Why does imagecreatefrompng() Produce a Black Background Instead of a Transparent Area?

imagecreatefrompng() Producing Black Background Instead of Transparent Area?

In PHP, the imagecreatefrompng() function is commonly used to work with PNG images. However, it has been observed that when using this function, PNG transparency may be converted into a solid black color.

To resolve this issue, the following steps can be implemented after creating a new canvas using imagecreatetruecolor():

1. Allocate a Black Color: Assign a black color to an integer variable using the imagecolorallocate() function.
2. Remove Black from Transparency: Utilize the imagecolortransparent() function to set black as the transparent color, effectively making it invisible.
3. Disable Alpha Blending: Use imagealphablending() with a false value to prevent the alpha channel from being blended into the image's colors.
4. Enable Alpha Channel Preservation: Employ imagesavealpha() with a true value to maintain the full transparency range.

By implementing these modifications, the alpha channel information in the PNG image will be preserved, preventing its conversion to a black background. The updated code would resemble the following:

<code class="php"><?php // ... Before imagecreatetruecolor()

$dimg = imagecreatetruecolor($width_new, $height_new); // png ?: gif

// start changes
switch ($stype) {

    case 'gif':
    case 'png':
        // integer representation of the color black (rgb: 0,0,0)
        $background = imagecolorallocate($dimg , 0, 0, 0);
        // removing the black from the placeholder
        imagecolortransparent($dimg, $background);

        // turning off alpha blending (to ensure alpha channel information
        // is preserved, rather than removed (blending with the rest of the
        // image in the form of black))
        imagealphablending($dimg, false);

        // turning on alpha channel information saving (to ensure the full range
        // of transparency is preserved)
        imagesavealpha($dimg, true);
        break;

    default:
        break;
}
// end changes

$wm = $w/$nw;
$hm = $h/$nh;

// ...

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