/// <inheritdoc />
public Bitmap Filter(Bitmap src)
{
if (src is null)
{
throw new ArgumentNullException(nameof(src));
}
if (src.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new NotSupportedException(Errors.NotSupported);
}
var bitmapData = src.LockBits(
new Rectangle(0, 0, src.Width, src.Height),
ImageLockMode.ReadWrite, src.PixelFormat);
var(width, height) = (src.Width, src.Height);
var options = new ParallelOptions()
{
MaxDegreeOfParallelism = Environment.ProcessorCount
};
var step = Image.GetPixelFormatSize(PixelFormat.Format32bppArgb) / 8;
unsafe
{
var startPtr = (byte *)bitmapData.Scan0.ToPointer();
var stride = bitmapData.Stride;
Parallel.For(0, height, options, y =>
{
//get the address of a row
var ptr = startPtr + y * stride;
for (int x = 0; x < width; ++x, ptr += step)
{
ptr[0] = ptr[1] = ptr[2] = (byte)_rec.GetLuma(
ref ptr[2], ref ptr[1], ref ptr[0]);
}
});
}
src.UnlockBits(bitmapData);
return(src);
}
/// <inheritdoc />
public Bitmap Filter(Bitmap src)
{
if (src is null)
{
throw new ArgumentNullException(nameof(src));
}
if (src.PixelFormat != PixelFormat.Format32bppArgb)
{
throw new NotSupportedException(Errors.NotSupported);
}
var bitmapData = src.LockBits(
new Rectangle(0, 0, src.Width, src.Height),
ImageLockMode.ReadWrite, src.PixelFormat);
var(width, height) = (src.Width, src.Height);
var options = new ParallelOptions()
{
MaxDegreeOfParallelism = Environment.ProcessorCount
};
var step = Image.GetPixelFormatSize(PixelFormat.Format32bppArgb) / 8;
unsafe
{
var startPtr = (byte *)bitmapData.Scan0.ToPointer();
var stride = bitmapData.Stride;
var bag = new ConcurrentBag <double>();
//get N luminance partial sums
Parallel.For(0, height, options, () => 0.0, (y, state, partial) =>
{
var ptr = startPtr + y * stride;
for (var x = 0; x < width; ++x, ptr += step)
{
partial += _rec.GetLuma(
ref ptr[2], ref ptr[1], ref ptr[0]
);
}
return(partial);
},
(x) => bag.Add(x));
//get luminance average
var average = bag.Sum() / (width * height);
Parallel.For(0, height, options, y =>
{
var ptr = startPtr + y * stride;
for (var x = 0; x < width; ++x, ptr += step)
{
//if relative luminance greater or equal than average
//set it to white
if (_rec.GetLuma(ref ptr[2], ref ptr[1], ref ptr[0]) >= average)
{
ptr[0] = ptr[1] = ptr[2] = 255;
}
//else to black
else
{
ptr[0] = ptr[1] = ptr[2] = 0;
}
}
});
}
src.UnlockBits(bitmapData);
return(src);
}