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：
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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)
}
});
}
});
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PHP的片段：
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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;
}
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