php gd等比例缩放压缩图片函数

本文实例为大家分享了php gd等比例缩放压缩图片函数，供大家参考，具体内容如下

<?php  /**   * desription 判断是否gif动画   * @param sting $image_file图片路径   * @return boolean t 是 f 否   */  function check_gifcartoon($image_file){    $fp = fopen($image_file,'rb');    $image_head = fread($fp,1024);    fclose($fp);    return preg_match("/".chr(0x21).chr(0xff).chr(0x0b).'NETSCAPE2.0'."/",$image_head)?false:true;  }  /**  * desription 压缩图片  * @param sting $imgsrc 图片路径  * @param string $imgdst 压缩后保存路径  */  function compressed_image($imgsrc,$imgdst){    list($width,$height,$type)=getimagesize($imgsrc);    $new_width = ($width>600?600:$width)*0.9;    $new_height =($height>600?600:$height)*0.9;    switch($type){      case 1:        $giftype=check_gifcartoon($imgsrc);        if($giftype){          header('Content-Type:image/gif');          $image_wp=imagecreatetruecolor($new_width, $new_height);          $image = imagecreatefromgif($imgsrc);          imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);          //75代表的是质量、压缩图片容量大小          imagejpeg($image_wp, $imgdst,75);          imagedestroy($image_wp);        }        break;      case 2:        header('Content-Type:image/jpeg');        $image_wp=imagecreatetruecolor($new_width, $new_height);        $image = imagecreatefromjpeg($imgsrc);        imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);        //75代表的是质量、压缩图片容量大小        imagejpeg($image_wp, $imgdst,75);        imagedestroy($image_wp);        break;      case 3:        header('Content-Type:image/png');        $image_wp=imagecreatetruecolor($new_width, $new_height);        $image = imagecreatefrompng($imgsrc);        imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);        //75代表的是质量、压缩图片容量大小        imagejpeg($image_wp, $imgdst,75);        imagedestroy($image_wp);        break;    }  }

php and gd 函数参考表
gd_info 取得当前安装的 GD 库的信息
getimagesize 取得图像大小
getimagesizefromstring Get the size of an image from a string
image_type_to_extension 取得图像类型的文件后缀
image_type_to_mime_type 取得 getimagesize，exif_read_data，exif_thumbnail，exif_imagetype 所返回的图像类型的 MIME 类型
image2wbmp 以 WBMP 格式将图像输出到浏览器或文件
imageaffine Return an image containing the affine tramsformed src image, using an optional clipping area
imageaffinematrixconcat Concat two matrices (as in doing many ops in one go)
imageaffinematrixget Return an image containing the affine tramsformed src image, using an optional clipping area
imagealphablending 设定图像的混色模式