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RenderingHelpers: Fix transformed linear gradients

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Previously, the software renderer could render transformed gradients
incorrectly. This could be seen in the backgrounds of the tabs in the
ComponentTransformsDemo when the view was rotated through around 45
degrees.

The new behaviour appears more consistent with the other renderers.
This commit is contained in:
reuk 2024-04-10 14:01:55 +01:00
parent b1861dc25c
commit 7e87d3e7a6
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1 changed files with 11 additions and 3 deletions
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14
modules/juce_graphics/native/juce_RenderingHelpers.h
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@ -318,6 +318,14 @@ struct FloatRectangleRasterisingInfo
int topAlpha, leftAlpha, bottomAlpha, rightAlpha; // alpha of each anti-aliased edge
};
// Line::findNearestPointTo will always return a point between the line's start and end, whereas
// this version assumes that the line is infinite.
static Point<float> closestPointOnInfiniteLine (const Line<float>& line, const Point<float>& point)
{
const Line perpendicularThroughPoint { point, point + line.getPointAlongLine (0.0f, 1.0f) - line.getStart() };
return line.getIntersection (perpendicularThroughPoint);
}
//==============================================================================
/** Contains classes for calculating the colour of pixels within various types of gradient. */
namespace GradientPixelIterators
@ -342,7 +350,7 @@ namespace GradientPixelIterators
p2.applyTransform (transform);
p3.applyTransform (transform);
p2 = Line<float> (p2, p3).findNearestPointTo (p1);
p2 = closestPointOnInfiniteLine ({ p2, p3 }, p1);
}
vertical = std::abs (p1.x - p2.x) < 0.001f;
@ -360,8 +368,8 @@ namespace GradientPixelIterators
}
else
{
grad = (p2.getY() - p1.y) / (double) (p1.x - p2.x);
yTerm = p1.getY() - p1.x / grad;
grad = (p2.y - p1.y) / (double) (p1.x - p2.x);
yTerm = p1.y - (p1.x / grad);
scale = roundToInt ((double) ((int64_t) numEntries << (int) numScaleBits) / (yTerm * grad - (p2.y * grad - p2.x)));
grad *= scale;
}