ladybird/Userland/Libraries/LibGfx/Bitmap.cpp

/*
 * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2022, Timothy Slater <tslater2006@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Bitmap.h>
#include <AK/Checked.h>
#include <AK/DeprecatedString.h>
#include <AK/LexicalPath.h>
#include <AK/Memory.h>
#include <AK/MemoryStream.h>
#include <AK/Optional.h>
#include <AK/Queue.h>
#include <AK/ScopeGuard.h>
#include <AK/Try.h>
#include <LibCore/MappedFile.h>
#include <LibCore/System.h>
#include <LibGfx/Bitmap.h>
#include <LibGfx/ImageDecoder.h>
#include <LibGfx/ShareableBitmap.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/mman.h>

namespace Gfx {

struct BackingStore {
    void* data { nullptr };
    size_t pitch { 0 };
    size_t size_in_bytes { 0 };
};

size_t Bitmap::minimum_pitch(size_t physical_width, BitmapFormat format)
{
    size_t element_size;
    switch (determine_storage_format(format)) {
    case StorageFormat::Indexed8:
        element_size = 1;
        break;
    case StorageFormat::BGRx8888:
    case StorageFormat::BGRA8888:
    case StorageFormat::RGBA8888:
        element_size = 4;
        break;
    default:
        VERIFY_NOT_REACHED();
    }

    return physical_width * element_size;
}

static bool size_would_overflow(BitmapFormat format, IntSize size, int scale_factor)
{
    if (size.width() < 0 || size.height() < 0)
        return true;
    // This check is a bit arbitrary, but should protect us from most shenanigans:
    if (size.width() >= INT16_MAX || size.height() >= INT16_MAX || scale_factor < 1 || scale_factor > 4)
        return true;
    // In contrast, this check is absolutely necessary:
    size_t pitch = Bitmap::minimum_pitch(size.width() * scale_factor, format);
    return Checked<size_t>::multiplication_would_overflow(pitch, size.height() * scale_factor);
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_create(BitmapFormat format, IntSize size, int scale_factor)
{
    auto backing_store = TRY(Bitmap::allocate_backing_store(format, size, scale_factor));
    return AK::adopt_nonnull_ref_or_enomem(new (nothrow) Bitmap(format, size, scale_factor, backing_store));
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_create_shareable(BitmapFormat format, IntSize size, int scale_factor)
{
    if (size_would_overflow(format, size, scale_factor))
        return Error::from_string_literal("Gfx::Bitmap::try_create_shareable size overflow");

    auto const pitch = minimum_pitch(size.width() * scale_factor, format);
    auto const data_size = size_in_bytes(pitch, size.height() * scale_factor);

    auto buffer = TRY(Core::AnonymousBuffer::create_with_size(round_up_to_power_of_two(data_size, PAGE_SIZE)));
    auto bitmap = TRY(Bitmap::try_create_with_anonymous_buffer(format, buffer, size, scale_factor, {}));
    return bitmap;
}

Bitmap::Bitmap(BitmapFormat format, IntSize size, int scale_factor, BackingStore const& backing_store)
    : m_size(size)
    , m_scale(scale_factor)
    , m_data(backing_store.data)
    , m_pitch(backing_store.pitch)
    , m_format(format)
{
    VERIFY(!m_size.is_empty());
    VERIFY(!size_would_overflow(format, size, scale_factor));
    VERIFY(m_data);
    VERIFY(backing_store.size_in_bytes == size_in_bytes());
    allocate_palette_from_format(format, {});
    m_needs_munmap = true;
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_create_wrapper(BitmapFormat format, IntSize size, int scale_factor, size_t pitch, void* data)
{
    if (size_would_overflow(format, size, scale_factor))
        return Error::from_string_literal("Gfx::Bitmap::try_create_wrapper size overflow");
    return adopt_ref(*new Bitmap(format, size, scale_factor, pitch, data));
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_load_from_file(StringView path, int scale_factor)
{
    if (scale_factor > 1 && path.starts_with("/res/"sv)) {
        auto load_scaled_bitmap = [](StringView path, int scale_factor) -> ErrorOr<NonnullRefPtr<Bitmap>> {
            LexicalPath lexical_path { path };
            StringBuilder highdpi_icon_path;
            TRY(highdpi_icon_path.try_appendff("{}/{}-{}x.{}", lexical_path.dirname(), lexical_path.title(), scale_factor, lexical_path.extension()));

            auto highdpi_icon_string = highdpi_icon_path.string_view();
            auto fd = TRY(Core::System::open(highdpi_icon_string, O_RDONLY));

            auto bitmap = TRY(try_load_from_fd_and_close(fd, highdpi_icon_string));
            if (bitmap->width() % scale_factor != 0 || bitmap->height() % scale_factor != 0)
                return Error::from_string_literal("Bitmap::try_load_from_file: HighDPI image size should be divisible by scale factor");
            bitmap->m_size.set_width(bitmap->width() / scale_factor);
            bitmap->m_size.set_height(bitmap->height() / scale_factor);
            bitmap->m_scale = scale_factor;
            return bitmap;
        };

        auto scaled_bitmap_or_error = load_scaled_bitmap(path, scale_factor);
        if (!scaled_bitmap_or_error.is_error())
            return scaled_bitmap_or_error.release_value();

        auto error = scaled_bitmap_or_error.release_error();
        if (!(error.is_syscall() && error.code() == ENOENT)) {
            dbgln("Couldn't load scaled bitmap: {}", error);
            dbgln("Trying base scale instead.");
        }
    }

    auto fd = TRY(Core::System::open(path, O_RDONLY));
    return try_load_from_fd_and_close(fd, path);
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_load_from_fd_and_close(int fd, StringView path)
{
    auto file = TRY(Core::MappedFile::map_from_fd_and_close(fd, path));
    if (auto decoder = ImageDecoder::try_create(file->bytes())) {
        auto frame = TRY(decoder->frame(0));
        if (auto& bitmap = frame.image)
            return bitmap.release_nonnull();
    }

    return Error::from_string_literal("Gfx::Bitmap unable to load from fd");
}

Bitmap::Bitmap(BitmapFormat format, IntSize size, int scale_factor, size_t pitch, void* data)
    : m_size(size)
    , m_scale(scale_factor)
    , m_data(data)
    , m_pitch(pitch)
    , m_format(format)
{
    VERIFY(pitch >= minimum_pitch(size.width() * scale_factor, format));
    VERIFY(!size_would_overflow(format, size, scale_factor));
    // FIXME: assert that `data` is actually long enough!

    allocate_palette_from_format(format, {});
}

static bool check_size(IntSize size, int scale_factor, BitmapFormat format, unsigned actual_size)
{
    // FIXME: Code duplication of size_in_bytes() and m_pitch
    unsigned expected_size_min = Bitmap::minimum_pitch(size.width() * scale_factor, format) * size.height() * scale_factor;
    unsigned expected_size_max = round_up_to_power_of_two(expected_size_min, PAGE_SIZE);
    if (expected_size_min > actual_size || actual_size > expected_size_max) {
        // Getting here is most likely an error.
        dbgln("Constructing a shared bitmap for format {} and size {} @ {}x, which demands {} bytes, which rounds up to at most {}.",
            static_cast<int>(format),
            size,
            scale_factor,
            expected_size_min,
            expected_size_max);

        dbgln("However, we were given {} bytes, which is outside this range?! Refusing cowardly.", actual_size);
        return false;
    }
    return true;
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_create_with_anonymous_buffer(BitmapFormat format, Core::AnonymousBuffer buffer, IntSize size, int scale_factor, Vector<ARGB32> const& palette)
{
    if (size_would_overflow(format, size, scale_factor))
        return Error::from_string_literal("Gfx::Bitmap::try_create_with_anonymous_buffer size overflow");

    return adopt_nonnull_ref_or_enomem(new (nothrow) Bitmap(format, move(buffer), size, scale_factor, palette));
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_create_from_serialized_byte_buffer(ByteBuffer&& buffer)
{
    return try_create_from_serialized_bytes(buffer.bytes());
}

/// Read a bitmap as described by:
/// - actual size
/// - width
/// - height
/// - scale_factor
/// - format
/// - palette count
/// - palette data (= palette count * BGRA8888)
/// - image data (= actual size * u8)
ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::try_create_from_serialized_bytes(ReadonlyBytes bytes)
{
    InputMemoryStream stream { bytes };
    size_t actual_size;
    unsigned width;
    unsigned height;
    unsigned scale_factor;
    BitmapFormat format;
    unsigned palette_size;
    Vector<ARGB32> palette;

    auto read = [&]<typename T>(T& value) {
        if (stream.read({ &value, sizeof(T) }) != sizeof(T))
            return false;
        return true;
    };

    if (!read(actual_size) || !read(width) || !read(height) || !read(scale_factor) || !read(format) || !read(palette_size))
        return Error::from_string_literal("Gfx::Bitmap::try_create_from_serialized_byte_buffer: decode failed");

    if (format > BitmapFormat::BGRA8888 || format < BitmapFormat::Indexed1)
        return Error::from_string_literal("Gfx::Bitmap::try_create_from_serialized_byte_buffer: decode failed");

    if (!check_size({ width, height }, scale_factor, format, actual_size))
        return Error::from_string_literal("Gfx::Bitmap::try_create_from_serialized_byte_buffer: decode failed");

    palette.ensure_capacity(palette_size);
    for (size_t i = 0; i < palette_size; ++i) {
        if (!read(palette[i]))
            return Error::from_string_literal("Gfx::Bitmap::try_create_from_serialized_byte_buffer: decode failed");
    }

    if (stream.remaining() < actual_size)
        return Error::from_string_literal("Gfx::Bitmap::try_create_from_serialized_byte_buffer: decode failed");

    auto data = stream.bytes().slice(stream.offset(), actual_size);

    auto bitmap = TRY(Bitmap::try_create(format, { width, height }, scale_factor));

    bitmap->m_palette = new ARGB32[palette_size];
    memcpy(bitmap->m_palette, palette.data(), palette_size * sizeof(ARGB32));

    data.copy_to({ bitmap->scanline(0), bitmap->size_in_bytes() });
    return bitmap;
}

ByteBuffer Bitmap::serialize_to_byte_buffer() const
{
    // FIXME: Somehow handle possible OOM situation here.
    auto buffer = ByteBuffer::create_uninitialized(sizeof(size_t) + 4 * sizeof(unsigned) + sizeof(BitmapFormat) + sizeof(ARGB32) * palette_size(m_format) + size_in_bytes()).release_value_but_fixme_should_propagate_errors();
    OutputMemoryStream stream { buffer };

    auto write = [&]<typename T>(T value) {
        if (stream.write({ &value, sizeof(T) }) != sizeof(T))
            return false;
        return true;
    };

    auto palette = palette_to_vector();

    if (!write(size_in_bytes()) || !write((unsigned)size().width()) || !write((unsigned)size().height()) || !write((unsigned)scale()) || !write(m_format) || !write((unsigned)palette.size()))
        return {};

    for (auto& p : palette) {
        if (!write(p))
            return {};
    }

    auto size = size_in_bytes();
    VERIFY(stream.remaining() == size);
    if (stream.write({ scanline(0), size }) != size)
        return {};

    return buffer;
}

Bitmap::Bitmap(BitmapFormat format, Core::AnonymousBuffer buffer, IntSize size, int scale_factor, Vector<ARGB32> const& palette)
    : m_size(size)
    , m_scale(scale_factor)
    , m_data(buffer.data<void>())
    , m_pitch(minimum_pitch(size.width() * scale_factor, format))
    , m_format(format)
    , m_buffer(move(buffer))
{
    VERIFY(!is_indexed() || !palette.is_empty());
    VERIFY(!size_would_overflow(format, size, scale_factor));

    if (is_indexed(m_format))
        allocate_palette_from_format(m_format, palette);
}

ErrorOr<NonnullRefPtr<Gfx::Bitmap>> Bitmap::clone() const
{
    auto new_bitmap = TRY(Bitmap::try_create(format(), size(), scale()));

    VERIFY(size_in_bytes() == new_bitmap->size_in_bytes());
    memcpy(new_bitmap->scanline(0), scanline(0), size_in_bytes());

    return new_bitmap;
}

ErrorOr<NonnullRefPtr<Gfx::Bitmap>> Bitmap::rotated(Gfx::RotationDirection rotation_direction) const
{
    auto new_bitmap = TRY(Gfx::Bitmap::try_create(this->format(), { height(), width() }, scale()));

    auto w = this->physical_width();
    auto h = this->physical_height();
    for (int i = 0; i < w; i++) {
        for (int j = 0; j < h; j++) {
            Color color;
            if (rotation_direction == Gfx::RotationDirection::CounterClockwise)
                color = this->get_pixel(w - i - 1, j);
            else
                color = this->get_pixel(i, h - j - 1);

            new_bitmap->set_pixel(j, i, color);
        }
    }

    return new_bitmap;
}

ErrorOr<NonnullRefPtr<Gfx::Bitmap>> Bitmap::flipped(Gfx::Orientation orientation) const
{
    auto new_bitmap = TRY(Gfx::Bitmap::try_create(this->format(), { width(), height() }, scale()));

    auto w = this->physical_width();
    auto h = this->physical_height();
    for (int i = 0; i < w; i++) {
        for (int j = 0; j < h; j++) {
            Color color = this->get_pixel(i, j);
            if (orientation == Orientation::Vertical)
                new_bitmap->set_pixel(i, h - j - 1, color);
            else
                new_bitmap->set_pixel(w - i - 1, j, color);
        }
    }

    return new_bitmap;
}

ErrorOr<NonnullRefPtr<Gfx::Bitmap>> Bitmap::scaled(int sx, int sy) const
{
    VERIFY(sx >= 0 && sy >= 0);
    if (sx == 1 && sy == 1)
        return NonnullRefPtr { *this };

    auto new_bitmap = TRY(Gfx::Bitmap::try_create(format(), { width() * sx, height() * sy }, scale()));

    auto old_width = physical_width();
    auto old_height = physical_height();

    for (int y = 0; y < old_height; y++) {
        for (int x = 0; x < old_width; x++) {
            auto color = get_pixel(x, y);

            auto base_x = x * sx;
            auto base_y = y * sy;
            for (int new_y = base_y; new_y < base_y + sy; new_y++) {
                for (int new_x = base_x; new_x < base_x + sx; new_x++) {
                    new_bitmap->set_pixel(new_x, new_y, color);
                }
            }
        }
    }

    return new_bitmap;
}

// http://fourier.eng.hmc.edu/e161/lectures/resize/node3.html
ErrorOr<NonnullRefPtr<Gfx::Bitmap>> Bitmap::scaled(float sx, float sy) const
{
    VERIFY(sx >= 0.0f && sy >= 0.0f);
    if (floorf(sx) == sx && floorf(sy) == sy)
        return scaled(static_cast<int>(sx), static_cast<int>(sy));

    int scaled_width = (int)ceilf(sx * (float)width());
    int scaled_height = (int)ceilf(sy * (float)height());

    auto new_bitmap = TRY(Gfx::Bitmap::try_create(format(), { scaled_width, scaled_height }, scale()));

    auto old_width = physical_width();
    auto old_height = physical_height();
    auto new_width = new_bitmap->physical_width();
    auto new_height = new_bitmap->physical_height();

    // The interpolation goes out of bounds on the bottom- and right-most edges.
    // We handle those in two specialized loops not only to make them faster, but
    // also to avoid four branch checks for every pixel.

    for (int y = 0; y < new_height - 1; y++) {
        for (int x = 0; x < new_width - 1; x++) {
            auto p = static_cast<float>(x) * static_cast<float>(old_width - 1) / static_cast<float>(new_width - 1);
            auto q = static_cast<float>(y) * static_cast<float>(old_height - 1) / static_cast<float>(new_height - 1);

            int i = floorf(p);
            int j = floorf(q);
            float u = p - static_cast<float>(i);
            float v = q - static_cast<float>(j);

            auto a = get_pixel(i, j);
            auto b = get_pixel(i + 1, j);
            auto c = get_pixel(i, j + 1);
            auto d = get_pixel(i + 1, j + 1);

            auto e = a.interpolate(b, u);
            auto f = c.interpolate(d, u);
            auto color = e.interpolate(f, v);
            new_bitmap->set_pixel(x, y, color);
        }
    }

    // Bottom strip (excluding last pixel)
    auto old_bottom_y = old_height - 1;
    auto new_bottom_y = new_height - 1;
    for (int x = 0; x < new_width - 1; x++) {
        auto p = static_cast<float>(x) * static_cast<float>(old_width - 1) / static_cast<float>(new_width - 1);

        int i = floorf(p);
        float u = p - static_cast<float>(i);

        auto a = get_pixel(i, old_bottom_y);
        auto b = get_pixel(i + 1, old_bottom_y);
        auto color = a.interpolate(b, u);
        new_bitmap->set_pixel(x, new_bottom_y, color);
    }

    // Right strip (excluding last pixel)
    auto old_right_x = old_width - 1;
    auto new_right_x = new_width - 1;
    for (int y = 0; y < new_height - 1; y++) {
        auto q = static_cast<float>(y) * static_cast<float>(old_height - 1) / static_cast<float>(new_height - 1);

        int j = floorf(q);
        float v = q - static_cast<float>(j);

        auto c = get_pixel(old_right_x, j);
        auto d = get_pixel(old_right_x, j + 1);

        auto color = c.interpolate(d, v);
        new_bitmap->set_pixel(new_right_x, y, color);
    }

    // Bottom-right pixel
    new_bitmap->set_pixel(new_width - 1, new_height - 1, get_pixel(physical_width() - 1, physical_height() - 1));

    return new_bitmap;
}

ErrorOr<NonnullRefPtr<Gfx::Bitmap>> Bitmap::cropped(Gfx::IntRect crop, Optional<BitmapFormat> new_bitmap_format) const
{
    auto new_bitmap = TRY(Gfx::Bitmap::try_create(new_bitmap_format.value_or(format()), { crop.width(), crop.height() }, 1));

    for (int y = 0; y < crop.height(); ++y) {
        for (int x = 0; x < crop.width(); ++x) {
            int global_x = x + crop.left();
            int global_y = y + crop.top();
            if (global_x >= physical_width() || global_y >= physical_height() || global_x < 0 || global_y < 0) {
                new_bitmap->set_pixel(x, y, Gfx::Color::Black);
            } else {
                new_bitmap->set_pixel(x, y, get_pixel(global_x, global_y));
            }
        }
    }
    return new_bitmap;
}

ErrorOr<NonnullRefPtr<Bitmap>> Bitmap::to_bitmap_backed_by_anonymous_buffer() const
{
    if (m_buffer.is_valid())
        return NonnullRefPtr { *this };
    auto buffer = TRY(Core::AnonymousBuffer::create_with_size(round_up_to_power_of_two(size_in_bytes(), PAGE_SIZE)));
    auto bitmap = TRY(Bitmap::try_create_with_anonymous_buffer(m_format, move(buffer), size(), scale(), palette_to_vector()));
    memcpy(bitmap->scanline(0), scanline(0), size_in_bytes());
    return bitmap;
}

void Bitmap::invert()
{
    for (auto y = 0; y < height(); y++) {
        for (auto x = 0; x < width(); x++)
            set_pixel(x, y, get_pixel(x, y).inverted());
    }
}

Bitmap::~Bitmap()
{
    if (m_needs_munmap) {
        int rc = munmap(m_data, size_in_bytes());
        VERIFY(rc == 0);
    }
    m_data = nullptr;
    delete[] m_palette;
}

void Bitmap::set_mmap_name([[maybe_unused]] DeprecatedString const& name)
{
    VERIFY(m_needs_munmap);
#ifdef AK_OS_SERENITY
    ::set_mmap_name(m_data, size_in_bytes(), name.characters());
#endif
}

void Bitmap::fill(Color color)
{
    VERIFY(!is_indexed(m_format));
    for (int y = 0; y < physical_height(); ++y) {
        auto* scanline = this->scanline(y);
        fast_u32_fill(scanline, color.value(), physical_width());
    }
}

void Bitmap::set_volatile()
{
    if (m_volatile)
        return;
#ifdef AK_OS_SERENITY
    int rc = madvise(m_data, size_in_bytes(), MADV_SET_VOLATILE);
    if (rc < 0) {
        perror("madvise(MADV_SET_VOLATILE)");
        VERIFY_NOT_REACHED();
    }
#endif
    m_volatile = true;
}

[[nodiscard]] bool Bitmap::set_nonvolatile(bool& was_purged)
{
    if (!m_volatile) {
        was_purged = false;
        return true;
    }

#ifdef AK_OS_SERENITY
    int rc = madvise(m_data, size_in_bytes(), MADV_SET_NONVOLATILE);
    if (rc < 0) {
        if (errno == ENOMEM) {
            was_purged = true;
            return false;
        }
        perror("madvise(MADV_SET_NONVOLATILE)");
        VERIFY_NOT_REACHED();
    }
    was_purged = rc != 0;
#endif
    m_volatile = false;
    return true;
}

Gfx::ShareableBitmap Bitmap::to_shareable_bitmap() const
{
    auto bitmap_or_error = to_bitmap_backed_by_anonymous_buffer();
    if (bitmap_or_error.is_error())
        return {};
    return Gfx::ShareableBitmap { bitmap_or_error.release_value_but_fixme_should_propagate_errors(), Gfx::ShareableBitmap::ConstructWithKnownGoodBitmap };
}

ErrorOr<BackingStore> Bitmap::allocate_backing_store(BitmapFormat format, IntSize size, int scale_factor)
{
    if (size_would_overflow(format, size, scale_factor))
        return Error::from_string_literal("Gfx::Bitmap backing store size overflow");

    auto const pitch = minimum_pitch(size.width() * scale_factor, format);
    auto const data_size_in_bytes = size_in_bytes(pitch, size.height() * scale_factor);

    int map_flags = MAP_ANONYMOUS | MAP_PRIVATE;
#ifdef AK_OS_SERENITY
    map_flags |= MAP_PURGEABLE;
    void* data = mmap_with_name(nullptr, data_size_in_bytes, PROT_READ | PROT_WRITE, map_flags, 0, 0, DeprecatedString::formatted("GraphicsBitmap [{}]", size).characters());
#else
    void* data = mmap(nullptr, data_size_in_bytes, PROT_READ | PROT_WRITE, map_flags, -1, 0);
#endif
    if (data == MAP_FAILED)
        return Error::from_errno(errno);
    return BackingStore { data, pitch, data_size_in_bytes };
}

void Bitmap::allocate_palette_from_format(BitmapFormat format, Vector<ARGB32> const& source_palette)
{
    size_t size = palette_size(format);
    if (size == 0)
        return;
    m_palette = new ARGB32[size];
    if (!source_palette.is_empty()) {
        VERIFY(source_palette.size() == size);
        memcpy(m_palette, source_palette.data(), size * sizeof(ARGB32));
    }
}

Vector<ARGB32> Bitmap::palette_to_vector() const
{
    Vector<ARGB32> vector;
    auto size = palette_size(m_format);
    vector.ensure_capacity(size);
    for (size_t i = 0; i < size; ++i)
        vector.unchecked_append(palette_color(i).value());
    return vector;
}

bool Bitmap::visually_equals(Bitmap const& other) const
{
    auto own_width = width();
    auto own_height = height();
    if (other.width() != own_width || other.height() != own_height)
        return false;

    for (auto y = 0; y < own_height; ++y) {
        for (auto x = 0; x < own_width; ++x) {
            if (get_pixel(x, y) != other.get_pixel(x, y))
                return false;
        }
    }

    return true;
}

Optional<Color> Bitmap::solid_color(u8 alpha_threshold) const
{
    Optional<Color> color;
    for (auto y = 0; y < height(); ++y) {
        for (auto x = 0; x < width(); ++x) {
            auto const& pixel = get_pixel(x, y);
            if (has_alpha_channel() && pixel.alpha() <= alpha_threshold)
                continue;
            if (!color.has_value())
                color = pixel;
            else if (pixel != color)
                return {};
        }
    }
    return color;
}

void Bitmap::flood_visit_from_point(Gfx::IntPoint start_point, int threshold,
    Function<void(Gfx::IntPoint location)> pixel_reached)
{

    VERIFY(rect().contains(start_point));

    auto target_color = get_pixel(start_point.x(), start_point.y());

    float threshold_normalized_squared = (threshold / 100.0f) * (threshold / 100.0f);

    Queue<Gfx::IntPoint> points_to_visit = Queue<Gfx::IntPoint>();

    points_to_visit.enqueue(start_point);
    pixel_reached(start_point);
    auto flood_mask = AK::Bitmap::must_create(width() * height(), false);

    flood_mask.set(width() * start_point.y() + start_point.x(), true);

    // This implements a non-recursive flood fill. This is a breadth-first search of paintable neighbors
    // As we find neighbors that are reachable we call the location_reached callback, add them to the queue, and mark them in the mask
    while (!points_to_visit.is_empty()) {
        auto current_point = points_to_visit.dequeue();
        auto candidate_points = Array {
            current_point.moved_left(1),
            current_point.moved_right(1),
            current_point.moved_up(1),
            current_point.moved_down(1)
        };
        for (auto candidate_point : candidate_points) {
            auto flood_mask_index = width() * candidate_point.y() + candidate_point.x();
            if (!rect().contains(candidate_point))
                continue;

            auto pixel_color = get_pixel<Gfx::StorageFormat::BGRA8888>(candidate_point.x(), candidate_point.y());
            auto can_paint = pixel_color.distance_squared_to(target_color) <= threshold_normalized_squared;

            if (flood_mask.get(flood_mask_index) == false && can_paint) {
                points_to_visit.enqueue(candidate_point);
                pixel_reached(candidate_point);
            }

            flood_mask.set(flood_mask_index, true);
        }
    }
}

}