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PixelPaint: Allow copying arbitrary selections

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This replaces the naive copy algorithm that only supported rectangular
and 100% opaque selections with a more general approach that supports
any shape and alpha value.

Note that we now make a brand new bitmap with a hardcoded format instead
of just cropping the layer's existing bitmap. This is done to ensure
that the final clipboard image will have an alpha channel.
This commit is contained in:
Davipb 2021-06-20 10:59:21 -03:00 • committed by Andreas Kling
parent e58f78e667
commit 20b2c46019
1 changed files with 30 additions and 3 deletions
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33
Userland/Applications/PixelPaint/Layer.cpp
View file

@ -92,9 +92,36 @@ void Layer::set_name(String name)
RefPtr<Gfx::Bitmap> Layer::try_copy_bitmap(Selection const& selection) const
{
auto bounding_rect = selection.bounding_rect().translated(-m_location);
// FIXME: This needs to be smarter once we add more complex selections.
return m_bitmap->cropped(bounding_rect);
auto selection_rect = selection.bounding_rect();
auto result = Gfx::Bitmap::create(Gfx::BitmapFormat::BGRA8888, selection_rect.size());
VERIFY(result->has_alpha_channel());
for (int y = selection_rect.top(); y <= selection_rect.bottom(); y++) {
for (int x = selection_rect.left(); x <= selection_rect.right(); x++) {
Gfx::IntPoint image_point { x, y };
auto layer_point = image_point - m_location;
auto result_point = image_point - selection_rect.top_left();
if (!m_bitmap->physical_rect().contains(layer_point)) {
result->set_pixel(result_point, Gfx::Color::Transparent);
continue;
}
auto pixel = m_bitmap->get_pixel(layer_point);
// Widen to int before multiplying to avoid overflow issues
auto pixel_alpha = static_cast<int>(pixel.alpha());
auto selection_alpha = static_cast<int>(selection.get_selection_alpha(image_point));
auto new_alpha = (pixel_alpha * selection_alpha) / 0xFF;
pixel.set_alpha(static_cast<u8>(clamp(new_alpha, 0, 0xFF)));
result->set_pixel(result_point, pixel);
}
}
return result;
}
}