php+js 裁剪任意形状图片 ，类似css mask

最近做到相关的项目，由于项目使用html2canvas，但是不支持css mask属性，故，利用php后台来裁剪。

准备两张图片，一张是镂空PNG图案，一张是任意纯色图片。

便能够在纯色图片上裁剪出镂空的图案为PNG文件。

见下图。

首先两张PNG图片：

生成图片

JS片段：

   html2canvas($(".head1pic"), {
                                    onrendered: function(canvas) { 
                                        url = canvas.toDataURL("image/png", 1.0);
                                        sourcePic = "assets/images/demo.png";
                                        maskPic = "assets/images/jinmao.png";
                                        cropPicName = "cropDog1";
                                        // ajax php截图
                                        $.ajax({
                                            type: 'post',
                                            url: 'getpicture',
                                            data: {
                                                "sourcePic": sourcePic,
                                                "maskPic": maskPic,
                                                "cropPicName": cropPicName
                                            },
                                            success: function(data) {
                                                $(".page2Bg")[0].setAttribute("src", "assets/images/crop/cropDog1.png"); 
                                            },
                                            error: function(data) {
                                                console.log(data)
                                            }
                                        });
                                    }
                                });

PHP的片段：

 public function actionGetpicture()
    {   
         $request = Yii::$app->request;
        $sourcePic=$request->post('sourcePic');
        $maskPic=$request->post('maskPic'); 
        $cropPicName=$request->post('cropPicName'); 

        //  $sourcePic="http://bings.local.com/bi_ngs2_2/assets/images/yinpian1/page2Bg4.png";
        // $maskPic="http://bings.local.com/bi_ngs2_2/assets/images/jinmao.png";
        $source = imagecreatefrompng( $sourcePic );
        $mask = imagecreatefrompng( $maskPic); 
        // Apply mask to source
        // imagealphamask( $source, $mask );
        $this->imagealphamask ($source, $mask );
        // Output
        header( "Content-type: image/png"); 
        // 生成截取后的图片并保存在本地
        imagepng( $source,"assets/images/crop/".$cropPicName.".png" );
        //销毁图片内存
        imagedestroy($source);
           
   }
 
    public function imagealphamask( &$picture, $mask ) {
        // Get sizes and set up new picture
        $xSize = imagesx( $picture );
        $ySize = imagesy( $picture );
        $newPicture = imagecreatetruecolor( $xSize, $ySize );
        imagesavealpha( $newPicture, true );
        imagefill( $newPicture, 0, 0, imagecolorallocatealpha( $newPicture, 100, 100, 0, 127 ) );

        // Resize mask if necessary
        // if( $xSize != imagesx( $mask ) || $ySize != imagesy( $mask ) ) {
        //     $tempPic = imagecreatetruecolor( $xSize, $ySize );
        //     imagecopyresampled( $tempPic, $mask, 0, 0, 0, 0, $xSize, $ySize, imagesx( $mask ), imagesy( $mask ) );
        //     imagedestroy( $mask );
        //     $mask = $tempPic;
        // }

        // Perform pixel-based alpha map application
        for( $x = 0; $x < $xSize; $x++ ) {
            for( $y = 0; $y < $ySize; $y++ ) {
                $alpha = imagecolorsforindex( $mask, imagecolorat( $mask, $x, $y ) );
                //small mod to extract alpha, if using a black(transparent) and white
                //mask file instead change the following line back to Jules's original:
                // $alpha = 127 - floor($alpha['black'] / 2);
                //or a white(transparent) and black mask file:
                // $alpha = floor($alpha['black'] / 2);
                $alpha = $alpha['alpha'];
                $color = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) );
                //preserve alpha by comparing the two values
                if ($color['alpha'] > $alpha)
                    $alpha = $color['alpha'];
                //kill data for fully transparent pixels
                if ($alpha == 127) {
                    $color['red'] = 0;
                    $color['blue'] = 0;
                    $color['green'] = 0;
                }
                imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, $color[ 'red' ], $color[ 'green' ], $color[ 'blue' ], $alpha ) );
            }
        }

        // Copy back to original picture
        imagedestroy( $picture );
        $picture = $newPicture;
    }