本文使用php实现的图片缩略图，支持jpg,jpeg,gif,png,bmp图片格式，支持按原图片的比例进行缩放，可以选择在图片缩放的过程中是否需要对图片进行裁切，加入了图片质量控制，可以实现缩略图片质量最高化，需要的朋友可以参考下本段代码。

本段代码实现功能有这些：

支持jpg,jpeg,gif,png,bmp图片格式，支持按原图片的比例进行缩放，可以选择在图片缩放的过程中是否需要对图片进行裁切，加入了图片质量控制，可以实现缩略图片质量最高化。

完整类的代码如下：

1. <?php
2. /**
3. * 功能：php生成缩略图片的类
4. */
5. class ResizeImage{
6. public $type;//图片类型
7. public $width;//实际宽度
8. public $height;//实际高度
9. public $resize_width;//改变后的宽度
10. public $resize_height;//改变后的高度
11. public $cut;//是否裁图
12. public $srcimg;//源图象
13. public $dstimg;//目标图象地址
14. public $im;//临时创建的图象
15. public $quality;//图片质量
16. function resizeimage($img,$wid,$hei,$c,$dstpath,$quality=100){
17. $this->srcimg=$img;
18. $this->resize_width=$wid;
19. $this->resize_height=$hei;
20. $this->cut=$c;
21. $this->quality=$quality;
22. $this->type=strtolower(substr(strrchr($this->srcimg,'.'),1));//图片的类型
23. $this->initi_img();//初始化图象
24. $this -> dst_img($dstpath);//目标图象地址
25. @$this->width=imagesx($this->im);
26. @$this->height=imagesy($this->im);
27. $this->newimg();//生成图象
28. @ImageDestroy($this->im);
29. }
30. function newimg(){
31. $resize_ratio=($this->resize_width)/($this->resize_height);//改变后的图象的比例
32. @$ratio=($this->width)/($this->height);//实际图象的比例
33. if(($this->cut)=='1'){//裁图
34. if($img_func==='imagepng'&&(str_replace('.','',PHP_VERSION)>=512)){ //针对php版本大于5.12参数变化后的处理情况
35. $quality=9;
36. }
37. if($ratio>=$resize_ratio){//高度优先
38. $newimg=imagecreatetruecolor($this->resize_width,$this->resize_height);
39. imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,$this->resize_height,(($this->height)*$resize_ratio),$this->height);
40. imagejpeg($newimg,$this->dstimg,$this->quality);
41. }
42. if($ratio<$resize_ratio){//宽度优先
43. $newimg=imagecreatetruecolor($this->resize_width,$this->resize_height);
44. imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,$this->resize_height,$this->width,(($this->width)/$resize_ratio));
45. imagejpeg($newimg,$this->dstimg,$this->quality);
46. }
47. }else{//不裁图
48. if($ratio>=$resize_ratio){
49. $newimg=imagecreatetruecolor($this->resize_width,($this->resize_width)/$ratio);
50. imagecopyresampled($newimg,$this->im,0,0,0,0,$this->resize_width,($this->resize_width)/$ratio,$this->width,$this->height);
51. imagejpeg($newimg,$this->dstimg,$this->quality);
52. }
53. if($ratio<$resize_ratio){
54. @$newimg=imagecreatetruecolor(($this->resize_height)*$ratio,$this->resize_height);
55. @imagecopyresampled($newimg,$this->im,0,0,0,0,($this->resize_height)*$ratio,$this->resize_height,$this->width,$this->height);
56. @imagejpeg($newimg,$this->dstimg,$this->quality);
57. }
58. }
59. }
60. function initi_img(){//初始化图象
61. if($this->type=='jpg' || $this->type=='jpeg'){
62. $this->im=imagecreatefromjpeg($this->srcimg);
63. }
64. if($this->type=='gif'){
65. $this->im=imagecreatefromgif($this->srcimg);
66. }
67. if($this->type=='png'){
68. $this->im=imagecreatefrompng($this->srcimg);
69. }
70. if($this->type=='wbm'){
71. @$this->im=imagecreatefromwbmp($this->srcimg);
72. }
73. if($this->type=='bmp'){
74. $this->im=$this->ImageCreateFromBMP($this->srcimg);
75. }
76. }
77. function dst_img($dstpath){//图象目标地址
78. $full_length=strlen($this->srcimg);
79. $type_length=strlen($this->type);
80. $name_length=$full_length-$type_length;
81. $name=substr($this->srcimg,0,$name_length-1);
82. $this->dstimg=$dstpath;
83. //echo $this->dstimg;
84. }
85. function ImageCreateFromBMP($filename){ //自定义函数处理bmp图片
86. if(!$f1=fopen($filename,"rb"))returnFALSE;
87. $FILE=unpack("vfile_type/Vfile_size/Vreserved/Vbitmap_offset",fread($f1,14));
88. if($FILE['file_type']!=19778)returnFALSE;
89. $BMP=unpack('Vheader_size/Vwidth/Vheight/vplanes/vbits_per_pixel'.
90. '/Vcompression/Vsize_bitmap/Vhoriz_resolution'.
91. '/Vvert_resolution/Vcolors_used/Vcolors_important',fread($f1,40));
92. $BMP['colors']=pow(2,$BMP['bits_per_pixel']);
93. if($BMP['size_bitmap']==0)$BMP['size_bitmap']=$FILE['file_size']-$FILE['bitmap_offset'];
94. $BMP['bytes_per_pixel']=$BMP['bits_per_pixel']/8;
95. $BMP['bytes_per_pixel2']=ceil($BMP['bytes_per_pixel']);
96. $BMP['decal']=($BMP['width']*$BMP['bytes_per_pixel']/4);
97. $BMP['decal']-=floor($BMP['width']*$BMP['bytes_per_pixel']/4);
98. $BMP['decal']=4-(4*$BMP['decal']);
99. if($BMP['decal']==4)$BMP['decal']=0;
100. $PALETTE=array();
101. if($BMP['colors']<16777216)
102. {
103. $PALETTE=unpack('V'.$BMP['colors'],fread($f1,$BMP['colors']*4));
104. }
105. $IMG=fread($f1,$BMP['size_bitmap']);
106. $VIDE=chr(0);
107. $res=imagecreatetruecolor($BMP['width'],$BMP['height']);
108. $P=0;
109. $Y=$BMP['height']-1;
110. while($Y>=0)
111. {
112. $X=0;
113. while($X<$BMP['width'])
114. {
115. if($BMP['bits_per_pixel']==24)
116. $COLOR=unpack("V",substr($IMG,$P,3).$VIDE);
117. elseif($BMP['bits_per_pixel']==16)
118. {
119. $COLOR=unpack("n",substr($IMG,$P,2));
120. $COLOR[1]=$PALETTE[$COLOR[1]+1];
121. }
122. elseif($BMP['bits_per_pixel']==8)
123. {
124. $COLOR=unpack("n",$VIDE.substr($IMG,$P,1));
125. $COLOR[1]=$PALETTE[$COLOR[1]+1];
126. }
127. elseif($BMP['bits_per_pixel']==4)
128. {
129. $COLOR=unpack("n",$VIDE.substr($IMG,floor($P),1));
130. if(($P*2)%2==0)$COLOR[1]=($COLOR[1]>>4);else$COLOR[1]=($COLOR[1]&0x0F);
131. $COLOR[1]=$PALETTE[$COLOR[1]+1];
132. }
133. elseif($BMP['bits_per_pixel']==1)
134. {
135. $COLOR=unpack("n",$VIDE.substr($IMG,floor($P),1));
136. if(($P*8)%8==0)$COLOR[1]=$COLOR[1]>>7;
137. elseif(($P*8)%8==1)$COLOR[1]=($COLOR[1]&0x40)>>6;
138. elseif(($P*8)%8==2)$COLOR[1]=($COLOR[1]&0x20)>>5;
139. elseif(($P*8)%8==3)$COLOR[1]=($COLOR[1]&0x10)>>4;
140. elseif(($P*8)%8==4)$COLOR[1]=($COLOR[1]&0x8)>>3;
141. elseif(($P*8)%8==5)$COLOR[1]=($COLOR[1]&0x4)>>2;
142. elseif(($P*8)%8==6)$COLOR[1]=($COLOR[1]&0x2)>>1;
143. elseif(($P*8)%8==7)$COLOR[1]=($COLOR[1]&0x1);
144. $COLOR[1]=$PALETTE[$COLOR[1]+1];
145. }
146. else
147. returnFALSE;
148. imagesetpixel($res,$X,$Y,$COLOR[1]);
149. $X++;
150. $P+=$BMP['bytes_per_pixel'];
151. }
152. $Y--;
153. $P+=$BMP['decal'];
154. }
155. fclose($f1);
156. return$res;
157. }
158. }
159. ?>

使用方法很简单代码如下：

$resizeimage=new ResizeImage('upload/abc.bmp', '120', '90', '0', 'upload/xabc.bmp');

以上代码是小编给大家分享的php实现图片缩略图的方法，希望对大家有所帮助！