如何在不保存图像的情况下调整远程图像的大小

您可以使用ImageMagick (http://php.net/manual/en/book.imagick.php)，假设您已经安装了它。

解决方案:

function crop( $url, $width, $height, $x = 0, $y = 0 )
{
    $file    = file_get_contents( $url );
    $imagick = new Imagick;
    $imagick->readImageBlob( $file );
    $imagick->cropImage( $width, $height, $x, $y );
    $base64 = base64_encode( $imagick->getImageBlob() );
    return "data:image/jpeg;base64," . $base64;
}

这需要一个URL，"裁剪区域"的宽度和高度，以及x - y参数，来设置"裁剪区域"左上角的位置。

data:image/jpeg;指定输出格式

我有一个类，但它有一些依赖关系，所以我将粘贴相关的比特，让你开始。对不起，我没有GIT安装后重做我的HD，所以例如有一个缺失的异常类依赖。我相信你可以把它整理出来，而且我已经有两年没用过它了。所以我不能保证一切正常。

 <?php
namespace Lib'Image;
/**
 * @author ArtisiticPhoenix
 * @package Lib
 * @subpackage Image
 *
 */
Class LibImage{
    const MODE_CROP = 'crop';
    const MODE_STRETCH = 'stretch';
    const MODE_SHRINK = 'shirnk';
    const MODE_FILL = 'fill';
    const POS_TOP = 1;
    const POS_BOTTOM = 2;
    const POS_LEFT = 4;
    const POS_RIGHT = 8;
    public $img_src = '';
    public $image = null;
    public $image_type = null;
    /**
     * 
     * @param string $src 
     */
    public function __construct($file_src=null, $string_src=null){
        if(!is_null($file_src)){
            $this->setImage($file_src);
        }
    }
    /**
     * is the image loaded
     * @return boolean
     */
    public function isLoaded(){
        return !is_null($this->image);  
    }
    /**
     * load an image file
     * @param filepath $file_src
     * @throws ImageException
     */
    public function setImage($file_src){
        if(!is_null($file_src)){
            if(!is_file($file_src)){
                throw new ImageException('[ '.$file_src.' ]', ImageException::ER_NO_FILE);
            }
            $this->img_src = $file_src;
            $this->image_type = exif_imagetype($this->img_src);
            switch($this->image_type)
            {
                case IMAGETYPE_GIF:
                    $this->image = imagecreatefromgif($file_src);
                break;
                case IMAGETYPE_JPEG:
                    $this->image = imagecreatefromjpeg($file_src);
                break;
                case IMAGETYPE_PNG:
                    $this->image = imagecreatefrompng($file_src);
                    imagealphablending($this->image, true); // setting alpha blending on
                    imagesavealpha($this->image, true); // save alphablending setting (important)
                break;
                case IMAGETYPE_WBMP:
                    $this->image = imagecreatefromwbmp($file_src);
                break;
                default:
                    throw new ImageException('', ImageException::ER_MIME);
            }
        }
    }
    /**
     * get the image height - y
     * @return number
     */
    public function height(){
        return imagesy($this->image);
    }
    /**
     * get the image width - x
     * @return number
     */
    public function width(){
        return imagesx($this->image);
    }
    /**
     * get the aspect of image
     * @return number
     */
    public function getAspect(){
        return $this->width() / $this->height();
    }
    /**
     * get the image info
     * @return array:
     */
    public function getInfo(){
        return $this->image_info;
    }
    //@todo
    public function calc_offset($src_width, $src_height, $dest_width, $dest_height, $location=0){

        if($location & self::POS_TOP){ //bitwise &
        }else if($location & self::POS_BOTTOM){
        }else{
            $centreY = round($dest_height / 2);
            $y = $centreY - $src_height / 2;
        }
        if($location & self::POS_LEFT){
        }else if($location & self::POS_RIGHT){
        }else{
            $centreX = round($dest_width / 2);
            $x = $centreX - $src_width / 2;
        }
        return array('x'=>$x, 'y'=>$y);
    }
    /**
     * get the greatest dimension
     * @return string
     */
    public function greaterDim(){
        if($this->width() > $this->height()){
            return 'width';
        }else if($this->width() < $this->height()){
            return 'height';
        }else{
            return 'equal';
        }
    }
    /**
     * get the image orientation
     * @return string
     */
    public function getOrientation(){
        $dim = $this->GreaterDim();
        if($dim == 'height'){
            return 'portrait';
        }else if($dim == 'width'){
            return 'landscape';
        }else{
            return 'equal';     
        }
    }
    ///transforms//////
    /**
     * fit the image in a box
     * @param number $width
     * @param number $height
     * @param string $mode
     */
    public function fitBox($width, $height, $mode=false, $position=32){
        switch ($mode){
            case self::MODE_CROP:
                //shrink the shortest dim to fit in the box - then center crop the exess
                if($this->width() <= $this->height() && $this->width() > $width){
                    $this->resizeToWidth($width);
                }else if($this->width() > $this->height() && $this->height() > $height){
                    $this->resizeToHeight($height);
                }else{
                    print_rr('TODO');
                }
                $this->cropTo($width, $height);
            break;
            case self::MODE_FILL:
                $this->fitBox($width, $height, self::MODE_SHRINK);
                $this->expandCanvaseTo($width, $height);
            break;
            case self::MODE_SHRINK:
                $this->resizeToHeight($height);
                //shrink to fit in the box bounds
                if($this->width() > $width){
                    $this->resizeToWidth($width);
                }   
            break;
            case self::MODE_STRETCH:
            default:
                //stretch the image to fit in the box bounds
                $this->resize($width, $height);
            break;
        }
    }
    /**
     * scale image by percent (eg. 100 - full size)
     * @param int $scale
     */
    function scale($scale) {
        $width = $this->width() * $scale / 100;
        $height = $this->height() * $scale / 100;
        $this->resize($width, $height);
    }
    /**
     * resize image to height
     * @param number $height
     */
    function resizeToHeight($height) {
        $ratio = $height / $this->height();
        $width = $this->width() * $ratio;
        $this->resize($width, $height);
    }
    /**
     * resize image to width
     * @param number $width
     */
    function resizeToWidth($width) {
        $ratio = $width / $this->width();
        $height = $this->height() * $ratio;
        $this->resize($width, $height);
    }
    /**
     * resize image by width and height (stretch)
     * @param number $width
     * @param number $height
     */
    function resize($width,$height) {
        $new_image = $this->createCanvas($width, $height);
        imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->width(), $this->height());
        $this->image = $new_image;
    } 
    /**
     * 
     * @param number $width
     * @param unknown $height
     * @return resource
     */
    function createCanvas($width, $height){
        $new_image = imagecreatetruecolor($width, $height);
        if($this->image_type==IMAGETYPE_PNG || $this->image_type==IMAGETYPE_GIF){
            imagealphablending($new_image, false);
            imagesavealpha($new_image, true);
            if($this->image_type==IMAGETYPE_GIF){
                $new_image = imagecreate($width, $height);
            }
        }
        $white = imagecolorallocate($new_image, 255, 255, 255);
        imagefill( $new_image, 0, 0, $white );
        return $new_image;
    }
    /**
     * 
     * @param int $dst_x - x-coordinate of destination point.
     * @param int $dst_y - y-coordinate of destination point.
     * @param int $src_x - x-coordinate of source point.
     * @param int $src_y - y-coordinate of source point.
     * @param number $width - Source width.
     * @param number $height - Source height.
     */
    function crop($dst_x, $dst_y, $src_x, $src_y, $width, $height){
        $new_image = $this->createCanvas($width, $height);
        imagecopy ( $new_image, $this->image, $dst_x, $dst_y, $src_x, $src_y, $width, $height );
        $this->image = $new_image;
    }
    /**
     * 
     * @param number $width
     * @param number $height
     * @param int $position - @todo
     */
    function cropTo($width, $height, $position=32){
        $centreX = round($this->width() / 2);
        $centreY = round($this->height() / 2);
        $x = $centreX - $width / 2;
        $y = $centreY - $height / 2;
        if ($x < 0) $x = 0;
        if ($y < 0) $y = 0;
        $this->crop(0, 0, $x, $y, $width, $height);
    }

    function expandCanvaseTo($width, $height, $position=32){
        $centreX = round($width / 2);
        $x = $centreX - $this->width() / 2;
        $centreY = round($height / 2);
        $y = $centreY - $this->height() / 2;
        if ($x < 0) $x = 0;
        if ($y < 0) $y = 0;
        $new_image = $this->createCanvas($width, $height);
        imagecopy ( $new_image, $this->image, $x, $y, 0, 0, $this->width(), $this->height() );
        $this->image = $new_image;
    }
    /**
     * //@todo test and update this
     * @param unknown $degrees
     * @param number $bg
     */
    function rotate($degrees, $bg=0){
        $this->image = imagerotate($this->image, $degrees, $bg);
        //imagecolortransparent($this->image, imagecolorallocate($this->image, 0, 0, 0));
    }
    /**
     * 
     * @param string $watermark_src - path to watermark image
     */
    function watermarkImage($watermark_src) {
        $WaterMark = new self($watermark_src);
        //make sure the watermark will always fit in the image confines
        if($this->width() < $WaterMark->width() || $this->height() < $WaterMark->height()){
            $WaterMark->fitBox($this->width(), $this->height(), self::MODE_SHRINK);
        }
        // Set the tile
        imagesettile($this->image, $WaterMark->image);
        // Make the image repeat
        imagefilledrectangle($this->image, 0, 0, $this->width(), $this->height(), IMG_COLOR_TILED);
    }
    //@todo http://us2.php.net/manual/en/function.imageflip.php

   /////////output////////////
   /**
    *  update old image file
    * @param number $res
    */
    function save($res=90){
        $this->Create($this->img_src, $res);
    }
    /**
     * save image with filename dest - or save over file
     * @param string $dest
     * @param number $res
     * @throws ImageException
     */
    function create($dest, $res=90){    
        switch($this->image_type){
            case IMAGETYPE_GIF:
                imagegif($this->image, $dest, $res);
            break;
            case IMAGETYPE_JPEG:
                imagejpeg($this->image, $dest, $res);
            break;
            case IMAGETYPE_PNG:
                $res = ceil($res*0.1); //convert from 0-100 to 1-10
                imagepng($this->image, $dest, $res);
            break;
            case IMAGETYPE_WBMP:
                imagewbmp($this->image, $dest, $res);
            break;
            default:
                throw new ImageException('', ImageException::ER_MIME);
        }
    }
    /**
     * render to browser
     * @param number $res
     * @throws ImageException
     */
    function render($res=90){   
        switch($this->image_type){
            case IMAGETYPE_GIF:
                header('Content-Type: image/gif');
                imagegif($this->image, null, $res);
            break;
            case IMAGETYPE_JPEG:
                header('Content-Type: image/jpg');
                imagejpeg($this->image, null, $res);
            break;
            case IMAGETYPE_PNG:
                header('Content-Type: image/png');
                $res = ceil($res*0.1); //convert from 0-100 to 1-10
                imagepng($this->image, null, $res);
            break;
            case IMAGETYPE_WBMP:
                header('Content-Type: image/bmp');
                imagewbmp($this->image, null, $res);
            break;
            default:
                throw new ImageException('', ImageException::ER_MIME);
        }
    }  
    /**
     * close image resorce
     */
    function __distruct(){
        imagedestroy($this->image);
    }
}

你会想要这样做，

 $Image = new 'Lib'Image'LibImage( 'image.jpg' );
 $Image->fitBox(300, 200, 'Lib'Image'LibImage::MODE_CROP );
 $Image->save();