test: fix failing GD resizeCanvas for pngs with transparent bg;

tests/Manipulations/ResizeTest.php

@@ -16,17 +16,22 @@
     assertMatchesImageSnapshot($targetFile);
 })->with('drivers');
 
-it('can resize canvas of transparent pngs without loosing transparency when GD is used', function () {
-    $image = Image::useImageDriver(ImageDriver::Gd)->loadFile(getTestFile('transparent.png')); // 1640x923
+it('can resize canvas of transparent PNGs without loosing transparency when GD is used', function (ImageDriver $driver) {
+    if ($driver->driverName() !== 'gd') {
+        return $this->expectNotToPerformAssertions();
+    }
+
     $targetFile = $this->tempDir->path("{$driver->driverName()}/resize-with-transparent-png.png");
-    $transparent = imagecolorallocatealpha($canvas->image, 255, 255, 255, 127);
+    $image = $driver->loadFile(getTestFile('transparent.png')); // 1640x923
+    $transparentColor = imagecolorallocatealpha($image->image(), 255, 255, 255, 127);
+
     expect($image->getHeight())->toEqual(923);
-    expect($image->pickColor(0, 0, \Spatie\Image\Enums\ColorFormat::Int))->toEqual($transparent);
+    expect($image->pickColor(0, 0, \Spatie\Image\Enums\ColorFormat::Int))->toEqual($transparentColor);
 
     // make it square, so height is added top and bottom, bg transparent
     $image->resizeCanvas(1640, 1640, \Spatie\Image\Enums\AlignPosition::Center, false, $image->pickColor(0, 0, \Spatie\Image\Enums\ColorFormat::Rgba))->save($targetFile);
 
     $targetImage = $driver->loadFile($targetFile);
     expect($targetImage->getHeight())->toEqual(1640);
-    expect($targetImage->pickColor(0, 0, \Spatie\Image\Enums\ColorFormat::Int))->toEqual($transparent);
-});
+    expect($targetImage->pickColor(0, 0, \Spatie\Image\Enums\ColorFormat::Int))->toEqual($transparentColor);
+})->with('drivers');