Bug: `Watermark::getAlpha()` returns 0-100 range but Intervention Image v4 expects 0-1

[deluxetom]

Description

Watermark::getAlpha() returns an int in the 0-100 range (defaulting to 100), but Intervention Image v4's InsertModifier expects a float in the 0-1 range. This causes an InvalidArgumentException on every request that applies a watermark.

Versions

• league/glide: 4.0.0-beta1
• intervention/image: 4.0.0

Error

Intervention\Image\Exceptions\InvalidArgumentException: Transparency must be in range 0 to 1
  at vendor/intervention/image/src/Modifiers/InsertModifier.php:26

Root Cause

In src/Manipulators/Watermark.php:265-278:

public function getAlpha(): int
{
    $markalpha = $this->getParam('markalpha');

    if (!is_numeric($markalpha)) {
        return 100;
    }

    if ($markalpha < 0 || $markalpha > 100) {
        return 100;
    }

    return (int) $markalpha;
}

This value is passed directly to Image::insert() on line 117:

return $image->insert($watermark, intval($markx), intval($marky), $markpos, $markalpha);

However, Intervention Image v4's InsertModifier::__construct() validates that transparency is between 0 and 1:

public function __construct(
    public mixed $image,
    public int $x = 0,
    public int $y = 0,
    public string|Alignment $alignment = Alignment::TOP_LEFT,
    public float $transparency = 1
) {
    if ($this->transparency < 0 || $this->transparency > 1) {
        throw new InvalidArgumentException('Transparency must be in range 0 to 1');
    }
}

Suggested Fix

Normalize the 0-100 integer to a 0-1 float in getAlpha():

public function getAlpha(): float
{
    $markalpha = $this->getParam('markalpha');

    if (!is_numeric($markalpha)) {
        return 1.0;
    }

    if ($markalpha < 0 || $markalpha > 100) {
        return 1.0;
    }

    return (float) $markalpha / 100;
}

Steps to Reproduce

1. Configure a Glide server with a watermark filesystem
2. Set a default mark parameter (no markalpha override needed — the default 100 triggers it)
3. Request any image — the watermark manipulator throws on every request