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PixelPaint: Change BucketTool flood fill algorithm

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This resolves some cases where the existing filling algorithm could get
stuck in a recursion loop and evenutally overflow the stack.
This commit is contained in:
Timothy Slater 2022-08-29 13:25:34 -05:00 committed by Andreas Kling
parent 0506f4eef8
commit 066c5acee1
Notes: sideshowbarker 2024-07-18 22:57:59 +09:00 
Author: https://github.com/tslater2006
Commit: https://github.com/SerenityOS/serenity/commit/066c5acee1
Pull-request: https://github.com/SerenityOS/serenity/pull/15074
1 changed files with 32 additions and 68 deletions
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100
Userland/Applications/PixelPaint/Tools/BucketTool.cpp
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@ -10,6 +10,7 @@
#include "BucketTool.h"
#include "../ImageEditor.h"
#include "../Layer.h"
#include "../Mask.h"
#include <AK/HashTable.h>
#include <AK/Queue.h>
#include <LibGUI/BoxLayout.h>
@ -35,76 +36,12 @@ static float color_distance_squared(Gfx::Color const& lhs, Gfx::Color const& rhs
return (a * a + b * b + c * c + d * d) / (4.0f * 255.0f * 255.0f);
}
static bool can_paint(int x, int y, Gfx::Bitmap& bitmap, Gfx::Color const& target_color, float threshold_normalized_squared)
static bool can_paint(Gfx::IntPoint point, Gfx::Bitmap& bitmap, Gfx::Color const& target_color, float threshold_normalized_squared)
{
auto pixel_color = bitmap.get_pixel<Gfx::StorageFormat::BGRA8888>(x, y);
auto pixel_color = bitmap.get_pixel<Gfx::StorageFormat::BGRA8888>(point.x(), point.y());
return color_distance_squared(pixel_color, target_color) <= threshold_normalized_squared;
}
static void fill_core(int, int, Gfx::Bitmap&, Gfx::Color const&, Gfx::Color const&, float);
static void fill_start(int x, int y, Gfx::Bitmap& bitmap, Gfx::Color const& target_color, Gfx::Color const& fill_color, float threshold_normalized_squared)
{
// Move as far up and to the left as we can first and then start filling
while (true) {
int previous_x = x;
int previous_y = y;
while (y != 0 && can_paint(x, y - 1, bitmap, target_color, threshold_normalized_squared))
y--;
while (x != 0 && can_paint(x - 1, y, bitmap, target_color, threshold_normalized_squared))
x--;
if (x == previous_x && y == previous_y)
break;
}
fill_core(x, y, bitmap, target_color, fill_color, threshold_normalized_squared);
}
static void fill_core(int x, int y, Gfx::Bitmap& bitmap, Gfx::Color const& target_color, Gfx::Color const& fill_color, float threshold_normalized_squared)
{
int prev_row_length = 0;
do {
int row_length = 0;
int start_x = x;
// To handle the case where the previous row overhangs the current row without recursion, move x to the right until we can paint.
// If we can't fill any more without extending beyond the previous row, return.
// The else branch handles the opposite case, and moves x to the left and checks above it for a spot to start filling from.
if (prev_row_length != 0 && !can_paint(x, y, bitmap, target_color, threshold_normalized_squared)) {
do {
if (--prev_row_length == 0)
return;
} while (!can_paint(++x, y, bitmap, target_color, threshold_normalized_squared));
start_x = x;
} else {
for (; x != 0 && can_paint(x - 1, y, bitmap, target_color, threshold_normalized_squared); row_length++, prev_row_length++) {
bitmap.set_pixel<Gfx::StorageFormat::BGRA8888>(--x, y, fill_color);
if (y != 0 && can_paint(x, y - 1, bitmap, target_color, threshold_normalized_squared))
fill_start(x, y - 1, bitmap, target_color, fill_color, threshold_normalized_squared);
}
}
// Fill this row to the right as much as we can
for (; start_x < bitmap.width() && can_paint(start_x, y, bitmap, target_color, threshold_normalized_squared); row_length++, start_x++) {
bitmap.set_pixel<Gfx::StorageFormat::BGRA8888>(start_x, y, fill_color);
}
// If the previous row was longer than this row, look beyond the end of this row for pixels to fill until reaching the end of the previous row.
// The else branch handles the opposite case, where the previous row was shorter. Look beyond the end of the previous row up into it for pixels to fill.
if (row_length < prev_row_length) {
for (int prev_row_end = x + prev_row_length; ++start_x < prev_row_end;) {
if (can_paint(start_x, y, bitmap, target_color, threshold_normalized_squared))
fill_core(start_x, y, bitmap, target_color, fill_color, threshold_normalized_squared);
}
} else if (row_length > prev_row_length && y != 0) {
for (int upward_x = x + prev_row_length; ++upward_x < start_x;) {
if (can_paint(upward_x, y - 1, bitmap, target_color, threshold_normalized_squared))
fill_start(upward_x, y - 1, bitmap, target_color, fill_color, threshold_normalized_squared);
}
}
prev_row_length = row_length;
} while (prev_row_length != 0 && ++y < bitmap.height());
}
static void flood_fill(Gfx::Bitmap& bitmap, Gfx::IntPoint const& start_position, Color target_color, Color fill_color, int threshold)
{
VERIFY(bitmap.bpp() == 32);
@ -117,8 +54,35 @@ static void flood_fill(Gfx::Bitmap& bitmap, Gfx::IntPoint const& start_position,
float threshold_normalized_squared = (threshold / 100.0f) * (threshold / 100.0f);
if (can_paint(start_position.x(), start_position.y(), bitmap, target_color, threshold_normalized_squared))
fill_start(start_position.x(), start_position.y(), bitmap, target_color, fill_color, threshold_normalized_squared);
// Create Mask which will track already-colored pixels
Mask flood_mask = Mask::empty(bitmap.rect());
Queue<Gfx::IntPoint> points_to_visit = Queue<Gfx::IntPoint>();
points_to_visit.enqueue({ start_position.x(), start_position.y() });
bitmap.set_pixel<Gfx::StorageFormat::BGRA8888>(start_position.x(), start_position.y(), fill_color);
flood_mask.set(start_position.x(), start_position.y(), 1);
// This implements a non-recursive flood fill. This is a breadth-first search of paintable neighbors
// As we find neighbors that are paintable we update their pixel, 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) {
if (!bitmap.rect().contains(candidate_point))
continue;
if (flood_mask.get(candidate_point.x(), candidate_point.y()) == 0 && can_paint(candidate_point, bitmap, target_color, threshold_normalized_squared)) {
points_to_visit.enqueue(candidate_point);
bitmap.set_pixel<Gfx::StorageFormat::BGRA8888>(candidate_point.x(), candidate_point.y(), fill_color);
}
flood_mask.set(candidate_point.x(), candidate_point.y(), 0xFF);
}
}
}
void BucketTool::on_mousedown(Layer* layer, MouseEvent& event)