Create a transparent png file using PHP

To 1)imagecreatefrompng('test.png') tries to open the file test.png which then can be edited with GD functions.

To 2)To enable saving of the alpha channel imagesavealpha($img, true); is used.The following code creates a 200x200px sized transparent image by enabling alpha saving and filling it with transparency.

<?php$img = imagecreatetruecolor(200, 200);imagesavealpha($img, true);$color = imagecolorallocatealpha($img, 0, 0, 0, 127);imagefill($img, 0, 0, $color);imagepng($img, 'test.png');

Take a look at:

• imagecolorallocatealpha
• imagefill

An example function copies transparent PNG files:

    <?php    function copyTransparent($src, $output)    {        $dimensions = getimagesize($src);        $x = $dimensions[0];        $y = $dimensions[1];        $im = imagecreatetruecolor($x,$y);         $src_ = imagecreatefrompng($src);         // Prepare alpha channel for transparent background        $alpha_channel = imagecolorallocatealpha($im, 0, 0, 0, 127);         imagecolortransparent($im, $alpha_channel);         // Fill image        imagefill($im, 0, 0, $alpha_channel);         // Copy from other        imagecopy($im,$src_, 0, 0, 0, 0, $x, $y);         // Save transparency        imagesavealpha($im,true);         // Save PNG        imagepng($im,$output,9);         imagedestroy($im);     }    $png = 'test.png';    copyTransparent($png,"png.png");    ?>

1) You can create a new png file without any existing one.2) You get a black color image because you use imagecreatetruecolor();. It creates a highest quality image with a black background. As you need a lowest quality image use imagecreate();

<?php$tt_image = imagecreate( 100, 50 ); /* width, height */$background = imagecolorallocatealpha( $tt_image, 0, 0, 255, 127 ); /* In RGB colors- (Red, Green, Blue, Transparency ) */header( "Content-type: image/png" );imagepng( $tt_image );imagecolordeallocate( $background );imagedestroy( $tt_image );?>

You can read more in this article: How to Create an Image Using PHP