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Code Issues Projects Releases Packages Wiki Activity Actions 6

Painter: Support diagonal lines with dy>dx, and apply clipping as well.

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This commit is contained in:
Andreas Kling 2019-05-07 17:01:55 +02:00
parent 4f77b4e5bc
commit e8d395b14d
Notes: sideshowbarker 2024-07-19 14:12:26 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/e8d395b14df
1 changed files with 48 additions and 23 deletions
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71
SharedGraphics/Painter.cpp
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@ -478,6 +478,8 @@ void Painter::set_pixel(const Point& p, Color color)
void Painter::draw_line(const Point& p1, const Point& p2, Color color)
{
auto clip_rect = this->clip_rect();
auto point1 = p1;
point1.move_by(state().translation);
@ -487,37 +489,34 @@ void Painter::draw_line(const Point& p1, const Point& p2, Color color)
// Special case: vertical line.
if (point1.x() == point2.x()) {
const int x = point1.x();
if (x < clip_rect().left() || x > clip_rect().right())
if (x < clip_rect.left() || x > clip_rect.right())
return;
if (point1.y() > point2.y())
swap(point1, point2);
if (point1.y() > clip_rect().bottom())
if (point1.y() > clip_rect.bottom())
return;
if (point2.y() < clip_rect().top())
if (point2.y() < clip_rect.top())
return;
int min_y = max(point1.y(), clip_rect().top());
int max_y = min(point2.y(), clip_rect().bottom());
int min_y = max(point1.y(), clip_rect.top());
int max_y = min(point2.y(), clip_rect.bottom());
for (int y = min_y; y <= max_y; ++y)
set_pixel_with_draw_op(m_target->scanline(y)[x], color);
return;
}
if (point1.x() > point2.x())
swap(point1, point2);
// Special case: horizontal line.
if (point1.y() == point2.y()) {
const int y = point1.y();
if (y < clip_rect().top() || y > clip_rect().bottom())
if (y < clip_rect.top() || y > clip_rect.bottom())
return;
if (point1.x() > point2.x())
swap(point1, point2);
if (point1.x() > clip_rect().right())
if (point1.x() > clip_rect.right())
return;
if (point2.x() < clip_rect().left())
if (point2.x() < clip_rect.left())
return;
int min_x = max(point1.x(), clip_rect().left());
int max_x = min(point2.x(), clip_rect().right());
int min_x = max(point1.x(), clip_rect.left());
int max_x = min(point2.x(), clip_rect.right());
auto* pixels = m_target->scanline(point1.y());
if (draw_op() == DrawOp::Copy) {
fast_dword_fill(pixels + min_x, color.value(), max_x - min_x + 1);
@ -528,21 +527,47 @@ void Painter::draw_line(const Point& p1, const Point& p2, Color color)
return;
}
// FIXME: Implement clipping below.
const double adx = abs(point2.x() - point1.x());
const double ady = abs(point2.y() - point1.y());
if (adx > ady) {
if (point1.x() > point2.x())
swap(point1, point2);
} else {
if (point1.y() > point2.y())
swap(point1, point2);
}
// FIXME: Implement clipping below.
const double dx = point2.x() - point1.x();
const double dy = point2.y() - point1.y();
const double delta_error = fabs(dy / dx);
double error = 0;
const double y_step = dy == 0 ? 0 : (dy > 0 ? 1 : -1);
int y = point1.y();
for (int x = point1.x(); x <= point2.x(); ++x) {
m_target->scanline(y)[x] = color.value();
error += delta_error;
if (error >= 0.5) {
y = (double)y + y_step;
error -= 1.0;
if (dx > dy) {
const double y_step = dy == 0 ? 0 : (dy > 0 ? 1 : -1);
const double delta_error = fabs(dy / dx);
int y = point1.y();
for (int x = point1.x(); x <= point2.x(); ++x) {
if (clip_rect.contains(x, y))
m_target->scanline(y)[x] = color.value();
error += delta_error;
if (error >= 0.5) {
y = (double)y + y_step;
error -= 1.0;
}
}
} else {
const double x_step = dx == 0 ? 0 : (dx > 0 ? 1 : -1);
const double delta_error = fabs(dx / dy);
int x = point1.x();
for (int y = point1.y(); y <= point2.y(); ++y) {
if (clip_rect.contains(x, y))
m_target->scanline(y)[x] = color.value();
error += delta_error;
if (error >= 0.5) {
x = (double)x + x_step;
error -= 1.0;
}
}
}
}