Dec2017-Script-Dump/Pngcs/FilterWriteStrategy.cs

using System;

namespace Hjg.Pngcs
{
	// Token: 0x0200001C RID: 28
	internal class FilterWriteStrategy
	{
		// Token: 0x060000EA RID: 234 RVA: 0x00004B18 File Offset: 0x00002D18
		internal FilterWriteStrategy(ImageInfo imgInfo, FilterType configuredType)
		{
			this.imgInfo = imgInfo;
			this.configuredType = configuredType;
			if (configuredType < FilterType.FILTER_NONE)
			{
				if ((imgInfo.Rows < 8 && imgInfo.Cols < 8) || imgInfo.Indexed || imgInfo.BitDepth < 8)
				{
					this.currentType = FilterType.FILTER_NONE;
				}
				else
				{
					this.currentType = FilterType.FILTER_PAETH;
				}
			}
			else
			{
				this.currentType = configuredType;
			}
			if (configuredType == FilterType.FILTER_AGGRESSIVE)
			{
				this.discoverEachLines = FilterWriteStrategy.COMPUTE_STATS_EVERY_N_LINES;
			}
			if (configuredType == FilterType.FILTER_VERYAGGRESSIVE)
			{
				this.discoverEachLines = 1;
			}
		}

		// Token: 0x060000EB RID: 235 RVA: 0x00004BE6 File Offset: 0x00002DE6
		internal bool shouldTestAll(int rown)
		{
			if (this.discoverEachLines > 0 && this.lastRowTested + this.discoverEachLines <= rown)
			{
				this.currentType = FilterType.FILTER_UNKNOWN;
				return true;
			}
			return false;
		}

		// Token: 0x060000EC RID: 236 RVA: 0x00004C0C File Offset: 0x00002E0C
		internal void setPreference(double none, double sub, double up, double ave, double paeth)
		{
			this.preference = new double[] { none, sub, up, ave, paeth };
		}

		// Token: 0x060000ED RID: 237 RVA: 0x00004C3D File Offset: 0x00002E3D
		internal bool computesStatistics()
		{
			return this.discoverEachLines > 0;
		}

		// Token: 0x060000EE RID: 238 RVA: 0x00004C48 File Offset: 0x00002E48
		internal void fillResultsForFilter(int rown, FilterType type, double sum, int[] histo, bool tentative)
		{
			this.lastRowTested = rown;
			this.lastSums[(int)type] = sum;
			if (histo != null)
			{
				double num = ((rown == 0) ? 0.0 : 0.3);
				double num2 = 1.0 - num;
				double num3 = 0.0;
				for (int i = 0; i < 256; i++)
				{
					double num4 = (double)histo[i] / (double)this.imgInfo.Cols;
					num4 = this.histogram1[i] * num + num4 * num2;
					if (tentative)
					{
						num3 += ((num4 > 1E-08) ? (num4 * Math.Log(num4)) : 0.0);
					}
					else
					{
						this.histogram1[i] = num4;
					}
				}
				this.lastEntropies[(int)type] = -num3;
			}
		}

		// Token: 0x060000EF RID: 239 RVA: 0x00004D10 File Offset: 0x00002F10
		internal FilterType gimmeFilterType(int rown, bool useEntropy)
		{
			if (this.currentType == FilterType.FILTER_UNKNOWN)
			{
				if (rown == 0)
				{
					this.currentType = FilterType.FILTER_SUB;
				}
				else
				{
					double num = double.MaxValue;
					for (int i = 0; i < 5; i++)
					{
						double num2 = (useEntropy ? this.lastEntropies[i] : this.lastSums[i]);
						num2 /= this.preference[i];
						if (num2 <= num)
						{
							num = num2;
							this.currentType = (FilterType)i;
						}
					}
				}
			}
			if (this.configuredType == FilterType.FILTER_CYCLIC)
			{
				this.currentType = (this.currentType + 1) % (FilterType)5;
			}
			return this.currentType;
		}

		// Token: 0x04000088 RID: 136
		private static readonly int COMPUTE_STATS_EVERY_N_LINES = 8;

		// Token: 0x04000089 RID: 137
		private readonly ImageInfo imgInfo;

		// Token: 0x0400008A RID: 138
		private readonly FilterType configuredType;

		// Token: 0x0400008B RID: 139
		private FilterType currentType;

		// Token: 0x0400008C RID: 140
		private int lastRowTested = -1000000;

		// Token: 0x0400008D RID: 141
		private double[] lastSums = new double[5];

		// Token: 0x0400008E RID: 142
		private double[] lastEntropies = new double[5];

		// Token: 0x0400008F RID: 143
		private double[] preference = new double[] { 1.1, 1.1, 1.1, 1.1, 1.2 };

		// Token: 0x04000090 RID: 144
		private int discoverEachLines = -1;

		// Token: 0x04000091 RID: 145
		private double[] histogram1 = new double[256];
	}
}