imagecolorallocatealpha

Description
Syntax
Examples
Links

Description

The imagecolorallocatealpha of Image for PHP allocate a color for an image.

Syntax

imagecolorallocatealpha(
    GdImage $image,
    int $red,
    int $green,
    int $blue,
    int $alpha
): int|false

Parameters

image

A GdImage object, returned by one of the image creation functions, such as imagecreatetruecolor().

red

Value of red component.

green

Value of green component.

blue

Value of blue component.

alpha

A value between 0 and 127. 0 is completely opaque and 127 is completely transparent.

Return

A color identifier or false if the allocation failed.

Warning: This function may return Boolean false, but may also return a non-Boolean value which evaluates to false. Use the === operator for testing the return value of this function.

Examples

1 · red green blue · decimal

<?

$width = 100;
$height = 100;
$image = imagecreate($width, $height);

$red = 255;
$green = 255;
$blue = 255;
$alpha = 64;

$return = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

echo $return;

2 · red green blue · hexadecimal

<?

$width = 100;
$height = 100;
$image = imagecreate($width, $height);

$red = 0xff;
$green = 0xff;
$blue = 0xff;
$alpha = 64;

$return = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

echo $return;

3 · return

<?

$width = 100;
$height = 100;
$image = imagecreate($width, $height);

$red = 255;
$green = 255;
$blue = 255;
$alpha = 64;
$background = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$red = 255;
$green = 0;
$blue = 0;
$alpha = 64;
$r = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$red = 0;
$green = 255;
$blue = 0;
$alpha = 64;
$g = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$red = 0;
$green = 0;
$blue = 255;
$alpha = 64;
$b = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

echo $background . $r . $g . $b;

4 · base64

<?

$width = 100;
$height = 100;
$image = imagecreatetruecolor($width, $height);

$enable = true;
imagesavealpha($image, $enable);

$red = 255;
$green = 255;
$blue = 255;
$alpha = 64;
$background = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$x = 0;
$y = 0;
imagefill($image, $x, $y, $background);

$red = 255;
$green = 0;
$blue = 0;
$alpha = 64;
$r = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$x1 = 0;
$y1 = 0;
$x2 = 50;
$y2 = 50;
imagefilledrectangle($image, $x1, $y1, $x2, $y2, $r);

$red = 0;
$green = 255;
$blue = 0;
$alpha = 64;
$g = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$x1 = 25;
$y1 = 25;
$x2 = 75;
$y2 = 75;
imagefilledrectangle($image, $x1, $y1, $x2, $y2, $g);

$red = 0;
$green = 0;
$blue = 255;
$alpha = 64;
$b = imagecolorallocatealpha($image, $red, $green, $blue, $alpha);

$x1 = 50;
$y1 = 50;
$x2 = 100;
$y2 = 100;
imagefilledrectangle($image, $x1, $y1, $x2, $y2, $b);

ob_start();

    imagepng($image);

$output = ob_get_clean();

echo '<!doctype html>
<html>
<body>
    <img src="data:image/png;base64,' . base64_encode($output) . '">
</body>
</html>';

<!doctype html>
<html>
<body>
    <img src="data:image/png;base64,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">
</body>
</html>