigw, $bigh);
156             break;
157
158             case 'top':
159                 imagecopyresampled($image, $this->image, 0, 0, abs(($this->width - $bigw) / 2), 0, $cwidth, $cheight, $bigw, $bigh);
160             break;
161
162             case 'bottom':
163                 imagecopyresampled($image, $this->image, 0, 0, abs(($this->width - $bigw) / 2), $this->height - $bigh, $cwidth, $cheight, $bigw, $bigh);
164             break;
165
166             default:
167                 imagecopyresampled($image, $this->image, 0, 0, abs(($bigw - $this->width) / 2), abs(($bigh - $this->height) / 2), $cwidth, $cheight, $bigw, $bigh);
168         }
169         $this->width = $cwidth;
170         $this->height = $cheight;
171         $this->image = $image;
172     }
173     //---Private method to treat the images before show them
174     private function prepareImage($image){
175         //---Depending on the image type
176         switch($this->type){
177             case IMAGETYPE_GIF:
178                 $background = imagecolorallocate($image, 0, 0, 0);
179                 imagecolortransparent($image, $background);
180             break;
181
182             case IMAGETYPE_PNG:
183                 imagealphablending($image, FALSE);
184                 imagesavealpha($image, TRUE);
185             break;
186         }
187     }
188 }

Public methods
//Reads the image from the specified path loadImage(string $name)
$name	Image path
//Stores the image in the specified path save(string $name [, int $quality = 100] [, int $type = false])
$name	Image path
$quality	Image quality with a value between 0 and 100
$type	Image type defined by a constant IMAGETYPE_XXX (IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF). It is optional, if it is not sent, the original format will be used
// Shows the image directly on the page or returns a base64 representation of it show([int $type = false] [,boolean $base64 = false])
$type	Image type defined by a constant IMAGETYPE_XXX (IMAGETYPE_JPEG, IMAGETYPE_PNG, IMAGETYPE_GIF). It is optional, if it is not sent, the original format will be used
$base64	Specifies if the image flow should be printed on the page or should be returned as a base64.
//Resizes the image maintaining its proprtion resize(int $value, string $reference)
$value	The value of width or height that should be used to resize the image
$reference	String that defines if the image should be resized taking into account the with or the height (possible values: ‘width’ or ‘height’)
//Crops the image creating a thumbnail of it crop(int $width, int $height [, string $position = 'center'])
$width	Width of the thumbnail
$height	Height of the thumbnail
$position	The position from which the thumbnail should be extracted (possible values: ‘top’, ‘right’, ‘bottom’, ‘left’ or ‘center’)

效果图: