public void ColorToOpaquePbgra32()
{
Assert.AreEqual(0xFF203040, BitmapUtility.ColorToOpaquePbgra32(
Color.FromArgb(0xFF, 0x20, 0x30, 0x40)));
Assert.AreEqual(0xFF203040, BitmapUtility.ColorToOpaquePbgra32(
Color.FromArgb(0x7F, 0x20, 0x30, 0x40)));
Assert.AreEqual(0xFF203040, BitmapUtility.ColorToOpaquePbgra32(
Color.FromArgb(0x00, 0x20, 0x30, 0x40)));
}
/// <summary>
/// Makes the specified <see cref="Color"/> transparent in the <see cref="BitmapBuffer"/>.
/// </summary>
/// <param name="color">
/// The <see cref="Color"/> to replace with transparent black.</param>
/// <remarks><para>
/// <b>MakeTransparent</b> sets all fully opaque <see cref="Pixels"/> of the specified
/// <paramref name="color"/> to zero, which is the <see cref="PixelFormats.Pbgra32"/>
/// equivalent of transparent black color. Partially transparent <see cref="Pixels"/> and
/// <see cref="Pixels"/> of any other color remain unchanged.
/// </para><para>
/// <b>MakeTransparent</b> ignores the alpha channel of the specified <paramref
/// name="color"/> and only replaces fully opaque <see cref="Pixels"/> because the
/// imprecision caused by the premultiplication of color channels in the <see
/// cref="PixelFormats.Pbgra32"/> format would otherwise produce false matches.
/// </para><note type="implementnotes">
/// The predefined <see cref="Colors.Transparent"/> color is transparent <em>white</em> (all
/// color channels maximized), not transparent <em>black</em> (all color channels zero).
/// That color is not representable in <see cref="PixelFormats.Pbgra32"/> format since all
/// color channel information of fully transparent color is lost.</note></remarks>
public void MakeTransparent(Color color)
{
uint value = BitmapUtility.ColorToOpaquePbgra32(color);
for (int i = 0; i < _pixels.Length; i++)
{
if (_pixels[i] == value)
{
_pixels[i] = 0u;
}
}
}
