/// <summary>
/// Reduces the size and resolution of this <see cref="Image"/> by a factor of 4 by downsampling.
/// </summary>
/// <param name="dst">The destination <see cref="Image"/>. Can be <b>null</b>.</param>
/// <returns>
/// The destination <see cref="Image"/>.
/// </returns>
/// <remarks>
/// <para>If <paramref name="dst"/> is <b>null</b> the method creates new destination <see cref="Image"/> with dimensions of this <see cref="Image"/>.</para>
/// <para>If <paramref name="dst"/> equals this <see cref="Image"/>, the operation is performed in-place.</para>
/// <para>Conversely, the <paramref name="dst"/> is reallocated to the dimensions of this <see cref="Image"/>.</para>
/// </remarks>
public Image ScaleByDownsampling4(Image dst)
{
int width = this.Width;
int height = this.Height;
int bitsPerPixel = this.BitsPerPixel;
int dstwidth = width / 4;
int dstheight = height / 4;
bool inplace = dst == this;
dst = this.CreateTemplate(dst, dstwidth, dstheight, bitsPerPixel);
switch (bitsPerPixel)
{
case 1:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
ulong * ptrsrc = (ulong *)bitssrc;
ushort *ptrdst = (ushort *)bitsdst;
int stridesrc = this.Stride;
int stride16dst = dst.Stride * 4;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stridesrc, ptrdst += stride16dst)
{
for (int x = 0, xdst = 0, xsrc = 0; x < dstwidth; x += 16, xdst++, xsrc++)
{
ulong bits = ptrsrc[xsrc];
ptrdst[xdst] = (ushort)(
(bits & 0x0001) |
((bits >> 3) & 0x0002) |
((bits >> 6) & 0x0004) |
((bits >> 9) & 0x0008) |
((bits >> 12) & 0x0010) |
((bits >> 15) & 0x0020) |
((bits >> 18) & 0x0040) |
((bits >> 21) & 0x0080) |
((bits >> 24) & 0x0100) |
((bits >> 27) & 0x0200) |
((bits >> 30) & 0x0400) |
((bits >> 33) & 0x0800) |
((bits >> 36) & 0x1000) |
((bits >> 39) & 0x2000) |
((bits >> 42) & 0x4000) |
((bits >> 45) & 0x8000));
}
}
}
}
break;
case 2:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
ulong * ptrsrc = (ulong *)bitssrc;
ushort *ptrdst = (ushort *)bitsdst;
int stridesrc = this.Stride;
int stride16dst = dst.Stride * 4;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stridesrc, ptrdst += stride16dst)
{
for (int x = 0, xdst = 0, xsrc = 0; x < dstwidth; x += 8, xdst++, xsrc++)
{
ulong bits = ptrsrc[xsrc];
ptrdst[xdst] = (ushort)(
(bits & 0x0003) |
((bits >> 6) & 0x000c) |
((bits >> 12) & 0x0030) |
((bits >> 18) & 0x00c0) |
((bits >> 24) & 0x0300) |
((bits >> 30) & 0x0c00) |
((bits >> 36) & 0x3000) |
((bits >> 42) & 0xc000));
}
}
}
}
break;
case 4:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
ulong * ptrsrc = (ulong *)bitssrc;
ushort *ptrdst = (ushort *)bitsdst;
int stridesrc = this.Stride;
int stride16dst = dst.Stride * 4;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stridesrc, ptrdst += stride16dst)
{
for (int x = 0, xdst = 0, xsrc = 0; x < dstwidth; x += 4, xdst++, xsrc++)
{
ulong bits = ptrsrc[xsrc];
ptrdst[xdst] = (ushort)(
(bits & 0x000f) |
((bits >> 12) & 0x00f0) |
((bits >> 24) & 0x0f00) |
((bits >> 36) & 0xf000));
}
}
}
}
break;
case 8:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
byte *ptrsrc = (byte *)bitssrc;
byte *ptrdst = (byte *)bitsdst;
int stride8src = this.Stride8;
int stride8dst = dst.Stride8;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stride8src, ptrdst += stride8dst)
{
for (int xdst = 0, xsrc = 0; xdst < dstwidth; xdst++, xsrc += 4)
{
ptrdst[xdst] = ptrsrc[xsrc];
}
}
}
}
break;
case 16:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
ushort *ptrsrc = (ushort *)bitssrc;
ushort *ptrdst = (ushort *)bitsdst;
int stride16src = this.Stride * 4;
int stride16dst = dst.Stride * 4;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stride16src, ptrdst += stride16dst)
{
for (int xdst = 0, xsrc = 0; xdst < dstwidth; xdst++, xsrc += 4)
{
ptrdst[xdst] = ptrsrc[xsrc];
}
}
}
}
break;
case 24:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
byte *ptrsrc = (byte *)bitssrc;
byte *ptrdst = (byte *)bitsdst;
int stride8src = this.Stride8;
int stride8dst = dst.Stride8;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stride8src, ptrdst += stride8dst)
{
for (int xdst = 0, xsrc = 0; xdst < 3 * dstwidth; xdst += 3, xsrc += 4 * 3)
{
ptrdst[xdst + 0] = ptrsrc[xsrc + 0];
ptrdst[xdst + 1] = ptrsrc[xsrc + 1];
ptrdst[xdst + 2] = ptrsrc[xsrc + 2];
}
}
}
}
break;
case 32:
unsafe
{
fixed(ulong *bitssrc = this.Bits, bitsdst = dst.Bits)
{
uint *ptrsrc = (uint *)bitssrc;
uint *ptrdst = (uint *)bitsdst;
int stride32src = this.Stride * 2;
int stride32dst = dst.Stride * 2;
for (int ydst = 0; ydst < dstheight; ydst++, ptrsrc += 4 * stride32src, ptrdst += stride32dst)
{
for (int xdst = 0, xsrc = 0; xdst < dstwidth; xdst++, xsrc += 4)
{
ptrdst[xdst] = ptrsrc[xsrc];
}
}
}
}
break;
default:
throw new NotSupportedException(string.Format(
CultureInfo.InvariantCulture,
Properties.Resources.E_UnsupportedDepth,
bitsPerPixel));
}
dst.SetResolution(this.HorizontalResolution / 4, this.VerticalResolution / 4);
dst.AppendTransform(new MatrixTransform(0.25, 0.25));
if (inplace)
{
this.Attach(dst);
return(this);
}
return(dst);
}
