PHP图像复制透明背景

$input = imagecreatefrompng('image.png');
$output = imagecreatetruecolor(50, 50);
imagecopy($output, $input, 4,0, 8,8, 8,8);
imagecopy... etc.
header('Content-Type: image/png');
imagepng($output);

设置给定图像的透明颜色。

int imagecolortransparent ( resource $image [, int $color ] )

链接在这里

由于PHP函数imagecopymerge不与Alpha通道一起工作，您将想要使用本页imagecopymerge_alpha的第一条评论中的函数:http://php.net/manual/en/function.imagecopymerge.php

只需将透明图像作为基础，并将其与您需要的图像合并在一起。

我已经试过了，它在我的一个项目中工作得很好。

没有一个解决方案对我有效，它总是将源图像上的透明像素转换为目标图像上的黑色。将imagecopy/imagecopymerge/imagecopymerge_alpha更改为imagecopyresample，并传递相同的宽度和高度两次。

    //Create destination image.
    $png = imagecreatetruecolor(1024, 1024);
    imagealphablending($png, false);
    imagesavealpha($png, true);
    //Make destination image be all transparent.
    $color = imagecolorallocatealpha($png, 0, 0, 0, 127); //127 means completely transparent.
    imagefill($png, 0, 0, $color);
    //Load source image.
    $png2 = imagecreatefrompng($sourceurl);
    imagealphablending($png2, false);
    imagesavealpha($png2, true);
    $sizex = imagesx($png2);
    $sizey = imagesy($png2);
    //Copy to destination and save to file.
    imagecopyresampled( $png, $png2, 
    0, 0,
    0, 0, 
    $sizex, $sizey, 
    $sizex, $sizey);
    imagepng($png, "result.png");

imagealphablending($input, true);
imagesavealpha($input, true);
imagealphablending($output, true);
imagesavealpha($output, true);

全部归功于:http://consistentcoder.com/combine-a-transparent-png-image-on-top-of-another-image-with-php

下面的代码将把前景图像叠加到背景图像上，同时保留叠加的透明度:

//set the source image (foreground)
$sourceImage = 'table.png';
//set the destination image (background)
$destImage = 'create-a-surreal-head-of-tree-photo-manipulation.jpg';
//get the size of the source image, needed for imagecopy()
list($srcWidth, $srcHeight) = getimagesize($sourceImage);
//create a new image from the source image
$src = imagecreatefrompng($sourceImage);
//create a new image from the destination image
$dest = imagecreatefromjpeg($destImage);
//set the x and y positions of the source image on top of the destination image
$src_xPosition = 75; //75 pixels from the left
$src_yPosition = 50; //50 pixels from the top
//set the x and y positions of the source image to be copied to the destination image
$src_cropXposition = 0; //do not crop at the side
$src_cropYposition = 0; //do not crop on the top
//merge the source and destination images
imagecopy($dest,$src,$src_xPosition,$src_yPosition,
          $src_cropXposition,$src_cropYposition,
          $srcWidth,$srcHeight);
//output the merged images to a file
/*
 * '100' is an optional parameter,
 * it represents the quality of the image to be created,
 * if not set, the default is about '75'
 */
imagejpeg($dest,
    'combine-a-transparent-png-image-on-top-of-another-image-with-php-01.jpg',
    100);
//destroy the source image
imagedestroy($src);
//destroy the destination image
imagedestroy($dest);

或者

int imagesavealpha($img,true);

http://www.php.net/manual/en/function.imagesavealpha.php