/// <summary>
/// Changes the way alpha and color values are stored.
/// Optionally, all exisiting vertices are updated.
/// </summary>
public void SetPremultipliedAlpha(bool value, bool updateVertices)
{
if (value == _premultipliedAlpha)
{
return;
}
if (updateVertices)
{
if (value)
{
for (int i = 0; i < _numVertices; ++i)
{
_vertexColors[i] = VertexColorHelper.PremultiplyAlpha(_vertexColors[i]);
}
}
else
{
for (int i = 0; i < _numVertices; ++i)
{
_vertexColors[i] = VertexColorHelper.UnmultiplyAlpha(_vertexColors[i]);
}
}
}
_premultipliedAlpha = value;
}
/// <summary>
/// Multiplies a range of alpha values with a certain factor.
/// </summary>
public void ScaleAlphaBy(float factor, int index, int numVertices)
{
if (index < 0 || index >= _numVertices)
{
throw new IndexOutOfRangeException("Invalid vertex index");
}
if (factor == 1.0f)
{
return;
}
int minAlpha = _premultipliedAlpha ? (int)(MIN_ALPHA * 255.0f) : 0;
for (int i = index; i < index + numVertices; ++i)
{
VertexColor vertexColor = _vertexColors[i];
byte newAlpha = Convert.ToByte(NumberUtil.Clamp(vertexColor.A * factor, minAlpha, 255));
if (_premultipliedAlpha)
{
vertexColor = VertexColorHelper.UnmultiplyAlpha(vertexColor);
vertexColor.A = newAlpha;
_vertexColors[i] = VertexColorHelper.PremultiplyAlpha(vertexColor);
}
else
{
_vertexColors[i] = VertexColorHelper.CreateVertexColor(vertexColor.R, vertexColor.G, vertexColor.B, newAlpha);
}
}
}
/// <summary>
/// Updates the color of a vertex. The method always expects non-premultiplied alpha values.
/// </summary>
public void SetColor(uint color, float alpha, int atIndex)
{
if (atIndex < 0 || atIndex >= _numVertices)
{
throw new IndexOutOfRangeException("Invalid vertex index");
}
alpha = NumberUtil.Clamp(alpha, _premultipliedAlpha ? MIN_ALPHA : 0.0f, 1.0f);
VertexColor vertexColor = VertexColorHelper.CreateVertexColor(color, alpha);
_vertexColors[atIndex] = _premultipliedAlpha ? VertexColorHelper.PremultiplyAlpha(vertexColor) : vertexColor;
}
/// <summary>
/// Returns the RGB color of a vertex (without premultiplied alpha).
/// </summary>
public uint ColorAt(int index)
{
if (index < 0 || index >= _numVertices)
{
throw new IndexOutOfRangeException("Invalid vertex index");
}
VertexColor vertexColor = _vertexColors[index];
if (_premultipliedAlpha)
{
vertexColor = VertexColorHelper.UnmultiplyAlpha(vertexColor);
}
return(ColorUtil.GetRGB(vertexColor.R, vertexColor.G, vertexColor.B));
}
