PHP imagecopy with transparent background

I use this code to create an image from another png image, the background is black by default. My question is how to set a transparent background?

$input = imagecreatefrompng('image.png');
$output = imagecreatetruecolor(50, 50);

imagecopy($output, $input, 4,0, 8,8, 8,8);
imagecopy... etc.
开发者_运维百科
header('Content-Type: image/png');
imagepng($output);

Is there a easy way of doing this? Thanks

Sets the transparent color in the given image.

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

Here's the link

Since the PHP function imagecopymerge doesn't work with the Alpha channel, you'll want to use the function from the first comment on this page imagecopymerge_alpha: http://php.net/manual/en/function.imagecopymerge.php

Just have the transparent image as the base and merge it together with the image you need.

I've tried it out and it works fine for a project of mine.

None of the solutions worked for me, it would always convert transparent pixels on the source image to black on the destination image. What worked was changing imagecopy/imagecopymerge/imagecopymerge_alpha to imagecopyresampled and just passing the same width and height twice.

    //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);

Full credit goes to: http://consistentcoder.com/combine-a-transparent-png-image-on-top-of-another-image-with-php

The following code will overlay the foreground image onto the background image while preserving the transparency of the overlay:

//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);

Or propably

int imagesavealpha($img,true);

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