原因

最近在做网页拖拽验证码的开源项目，需要在服务端生成图片对应的可移动的色块，但是网上的资源都是做缩略图，对整个图片进行缩放的，所以自己动手，完成了对图片进行裁剪小块的工具

CODE

<?php

namespace  App\Libs;

/**
 * 2016-01-07 15:54:58
 * Lixiaoyu
 * 
 * mode 1 : 强制裁剪，生成图片严格按照需要，不足放大，超过裁剪，图片始终铺满
 * mode 2 : 和1类似，但不足的时候 不放大 会产生补白，可以用png消除。
 * mode 3 : 只缩放，不裁剪，保留全部图片信息，会产生补白，
 * mode 4 : 只缩放，不裁剪，保留全部图片信息，生成图片大小为最终缩放后的图片有效信息的实际大小，不产生补白
 * 默认补白为白色，如果要使补白成透明像素，请使用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 目标长
     * @param $dst_height  目标高
     * @param $dst_x   裁剪部分和原图左侧的距离
     * @param $dst_y   裁剪部分和原图右侧的距离
     * @param int $mode  模式
     * @param string $dst_file  目标文件路径
     */
    function Cut($dst_width,$dst_height,$dst_x,$dst_y,$dst_file='')
    {
        if ($dst_file) $this->dst_file = $dst_file;  //设置目标文件位置
        $this->dImage = imagecreatetruecolor($dst_width, $dst_height); //创建了目标文件的大小的画布

        $bg = imagecolorallocatealpha($this->dImage, 255, 255, 255, 127); //给画布分配颜色
        imagefill($this->dImage, 0, 0, $bg);     //给图像用颜色进行填充
        imagecolortransparent($this->dImage, $bg);  //背景定义成透明色

        $ratio_w = 1.0 * $dst_width / $this->src_width;  //横向缩放的比例
        $ratio_h = 1.0 * $dst_height / $this->src_height;  //纵向缩放的比例

        //var_dump($this);


        //不进行缩放,直接对图像进行裁剪
        $ratio = 1.0;
        $tmp_w = (int)($dst_width / $ratio);
        $tmp_h = (int)($dst_height / $ratio);
        $tmp_img = imagecreatetruecolor($dst_width, $dst_height); //创建暂时保存的画布
        imagecopy($tmp_img, $this->sImage, 0,0,$dst_x,$dst_y,$dst_width,$dst_height);  //拷贝出图像的一部分,进行裁切
        imagecopyresampled($this->dImage,$tmp_img,0,0,0,0,$dst_width,$dst_height,$tmp_w,$tmp_h); //把暂时缓存的图片,放到目标文件里面
        imagedestroy($tmp_img);

    }
}
?>

Use

裁剪图像

$ic=new ImageCrop($pathToFile,'./pic/afterCrop'.time().'.jpg');
$ic->Cut(40,30,120,130);
$ic->SaveImage();
//$ic->SaveAlpha();将补白变成透明像素保存
$ic->destory();

实现效果

原图

裁剪之后的图

缩放图像

原图

缩略图

重点难点

重点在于使用图像处理函数 imagecopy 和 imagecopyresampled

bool imagecopy ( resource dstim,resourcesrc_im , int dstx,intdst_y , int srcx,intsrc_y , int srcw,intsrc_h )
将 src_im 图像中坐标从 src_x，src_y 开始，宽度为 src_w，高度为 src_h 的一部分拷贝到 dst_im 图像中坐标为 dst_x 和 dst_y 的位置上。

参考资料

• http://www.php.net/manual/zh/function.imagecopy.php
• http://php.net/manual/zh/function.imagecopyresampled.php