LocalHistogramEffect.cs

/////////////////////////////////////////////////////////////////////////////////
// Paint.NET                                                                   //
// Copyright (C) dotPDN LLC, Rick Brewster, Tom Jackson, and contributors.     //
// Portions Copyright (C) Microsoft Corporation. All Rights Reserved.          //
// See license-pdn.txt for full licensing and attribution details.             //
//                                                                             //
// Ported to Pinta by: Hanh Pham <hanh.pham@gmx.com>                           //
/////////////////////////////////////////////////////////////////////////////////

using System;

namespace Pinta.ImageManipulation.Effects
{
	public abstract class LocalHistogramEffect : BaseEffect
	{
		protected static int GetMaxAreaForRadius (int radius)
		{
			int area = 0;
			int cutoff = ((radius * 2 + 1) * (radius * 2 + 1) + 2) / 4;

			for (int v = -radius; v <= radius; ++v) {
				for (int u = -radius; u <= radius; ++u) {
					if (u * u + v * v <= cutoff) {
						++area;
					}
				}
			}

			return area;
		}

		private unsafe void SetToZero (int* pointer, uint size)
		{
			for (int i = 0; i < (size / sizeof (int)); i++) {
				*pointer = 0;
				pointer++;
			}
		}

		public virtual unsafe ColorBgra Apply (ColorBgra src, int area, int* hb, int* hg, int* hr, int* ha)
		{
			return src;
		}

		//same as Aply, except the histogram is alpha-weighted instead of keeping a separate alpha channel histogram.
		public virtual unsafe ColorBgra ApplyWithAlpha (ColorBgra src, int area, int sum, int* hb, int* hg, int* hr)
		{
			return src;
		}

		public static unsafe ColorBgra GetPercentile (int percentile, int area, int* hb, int* hg, int* hr, int* ha)
		{
			int minCount = area * percentile / 100;

			int b = 0;
			int bCount = 0;

			while (b < 255 && hb[b] == 0) {
				++b;
			}

			while (b < 255 && bCount < minCount) {
				bCount += hb[b];
				++b;
			}

			int g = 0;
			int gCount = 0;

			while (g < 255 && hg[g] == 0) {
				++g;
			}

			while (g < 255 && gCount < minCount) {
				gCount += hg[g];
				++g;
			}

			int r = 0;
			int rCount = 0;

			while (r < 255 && hr[r] == 0) {
				++r;
			}

			while (r < 255 && rCount < minCount) {
				rCount += hr[r];
				++r;
			}

			int a = 0;
			int aCount = 0;

			while (a < 255 && ha[a] == 0) {
				++a;
			}

			while (a < 255 && aCount < minCount) {
				aCount += ha[a];
				++a;
			}

			return ColorBgra.FromBgra ((byte)b, (byte)g, (byte)r, (byte)a);
		}

		public unsafe void RenderRect (int rad, ISurface src, ISurface dst, Rectangle rect)
		{
			int width = src.Width;
			int height = src.Height;

			int* leadingEdgeX = stackalloc int[rad + 1];
			int stride = src.Stride / sizeof (ColorBgra);

			// approximately (rad + 0.5)^2
			int cutoff = ((rad * 2 + 1) * (rad * 2 + 1) + 2) / 4;

			for (int v = 0; v <= rad; ++v) {
				for (int u = 0; u <= rad; ++u) {
					if (u * u + v * v <= cutoff) {
						leadingEdgeX[v] = u;
					}
				}
			}

			const int hLength = 256;
			int* hb = stackalloc int[hLength];
			int* hg = stackalloc int[hLength];
			int* hr = stackalloc int[hLength];
			int* ha = stackalloc int[hLength];
			uint hSize = (uint)(sizeof (int) * hLength);

			for (int y = rect.Top; y <= rect.Bottom; ++y) {
				SetToZero (hb, hSize);
				SetToZero (hg, hSize);
				SetToZero (hr, hSize);
				SetToZero (ha, hSize);

				int area = 0;

				ColorBgra* ps = src.GetPointAddress (rect.Left, y);
				ColorBgra* pd = dst.GetPointAddress (rect.Left, y);

				// assert: v + y >= 0
				int top = -Math.Min (rad, y);

				// assert: v + y <= height - 1
				int bottom = Math.Min (rad, height - 1 - y);

				// assert: u + x >= 0
				int left = -Math.Min (rad, rect.Left);

				// assert: u + x <= width - 1
				int right = Math.Min (rad, width - 1 - rect.Left);

				for (int v = top; v <= bottom; ++v) {
					ColorBgra* psamp = src.GetPointAddress (rect.Left + left, y + v);

					for (int u = left; u <= right; ++u) {
						if ((u * u + v * v) <= cutoff) {
							++area;
							++hb[psamp->B];
							++hg[psamp->G];
							++hr[psamp->R];
							++ha[psamp->A];
						}

						++psamp;
					}
				}

				for (int x = rect.Left; x <= rect.Right; x++) {
					*pd = Apply (*ps, area, hb, hg, hr, ha);

					// assert: u + x >= 0
					left = -Math.Min (rad, x);

					// assert: u + x <= width - 1
					right = Math.Min (rad + 1, width - 1 - x);

					// Subtract trailing edge top half
					int v = -1;

					while (v >= top) {
						int u = leadingEdgeX[-v];

						if (-u >= left) {
							break;
						}

						--v;
					}

					while (v >= top) {
						int u = leadingEdgeX[-v];
						ColorBgra* p = unchecked (ps + (v * stride)) - u;

						--hb[p->B];
						--hg[p->G];
						--hr[p->R];
						--ha[p->A];
						--area;

						--v;
					}

					// add leading edge top half
					v = -1;
					while (v >= top) {
						int u = leadingEdgeX[-v];

						if (u + 1 <= right) {
							break;
						}

						--v;
					}

					while (v >= top) {
						int u = leadingEdgeX[-v];
						ColorBgra* p = unchecked (ps + (v * stride)) + u + 1;

						++hb[p->B];
						++hg[p->G];
						++hr[p->R];
						++ha[p->A];
						++area;

						--v;
					}

					// Subtract trailing edge bottom half
					v = 0;

					while (v <= bottom) {
						int u = leadingEdgeX[v];

						if (-u >= left) {
							break;
						}

						++v;
					}

					while (v <= bottom) {
						int u = leadingEdgeX[v];
						ColorBgra* p = ps + v * stride - u;

						--hb[p->B];
						--hg[p->G];
						--hr[p->R];
						--ha[p->A];
						--area;

						++v;
					}

					// add leading edge bottom half
					v = 0;

					while (v <= bottom) {
						int u = leadingEdgeX[v];

						if (u + 1 <= right) {
							break;
						}

						++v;
					}

					while (v <= bottom) {
						int u = leadingEdgeX[v];
						ColorBgra* p = ps + v * stride + u + 1;

						++hb[p->B];
						++hg[p->G];
						++hr[p->R];
						++ha[p->A];
						++area;

						++v;
					}

					++ps;
					++pd;
				}
			}
		}

		//same as RenderRect, except the histogram is alpha-weighted instead of keeping a separate alpha channel histogram.
		public unsafe void RenderRectWithAlpha (int rad, ISurface src, ISurface dst, Rectangle rect)
		{
			int width = src.Width;
			int height = src.Height;

			int* leadingEdgeX = stackalloc int[rad + 1];
			int stride = src.Stride / sizeof (ColorBgra);

			// approximately (rad + 0.5)^2
			int cutoff = ((rad * 2 + 1) * (rad * 2 + 1) + 2) / 4;

			for (int v = 0; v <= rad; ++v) {
				for (int u = 0; u <= rad; ++u) {
					if (u * u + v * v <= cutoff) {
						leadingEdgeX[v] = u;
					}
				}
			}

			const int hLength = 256;
			int* hb = stackalloc int[hLength];
			int* hg = stackalloc int[hLength];
			int* hr = stackalloc int[hLength];
			uint hSize = (uint)(sizeof (int) * hLength);

			for (int y = rect.Top; y <= rect.Bottom; y++) {
				SetToZero (hb, hSize);
				SetToZero (hg, hSize);
				SetToZero (hr, hSize);

				int area = 0;
				int sum = 0;

				ColorBgra* ps = src.GetPointAddress (rect.Left, y);
				ColorBgra* pd = dst.GetPointAddress (rect.Left, y);

				// assert: v + y >= 0
				int top = -Math.Min (rad, y);

				// assert: v + y <= height - 1
				int bottom = Math.Min (rad, height - 1 - y);

				// assert: u + x >= 0
				int left = -Math.Min (rad, rect.Left);

				// assert: u + x <= width - 1
				int right = Math.Min (rad, width - 1 - rect.Left);

				for (int v = top; v <= bottom; ++v) {
					ColorBgra* psamp = src.GetPointAddress (rect.Left + left, y + v);

					for (int u = left; u <= right; ++u) {
						byte w = psamp->A;
						if ((u * u + v * v) <= cutoff) {
							++area;
							sum += w;
							hb[psamp->B] += w;
							hg[psamp->G] += w;
							hr[psamp->R] += w;
						}

						++psamp;
					}
				}

				for (int x = rect.Left; x <= rect.Right; x++) {
					*pd = ApplyWithAlpha (*ps, area, sum, hb, hg, hr);

					// assert: u + x >= 0
					left = -Math.Min (rad, x);

					// assert: u + x <= width - 1
					right = Math.Min (rad + 1, width - 1 - x);

					// Subtract trailing edge top half
					int v = -1;

					while (v >= top) {
						int u = leadingEdgeX[-v];

						if (-u >= left) {
							break;
						}

						--v;
					}

					while (v >= top) {
						int u = leadingEdgeX[-v];
						ColorBgra* p = unchecked (ps + (v * stride)) - u;
						byte w = p->A;

						hb[p->B] -= w;
						hg[p->G] -= w;
						hr[p->R] -= w;
						sum -= w;
						--area;

						--v;
					}

					// add leading edge top half
					v = -1;
					while (v >= top) {
						int u = leadingEdgeX[-v];

						if (u + 1 <= right) {
							break;
						}

						--v;
					}

					while (v >= top) {
						int u = leadingEdgeX[-v];
						ColorBgra* p = unchecked (ps + (v * stride)) + u + 1;
						byte w = p->A;

						hb[p->B] += w;
						hg[p->G] += w;
						hr[p->R] += w;
						sum += w;
						++area;

						--v;
					}

					// Subtract trailing edge bottom half
					v = 0;

					while (v <= bottom) {
						int u = leadingEdgeX[v];

						if (-u >= left) {
							break;
						}

						++v;
					}

					while (v <= bottom) {
						int u = leadingEdgeX[v];
						ColorBgra* p = ps + v * stride - u;
						byte w = p->A;

						hb[p->B] -= w;
						hg[p->G] -= w;
						hr[p->R] -= w;
						sum -= w;
						--area;

						++v;
					}

					// add leading edge bottom half
					v = 0;

					while (v <= bottom) {
						int u = leadingEdgeX[v];

						if (u + 1 <= right) {
							break;
						}

						++v;
					}

					while (v <= bottom) {
						int u = leadingEdgeX[v];
						ColorBgra* p = ps + v * stride + u + 1;
						byte w = p->A;

						hb[p->B] += w;
						hg[p->G] += w;
						hr[p->R] += w;
						sum += w;
						++area;

						++v;
					}

					++ps;
					++pd;
				}
			}
		}
	}
}