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LibTTF: Fix glyph rasterizer coverage calculation

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Stephan Unverwerth 2021-02-27 22:52:49 +01:00 • committed by Andreas Kling
parent 1fb1279cfd
commit b807d51598
1 changed files with 7 additions and 5 deletions
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12
Userland/Libraries/LibTTF/Glyf.cpp
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@ -320,17 +320,19 @@ void Rasterizer::draw_line(Gfx::FloatPoint p0, Gfx::FloatPoint p1)
m_data[line_offset + x0i + 1] += directed_dy * area; m_data[line_offset + x0i + 1] += directed_dy * area;
} else { } else {
float dydx = 1.0 / dxdy; float dydx = 1.0 / dxdy;
if (dydx < 0)
dydx = -dydx;
float x0_right = 1.0 - (x0 - x0_floor); float x0_right = 1.0 - (x0 - x0_floor);
u32 x1_floor_i = floor(x1); u32 x1_floor_i = floor(x1);
float area_upto_here = 0.5 * x0_right * x0_right * dydx; float area_upto_here = 0.5 * x0_right * x0_right * dydx;
m_data[line_offset + x0i] += direction * area_upto_here; m_data[line_offset + x0i] += direction * area_upto_here;
for (u32 x = x0i + 1; x < x1_floor_i; x++) { for (u32 x = x0i + 1; x < x1_floor_i; x++) {
x0_right += 1.0; m_data[line_offset + x] += direction * dydx;
float total_area_here = 0.5 * x0_right * x0_right * dydx; area_upto_here += dydx;
m_data[line_offset + x] += direction * (total_area_here - area_upto_here);
area_upto_here = total_area_here;
} }
m_data[line_offset + x1_floor_i] += direction * (dy - area_upto_here); float remaining_area = (dy - area_upto_here);
m_data[line_offset + x1_floor_i] += direction * remaining_area;
} }
x_cur = x_next; x_cur = x_next;