PHP5:图像缩小及格式转换CLASS

<?
/**
*
* 对图像进行缩小，也可对png,gif,jpeg,wbmp格式的图像进行转换
* 需要GD库的支持才可以，若要进行gif图像的输出需要GD2.0.28或更高版本才支持(或* gif的动画转了之后动画变成静画，不知为什么!
*
* @date 2004.08.16
* @author zhouxh#im.ac.cn
*
*/
class ResizeImage {
 
const ResizeImageInfo = "本类对图像进行缩小，也可对png,wbmp格式的图像进行转换";
 
//设置目标图像的宽和高
private $height = 100;
private $width = 100;
 
//源图像文件和目标图像文件，若只是输出至浏览器则目标图像文件可不设置
private $sourceFile = '';
private $dstFile = '';
 
//图像类型“image/gif、image/jpeg、image/png...”
private $imgType;
 
//源图像句柄和目标图像句柄
private $sim;
private $dim;
 
//是否保存图像，用public void saveFlag(boolean $flag)方法设置
private $saveFlag = true;
 
function __construct() {
if (!function_exists('imagecreate')) {
throw new Exception('你的系统不支持GD库');
}
}
 
function __toString() {
return ReSizeImage::ResizeImageInfo;
}
 
//设置目标图像的宽
public function setWidth($width) {
if ($width <= 0) {
throw new Exception('目标图像宽度不能小于0');
return ;
}
$this->width = $width;
}
 
//设置目标图像的高
public function setHeight($height) {
if ($height <= 0) {
throw new Exception('目标图像高度不能小于0');
return ;
}
$this->height = $height;
}
 
//设置源图像文件
public function setSourceFile($file) {
if (!file_exists($file)) {
throw new Exception('源图像文件不存在');
return ;
}
$this->sourceFile = $file;
}
 
//设置目标图像文件
public function setDstFile($file) {
$this->dstFile = $file;
}
 
//设置是否生成新文件
public function saveFile($flag) {
$this->saveFlag = (boolean)$flag;
}
 
//执行绘图操作，$quality参数表示生成图像的效果，数字越高，效果越好，不过仅用于jpeg类型的图像
public function draw($quality = 95) {
$sourceImgInfo = @getimagesize($this->sourceFile);
if (!is_array($sourceImgInfo)) {
throw new Exception('源图像文件不存在');
return ;
}
switch($sourceImgInfo[2]){
case 1:
$this->imgType="image/gif";
$this->sim = imagecreatefromgif($this->sourceFile);
break;
case 2:
$this->imgType="image/jpeg";
$this->sim = imagecreatefromjpeg($this->sourceFile);
break;
case 3:
$this->imgType="image/png";
$this->sim = imagecreatefrompng($this->sourceFile);
break;
case 15:
$this->imgType="image/wbmp";
$this->sim = imagecreatefromwbmp($this->sourceFile);
break;
default:
return '不支持的图像格式';
break;
}
 
//设置目标图像的实际宽和高
$dstWidth = $sourceWidth = $sourceImgInfo[0];
$dstHeight = $sourceHeight = $sourceImgInfo[1];
 
if ($sourceHeight > $this->height && $sourceWidth > $this->width) {
if ($sourceHeight > $sourceWidth) {
$zoom = $this->height / $sourceHeight;
$dstHeight = $this->height;
$dstWidth = $sourceWidth * $zoom;
} else {
$zoom = $this->width / $sourceWidth;
$dstWidth = $this->width;
$dstHeight = $sourceHeight * $zoom;
}
}
 
//建立目标图像的句柄
$this->dim = @imagecreatetruecolor($dstWidth,$dstHeight) or imagecreate($dstWidth,$dstHeight);
 
//将真彩色图像转换为调色板图像
imagetruecolortopalette($this->sim,false,256);
 
//根据源图像颜色的总数并把它分配到目标图像上
$palsize = ImageColorsTotal($this->sim);
for ($i = 0; $i<$palsize; $i++) {
$colors = ImageColorsForIndex($this->sim,$i);
ImageColorAllocate($this->dim,$colors['red'],$colors['green'],$colors['blue']);
}
 
//进行图像的缩放
imagecopyresampled($this->dim,$this->sim,$dstWidth,$dstHeight,$sourceWidth,$sourceHeight);
 
//生成新的目标图像
if ($this->saveFlag) {
$imgExt = substr($this->dstFile,strrpos($this->dstFile,'.') + 1);
switch(strtolower($imgExt)){
case 'gif':
if (!function_exists('imagegif')) {
throw new Exception('你的GD库不支持gif图像的输出');
return ;
}
imagegif($this->dim,$this->dstFile);
break;
case 'jpeg':
case 'jpg':
imagejpeg($this->dim,$this->dstFile,$quality);
break;
case 'png':
imagepng($this->dim,$this->dstFile);
break;
case 'wbmp':
imagewbmp($this->dim,$this->dstFile);
break;
default:
return '目标图像文件为空或者格式不对，无法进行保存';
break;
}
 
//直接输出目标图像至浏览器
} else {
header ("Content-type: " . $this->imgType);
switch($sourceImgInfo[2]){
case 1:
imagegif($this->dim);
break;
case 2:
imagejpeg($this->dim,'',$quality);
break;
case 3:
imagepng($this->dim);
break;
case 15:
imagewbmp($this->dim);
break;
default:
return '不支持的图像格式';
break;
}
}
return ;
}
 
function __destruct() {
@ImageDestroy($this->sim);
@ImageDestroy($this->dim);
}
}
?>

例子１：缩小图像后直接输出至浏览器
$obj = new ReSizeImage();
$obj->setSourceFile('win.png');
$obj->saveFile(false);
$obj->setWidth(250);
$obj->setHeight(250);
$obj->draw();

例子２：缩小图像后保存新图像文件为“new.png”
$obj = new ReSizeImage();
$obj->setSourceFile('win.png');
$obj->setDstFile('new.png');
$obj->setWidth(250);
$obj->setHeight(250);
$obj->draw();

例子３：缩小图像后保存新图像文件为“new.jpg”，并设置其quality值为“100”
$obj = new ReSizeImage();
$obj->setSourceFile('win.png');
$obj->setDstFile('new.jpg');
$obj->setWidth(250);
$obj->setHeight(250);
$obj->draw(100);

例子４：捕捉程序中的异常
try {
$obj = new ReSizeImage();
$obj->setSourceFile('no.png');
$obj->saveFile(false);
$obj->setWidth(250);
$obj->setHeight(250);
$obj->draw();
} catch (Exception $ex) {
echo $ex;
}