原因

最近在做網頁拖拽驗證碼的開源專案，需要在服務端生成圖片對應的可移動的色塊，但是網上的資源都是做縮圖，對整個圖片進行縮放的，所以自己動手，完成了對圖片進行裁剪小塊的工具

CODE

<?php

namespace  App\Libs;

/**
 * 2016-01-07 15:54:58
 * Lixiaoyu
 * 
 * mode 1 : 強制裁剪，生成圖片嚴格按照需要，不足放大，超過裁剪，圖片始終鋪滿
 * mode 2 : 和1類似，但不足的時候 不放大 會產生補白，可以用png消除。
 * mode 3 : 只縮放，不裁剪，保留全部圖片資訊，會產生補白，
 * mode 4 : 只縮放，不裁剪，保留全部圖片資訊，生成圖片大小為最終縮放後的圖片有效資訊的實際大小，不產生補白
 * 預設補白為白色，如果要使補白成透明畫素，請使用SaveAlpha()方法代替SaveImage()方法

 */
 

class ImageCrop{

    var $sImage;
    var $dImage;
    var $src_file;
    var $dst_file;
    var $src_width;
    var $src_height;
    var $src_ext;
    var $src_type;

    function __construct($src_file,$dst_file=''){
        $this->src_file=$src_file;
        $this->dst_file=$dst_file;
        $this
 
->LoadImage();
    }

    function SetSrcFile($src_file){
        $this->src_file=$src_file;
    }

    function SetDstFile($dst_file){
        $this->dst_file=$dst_file;
    }

    function LoadImage(){
        list($this->src_width, $this->src_height, $this->src_type) = getimagesize($this
 
->src_file);
        switch($this->src_type) {
            case IMAGETYPE_JPEG :
                $this->sImage=imagecreatefromjpeg($this->src_file);
                $this->ext='jpg';
                break;
            case IMAGETYPE_PNG :
                $this->sImage=imagecreatefrompng($this->src_file);
                $this->ext='png';
                break;
            case IMAGETYPE_GIF :
                $this->sImage=imagecreatefromgif($this->src_file);
                $this->ext='gif';
                break;
            default:
                exit();
        }
    }

    function SaveImage($fileName=''){
        $this->dst_file=$fileName ? $fileName : $this->dst_file;
        switch($this->src_type) {
            case IMAGETYPE_JPEG :
                imagejpeg($this->dImage,$this->dst_file,100);
                break;
            case IMAGETYPE_PNG :
                imagepng($this->dImage,$this->dst_file);
                break;
            case IMAGETYPE_GIF :
                imagegif($this->dImage,$this->dst_file);
                break;
            default:
                break;
        }
    }

    function OutImage(){
        switch($this->src_type) {
            case IMAGETYPE_JPEG :
                header('Content-type: image/jpeg');
                imagejpeg($this->dImage);
                break;
            case IMAGETYPE_PNG :
                header('Content-type: image/png');
                imagepng($this->dImage);
                break;
            case IMAGETYPE_GIF :
                header('Content-type: image/gif');
                imagegif($this->dImage);
                break;
            default:
                break;
        }
    }

    function SaveAlpha($fileName=''){
        $this->dst_file=$fileName ? $fileName . '.png' : $this->dst_file .'.png';
        imagesavealpha($this->dImage, true);
        imagepng($this->dImage,$this->dst_file);
    }

    function OutAlpha(){
        imagesavealpha($this->dImage, true);
        header('Content-type: image/png');
        imagepng($this->dImage);
    }

    function destory(){
        imagedestroy($this->sImage);
        imagedestroy($this->dImage);
    }

    function Crop($dst_width,$dst_height,$mode=1,$dst_file=''){
        if($dst_file) $this->dst_file=$dst_file;
        $this->dImage = imagecreatetruecolor($dst_width,$dst_height);

        $bg = imagecolorallocatealpha($this->dImage,255,255,255,127);
        imagefill($this->dImage, 0, 0, $bg);
        imagecolortransparent($this->dImage,$bg);



        $ratio_w=1.0 * $dst_width / $this->src_width;
        $ratio_h=1.0 * $dst_height / $this->src_height;
        $ratio=1.0;
        switch($mode){
            case 1:        // always crop
                if( ($ratio_w < 1 && $ratio_h < 1) || ($ratio_w > 1 && $ratio_h > 1)){
                    $ratio = $ratio_w < $ratio_h ? $ratio_h : $ratio_w;
                    $tmp_w = (int)($dst_width / $ratio);
                    $tmp_h = (int)($dst_height / $ratio);
                    $tmp_img=imagecreatetruecolor($tmp_w , $tmp_h);
                    $src_x = (int) (($this->src_width-$tmp_w)/2) ;
                    $src_y = (int) (($this->src_height-$tmp_h)/2) ;
                    imagecopy($tmp_img, $this->sImage, 0,0,$src_x,$src_y,$tmp_w,$tmp_h);
                    imagecopyresampled($this->dImage,$tmp_img,0,0,0,0,$dst_width,$dst_height,$tmp_w,$tmp_h);
                    imagedestroy($tmp_img);
                }else{
                    $ratio = $ratio_w < $ratio_h ? $ratio_h : $ratio_w;
                    $tmp_w = (int)($this->src_width * $ratio);
                    $tmp_h = (int)($this->src_height * $ratio);
                    $tmp_img=imagecreatetruecolor($tmp_w ,$tmp_h);
                    imagecopyresampled($tmp_img,$this->sImage,0,0,0,0,$tmp_w,$tmp_h,$this->src_width,$this->src_height);
                    $src_x = (int)($tmp_w - $dst_width) / 2 ;
                    $src_y = (int)($tmp_h - $dst_height) / 2 ;
                    imagecopy($this->dImage, $tmp_img, 0,0,$src_x,$src_y,$dst_width,$dst_height);
                    imagedestroy($tmp_img);
                }
                break;
            case 2:        // only small
                if($ratio_w < 1 && $ratio_h < 1){
                    $ratio = $ratio_w < $ratio_h ? $ratio_h : $ratio_w;
                    $tmp_w = (int)($dst_width / $ratio);
                    $tmp_h = (int)($dst_height / $ratio);
                    $tmp_img=imagecreatetruecolor($tmp_w , $tmp_h);
                    $src_x = (int) ($this->src_width-$tmp_w)/2 ;
                    $src_y = (int) ($this->src_height-$tmp_h)/2 ;
                    imagecopy($tmp_img, $this->sImage, 0,0,$src_x,$src_y,$tmp_w,$tmp_h);
                    imagecopyresampled($this->dImage,$tmp_img,0,0,0,0,$dst_width,$dst_height,$tmp_w,$tmp_h);
                    imagedestroy($tmp_img);
                }elseif($ratio_w > 1 && $ratio_h > 1){
                    $dst_x = (int) abs($dst_width - $this->src_width) / 2 ;
                    $dst_y = (int) abs($dst_height -$this->src_height) / 2;
                    imagecopy($this->dImage, $this->sImage,$dst_x,$dst_y,0,0,$this->src_width,$this->src_height);
                }else{
                    $src_x=0;$dst_x=0;$src_y=0;$dst_y=0;
                    if(($dst_width - $this->src_width) < 0){
                        $src_x = (int) ($this->src_width - $dst_width)/2;
                        $dst_x =0;
                    }else{
                        $src_x =0;
                        $dst_x = (int) ($dst_width - $this->src_width)/2;
                    }

                    if( ($dst_height -$this->src_height) < 0){
                        $src_y = (int) ($this->src_height - $dst_height)/2;
                        $dst_y = 0;
                    }else{
                        $src_y = 0;
                        $dst_y = (int) ($dst_height - $this->src_height)/2;
                    }
                    imagecopy($this->dImage, $this->sImage,$dst_x,$dst_y,$src_x,$src_y,$this->src_width,$this->src_height);
                }
                break;
            case 3:        // keep all image size and create need size
                if($ratio_w > 1 && $ratio_h > 1){
                    $dst_x = (int)(abs($dst_width - $this->src_width )/2) ;
                    $dst_y = (int)(abs($dst_height- $this->src_height)/2) ;
                    imagecopy($this->dImage, $this->sImage, $dst_x,$dst_y,0,0,$this->src_width,$this->src_height);
                }else{
                    $ratio = $ratio_w > $ratio_h ? $ratio_h : $ratio_w;
                    $tmp_w = (int)($this->src_width * $ratio);
                    $tmp_h = (int)($this->src_height * $ratio);
                    $tmp_img=imagecreatetruecolor($tmp_w ,$tmp_h);
                    imagecopyresampled($tmp_img,$this->sImage,0,0,0,0,$tmp_w,$tmp_h,$this->src_width,$this->src_height);
                    $dst_x = (int)(abs($tmp_w -$dst_width )/2) ;
                    $dst_y = (int)(abs($tmp_h -$dst_height)/2) ;
                    imagecopy($this->dImage, $tmp_img, $dst_x,$dst_y,0,0,$tmp_w,$tmp_h);
                    imagedestroy($tmp_img);
                }
                break;
            case 4:        // keep all image but create actually size
                if($ratio_w > 1 && $ratio_h > 1){
                    $this->dImage = imagecreatetruecolor($this->src_width,$this->src_height);
                    imagecopy($this->dImage, $this->sImage,0,0,0,0,$this->src_width,$this->src_height);
                }else{
                    $ratio = $ratio_w > $ratio_h ? $ratio_h : $ratio_w;
                    $tmp_w = (int)($this->src_width * $ratio);
                    $tmp_h = (int)($this->src_height * $ratio);
                    $this->dImage = imagecreatetruecolor($tmp_w ,$tmp_h);
                    imagecopyresampled($this->dImage,$this->sImage,0,0,0,0,$tmp_w,$tmp_h,$this->src_width,$this->src_height);
                }
                break;
        }
    }// end Crop


    /**
     *
     * 裁切方法
     * 2016-01-07 15:05:44
     * Lixiaoyu
     *
     * @param $dst_width 目標長
     * @param $dst_height  目標高
     * @param $dst_x   裁剪部分和原圖左側的距離
     * @param $dst_y   裁剪部分和原圖右側的距離
     * @param int $mode  模式
     * @param string $dst_file  目標檔案路徑
     */
    function Cut($dst_width,$dst_height,$dst_x,$dst_y,$dst_file='')
    {
        if ($dst_file) $this->dst_file = $dst_file;  //設定目標檔案位置
        $this->dImage = imagecreatetruecolor($dst_width, $dst_height); //建立了目標檔案的大小的畫布

        $bg = imagecolorallocatealpha($this->dImage, 255, 255, 255, 127); //給畫布分配顏色
        imagefill($this->dImage, 0, 0, $bg);     //給影象用顏色進行填充
        imagecolortransparent($this->dImage, $bg);  //背景定義成透明色

        $ratio_w = 1.0 * $dst_width / $this->src_width;  //橫向縮放的比例
        $ratio_h = 1.0 * $dst_height / $this->src_height;  //縱向縮放的比例

        //var_dump($this);


        //不進行縮放,直接對影象進行裁剪
        $ratio = 1.0;
        $tmp_w = (int)($dst_width / $ratio);
        $tmp_h = (int)($dst_height / $ratio);
        $tmp_img = imagecreatetruecolor($dst_width, $dst_height); //建立暫時儲存的畫布
        imagecopy($tmp_img, $this->sImage, 0,0,$dst_x,$dst_y,$dst_width,$dst_height);  //拷貝出影象的一部分,進行裁切
        imagecopyresampled($this->dImage,$tmp_img,0,0,0,0,$dst_width,$dst_height,$tmp_w,$tmp_h); //把暫時快取的圖片,放到目標檔案裡面
        imagedestroy($tmp_img);

    }
}
?>

Use

裁剪影象

$ic=new ImageCrop($pathToFile,'./pic/afterCrop'.time().'.jpg');
$ic->Cut(40,30,120,130);
$ic->SaveImage();
//$ic->SaveAlpha();將補白變成透明畫素儲存
$ic->destory();

實現效果

原圖

裁剪之後的圖

縮放影象

原圖

縮圖

重點難點

重點在於使用影象處理函式 imagecopy 和 imagecopyresampled

bool imagecopy ( resource dstim,resourcesrc_im , int dstx,intdst_y , int srcx,intsrc_y , int srcw,intsrc_h )
將 src_im 影象中座標從 src_x，src_y 開始，寬度為 src_w，高度為 src_h 的一部分拷貝到 dst_im 影象中座標為 dst_x 和 dst_y 的位置上。

參考資料