public void ShlTest()
{
const int RepeatCount = 5;
UlongRandomGenerator random = new UlongRandomGenerator();
ulong[] y = new ulong[3];
ulong[] copy = new ulong[3];
int size = y.Length * 64;
for (int count = 0; count <= size; count++)
{
for (int pos = 0; pos < size - count; pos++)
{
for (int shift = 0; shift <= count; shift++)
{
for (int i = 0; i < RepeatCount; i++)
{
random.Generate(y.Length, y);
Vectors.Copy(y.Length, y, 0, copy, 0);
BitUtils.Shl(count, shift, y, pos);
// right part that was not copied
if (pos > 0)
{
Assert.IsTrue(BitUtils.Equals(pos, y, 0, copy, 0));
}
// shifted part
if (shift < count)
{
Assert.IsTrue(BitUtils.Equals(count - shift, y, pos + shift, copy, pos));
}
// zeroed part
if (shift > 0)
{
Assert.AreEqual(0, BitUtils.CountOneBits(shift, y, pos));
}
// left part that was not copied
if (pos + count < size)
{
Assert.IsTrue(BitUtils.Equals(size - (pos + count), y, pos + count, copy, pos + count));
}
}
}
}
}
}
public void SetBitsTest()
{
const int Size = 3 * 64;
ulong[] y = new ulong[3];
for (int count = 1; count < Size; count++)
{
for (int pos = 0; pos < Size - count; pos++)
{
y[0] = y[1] = y[2] = 0;
BitUtils.SetBits(count, y, pos);
Assert.AreEqual(count, BitUtils.CountOneBits(Size, y, 0));
Assert.AreEqual(pos, BitUtils.BitScanOneForward(Size, y, 0));
Assert.AreEqual(pos + count - 1, BitUtils.BitScanOneReverse(Size, y, Size - 1));
Assert.AreEqual(pos + count == Size ? -1 : pos + count, BitUtils.BitScanZeroForward(Size - pos, y, pos));
Assert.AreEqual(pos == 0 ? -1 : pos - 1, BitUtils.BitScanZeroReverse(pos + count, y, pos + count - 1));
}
}
}
/// <summary>
/// De-skews the <see cref="Image"/> and aligns it horizontally.
/// </summary>
/// <param name="dst">The destination <see cref="Image"/>. Can be <b>null</b>.</param>
/// <returns>
/// The destination <see cref="Image"/>.
/// </returns>
/// <exception cref="NotImplementedException">
/// <see cref="Image{T}.BitsPerPixel"/> is not one.
/// </exception>
/// <remarks>
/// <para>This method works with binary (1bpp) images only.</para>
/// </remarks>
public Image Deskew(Image dst)
{
if (this.BitsPerPixel != 1)
{
throw new NotImplementedException(Properties.Resources.E_UnsupportedDepth_1bpp);
}
int width = this.Width;
int height = this.Height;
int stride = this.Stride;
ulong[] bits = this.Bits;
// build histogram
ulong endMask = this.EndMask;
float[][] histogram = new float[stride][];
for (int ix = 0; ix < stride; ix++)
{
float[] h = histogram[ix] = new float[height];
ulong mask = ix == stride - 1 ? endMask : ulong.MaxValue;
for (int iy = 0, off = ix; iy < height; iy++, off += stride)
{
h[iy] = BitUtils.CountOneBits(bits[off] & mask);
}
}
// calculate image variance
float angleBest = 0.0f;
float varianceBest = EstimateSkewAngle(angleBest);
// move up or down with 1 degree interval
// move counterclockwise
for (float angle = -1.0f; angle >= -10.0f; angle -= 1.0f)
{
float variance = EstimateSkewAngle(angle);
if (variance <= varianceBest)
{
break;
}
varianceBest = variance;
angleBest = angle;
}
if (angleBest == 0.0f)
{
// move clockwise
for (float angle = 1.0f; angle <= 10.0f; angle += 1.0f)
{
float variance = EstimateSkewAngle(angle);
if (variance <= varianceBest)
{
break;
}
varianceBest = variance;
angleBest = angle;
}
}
// move up or down with 0.1 degree interval
// move counterclockwise
float originalAngle = angleBest;
for (float angle = angleBest - 0.1f, max = angleBest - 0.9f; angle >= max; angle -= 0.1f)
{
float variance = EstimateSkewAngle(angle);
if (variance <= varianceBest)
{
break;
}
varianceBest = variance;
angleBest = angle;
}
if (originalAngle == angleBest)
{
// move clockwise
for (float angle = angleBest + 0.1f, max = angleBest + 0.9f; angle <= max; angle += 0.1f)
{
float variance = EstimateSkewAngle(angle);
if (variance <= varianceBest)
{
break;
}
varianceBest = variance;
angleBest = angle;
}
}
return(this.Rotate(dst, -angleBest, BorderType.BorderRepl, 0));
float EstimateSkewAngle(float angle)
{
const float PiConv = 3.1415926535f / 180.0f;
int centerX = width / 2;
float dblTanA = (float)Math.Tan(angle * PiConv);
float[] ds = new float[height];
for (int ix = 0; ix < stride; ix++)
{
// negative shift is down
int shiftY = (dblTanA * (centerX - (ix * 64) - 32)).Round();
Mathematics.Add(
height - Math.Abs(shiftY),
histogram[ix],
shiftY < 0 ? 0 : shiftY,
ds,
shiftY < 0 ? -shiftY : 0);
}
return(ds.Variance());
}
}
