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Change MapProjector.ToMap() to avoid unnecessary memory alloc. #1272

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Change MapProjector.ToMap() to avoid unnecessary memory alloc. #1272

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14 changes: 7 additions & 7 deletions src/LiveChartsCore/Geo/ControlCoordinatesProjector.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,18 +60,18 @@ public ControlCoordinatesProjector(float mapWidth, float mapHeight, float offset
/// </value>
public static float[] PreferredRatio => new[] { 2f, 1f };

/// <inheritdoc cref="MapProjector.ToMap(double[])"/>
/// <inheritdoc cref="MapProjector.ToMap(LvcPointD)"/>
public override float[] ToMap(double[] point)
{
// simplified formula
return new[]
return new LvcPoint
{
// x' =
(float)(_ox + (point[0] + 180) / 360d * _w),
// x' =
X = (float)(_ox + (point.X + 180) / 360d * _w),

// y' =
(float)(_oy + (90 - point[1]) / 180d * _h)
};
// y' =
Y = (float)(_oy + (90 - point.Y) / 180d * _h)
};

// the following code explains the formula better:

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2 changes: 1 addition & 1 deletion src/LiveChartsCore/Geo/MapProjector.cs
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Expand Up @@ -52,5 +52,5 @@ public abstract class MapProjector
/// </summary>
/// <param name="point">The point.</param>
/// <returns></returns>
public abstract float[] ToMap(double[] point);
public abstract LvcPoint ToMap(LvcPointD point);
}
14 changes: 7 additions & 7 deletions src/LiveChartsCore/Geo/MercatorProjector.cs
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Expand Up @@ -62,23 +62,23 @@ public MercatorProjector(float mapWidth, float mapHeight, float offsetX, float o
/// </value>
public static float[] PreferredRatio => new[] { 1f, 1f };

/// <inheritdoc cref="MapProjector.ToMap(double[])"/>
public override float[] ToMap(double[] point)
/// <inheritdoc cref="MapProjector.ToMap(LvcPointD)"/>
public override LvcPoint ToMap(LvcPointD point)
{
var lat = point[1];
var lon = point[0];
var lat = point.Y;
var lon = point.X;

var latRad = lat * Math.PI / 180d;
var mercN = Math.Log(Math.Tan(Math.PI / 4d + latRad / 2d), Math.E);
var y = _h / 2d - _h * mercN / (2 * Math.PI);

return new[]
return new LvcPoint
{
// x' =
(float)((lon + 180) * (_w / 360d) + _ox),
X = (float)((lon + 180) * (_w / 360d) + _ox),

// y' =
(float) y + _oy
Y = (float) y + _oy
};
}
}
6 changes: 3 additions & 3 deletions src/skiasharp/LiveChartsCore.SkiaSharp/MapFactory.cs
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Expand Up @@ -106,10 +106,10 @@ public void GenerateLands(MapContext<SkiaSharpDrawingContext> context)

foreach (var point in landData.Coordinates)
{
var p = projector.ToMap(new double[] { point.X, point.Y });
var p = projector.ToMap(point);

var x = p[0];
var y = p[1];
var x = p.X;
var y = p.Y;

if (isFirst)
{
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