计算直方图的最小值和最大值

假设你的直方图值在 int[] 打电话 hist ,您可以使用一些LINQ扩展方法来查找最大的连续值组,并查找它们在数组中的开始和结束位置。如果你的柱状图只包含一个非零区域的所有零,并且不能很好地处理多个非零区域,那就太过分了——它只是选取了最长的水平跨度。

var histPos = hist
                .Select((hval, pos) => new { hval, pos })
                .GroupByWhile((prev,cur) => prev.hval != 0 && cur.hval != 0)
                .MaxBy(zvg => zvg.Count())
                .Select(zvg => zvg.pos);
var start = histPos.Min();
var end = histPos.Max();

我使用的扩展方法是 GroupByWhile 只要布尔lambda返回true,它就对连续对象进行分组,并且 MaxBy 返回lambda中返回值最大的对象。

public static class IEnumerableExt {
    // TKey combineFn((TKey Key, T Value) PrevKeyItem, T curItem):
    // PrevKeyItem.Key = Previous Key
    // PrevKeyItem.Value = Previous Item
    // curItem = Current Item
    // returns new Key
    public static IEnumerable<(TKey Key, T Value)> ScanPair<T, TKey>(this IEnumerable<T> src, TKey seedKey, Func<(TKey Key, T Value), T, TKey> combineFn) {
        using (var srce = src.GetEnumerator()) {
            if (srce.MoveNext()) {
                var prevkv = (seedKey, srce.Current);

                while (srce.MoveNext()) {
                    yield return prevkv;
                    prevkv = (combineFn(prevkv, srce.Current), srce.Current);
                }
                yield return prevkv;
            }
        }
    }

        // bool testFn(T prevItem, T curItem)
    // returns groups by sequential matching bool
    public static IEnumerable<IGrouping<int, T>> GroupByWhile<T>(this IEnumerable<T> src, Func<T, T, bool> testFn) =>
        src.ScanPair(1, (kvp, cur) => testFn(kvp.Value, cur) ? kvp.Key : kvp.Key + 1)
           .GroupBy(kvp => kvp.Key, kvp => kvp.Value);

    public static T MaxBy<T, TKey>(this IEnumerable<T> src, Func<T, TKey> keySelector, Comparer<TKey> keyComparer) => src.Aggregate((a, b) => keyComparer.Compare(keySelector(a), keySelector(b)) > 0 ? a : b);
    public static T MaxBy<T, TKey>(this IEnumerable<T> src, Func<T, TKey> keySelector) => src.Aggregate((a, b) => Comparer<TKey>.Default.Compare(keySelector(a), keySelector(b)) > 0 ? a : b);    
}

如果我理解正确的话,你可以把像素作为一个sbyte数组, 在这种情况下,这对我很有效:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleMinMax
{
    class Program
    {
        static void Main(string[] args)
        {
            sbyte[] array1 = { 1, -1, -2, 0, 99, -111 };

            MinMax(array1);

            void MinMax(sbyte[] array)
            {
                // Report minimum and maximum values.
                Console.WriteLine("max = {0}; min = {1}", array.Max(), array.Min());
            }
        }
    }
}