使用 PHP GD 将一张图像与另一张图像屏蔽

Question

请看这个问题：PHP GD Use one image to mask another image, including transparency - 这里的规则是让用户创建新问题而不是重新访问旧问题并寻求支持

我一直在使用这个脚本来启用透明遮罩 - （可能的）区别在于源图像具有透明度，但似乎下面的代码仅在输入 PNG 没有透明度时才有效。有人可以看看我是否做错了什么？

我在下面尝试做的事情： 1. 获取 $source 图像 2.调整大小并在本地保存为pjg.png，保持透明度（这工作正常） 3. 用另一个 PNG 遮罩生成的图像。

信息：

• image.png 具有透明度。
• mask1.png 是黑色背景上的白色椭圆，没有透明度

• 最后保存的图像有黑色，此时它应该始终保持透明。

  <?php
  $data       = file_get_contents('assets/img/image.png');
  $source     = imagecreatefromstring( $data);
  
  
  // Set the percentage resize
  
  $percent = 0.5;
  
  // Get new dimensions
  list($width, $height) = getimagesize('assets/img/image.png');
  $new_width = $width * $percent;
  $new_height = $height * $percent;
  
  $image_p = imagecreatetruecolor($new_width, $new_height);
  imagealphablending($image_p, false);
  imagesavealpha( $image_p, true );
  
  imagecopyresampled($image_p, $source, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
  
  imagepng($image_p, "assets/img/pjg.png");
  
  $mask_id = 1;
  
  
  create_mask( $image_p, $mask_id ); 
  
  
  function create_mask( &$picture, $mask_id) {
  // Image masking using PHP
  // https://stackoverflow.com/questions/7203160/php-gd-use-one-image-to-mask-another-image-including-transparency
  
  $mask = imagecreatefrompng( 'assets/img/masks/mask'.$mask_id.'.png' );   // The mask is a white-on-black png
  
  
  
  // 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, 0, 0, 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 ) );
          $alpha = 127 - floor( $alpha[ 'red' ] / 2 );
          $color = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) );
          imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, $color[ 'red' ], $color[ 'green' ], $color[ 'blue' ], $alpha ) );
      }
  }
  
  $salt = random_string('alnum', 8); // Another function generating a string, not important
  $now = time();
  $new_filename = $now."_".$salt .".png";
  
  // Save it Locally using a unique name
  imagepng($newPicture, "assets/img/uploads/cropped/".$new_filename);
  
  
  // Copy back to original picture
  imagedestroy( $picture );
  $picture = $newPicture;
  
  }
  

如果有人能指出为什么输出图像没有保持其透明度，那么里面会有一杯不错的冰镇啤酒。

谢谢！

PJG

Answer 1

我已经解决了。原始脚本没有检查源图像的透明度。下面的脚本检查源图像的像素透明度，并采取相应措施。以下脚本在 PNG 图像上执行 shap 遮罩，并保持源图像的透明度。

<?php
$data       = file_get_contents('assets/img/image.png');
$source     = imagecreatefromstring( $data);


// Set the percentage resize

$percent = 0.5;

// Get new dimensions
list($width, $height) = getimagesize('assets/img/image.png');
$new_width = $width * $percent;
$new_height = $height * $percent;

$image_p = imagecreatetruecolor($new_width, $new_height);
imagealphablending($image_p, false);
imagesavealpha( $image_p, true );

imagecopyresampled($image_p, $source, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

imagepng($image_p, "assets/img/pjg.png");

$mask_id = 1;


create_mask( $image_p, $mask_id ); 


function create_mask( &$picture, $mask_id) {
// Image masking using PHP
// http://stackoverflow.com/questions/7203160/php-gd-use-one-image-to-mask-another-image-including-transparency

$mask = imagecreatefrompng( 'assets/img/masks/mask'.$mask_id.'.png' );   // The mask is a white-on-black png



// 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, 0, 0, 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 ) );

            if(($alpha['red'] == 0) && ($alpha['green'] == 0) && ($alpha['blue'] == 0) && ($alpha['alpha'] == 0))
            {
                // It's a black part of the mask
                imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, 0, 0, 0, 127 ) ); // Stick a black, but totally transparent, pixel in.
            }
            else
            {

                // Check the alpha state of the corresponding pixel of the image we're dealing with.    
                $alphaSource = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) );

                if(($alphaSource['alpha'] == 127))
                {
                    imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, 0, 0, 0, 127 ) ); // Stick a black, but totally transparent, pixel in.
                } 
                else
                {
                    $color = imagecolorsforindex( $picture, imagecolorat( $picture, $x, $y ) );
                    imagesetpixel( $newPicture, $x, $y, imagecolorallocatealpha( $newPicture, $color[ 'red' ], $color[ 'green' ], $color[ 'blue' ], $color['alpha'] ) ); // Stick the pixel from the source image in
                }


            }
    }
}

$salt = random_string('alnum', 8); // Another function generating a string, not important
$now = time();
$new_filename = $now."_".$salt .".png";

// Save it Locally using a unique name
imagepng($newPicture, "assets/img/uploads/cropped/".$new_filename);


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

}
?>

为阅读干杯——看来我以后要给自己买杯啤酒了 :)

PG