判断一幅图片是否是黑色，灰度直方图

判断一幅图片是否是黑色的，通过灰度直方图，颜色直方图或图像亮度等方法可以实现

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Imaging;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        public Bitmap bmpobj;
        private void Form1_Load(object sender, EventArgs e)
        {
            string path = Application.StartupPath + @"\33.jpg";
            pictureBox1.Image = Image.FromFile(path); 

            bmpobj = new Bitmap(Application.StartupPath + @"\33.jpg");
            //bmpobj = new Bitmap(pic);    //转换为Format32bppRgb
        }


        /// <summary>
        /// 根据RGB，计算灰度值
        /// </summary>
        /// <param name="posClr">Color值</param>
        /// <returns>灰度值，整型</returns>
        private int GetGrayNumColor(System.Drawing.Color posClr)
        {
            return (posClr.R * 19595 + posClr.G * 38469 + posClr.B * 7472) >> 16;
        }
 
        /// <summary>
        /// 灰度转换,逐点方式
        /// </summary>
        public void GrayByPixels()
        {
            int totalNum = 0;
            int totalGrayPix = 0;

            for (int i = 0; i < bmpobj.Height; i++)
            {
                for (int j = 0; j < bmpobj.Width; j++)
                {
                    int tmpValue = GetGrayNumColor(bmpobj.GetPixel(j, i));
                    totalNum += 1;
                    totalGrayPix += tmpValue; 
                    
                    //反转
                    //bmpobj.SetPixel(j, i, Color.FromArgb(tmpValue, tmpValue, tmpValue));
                }
            }

            //判断是否是黑色图片：0=全黑，255=全白；这种方法不是很准的，效率也不是很高
            //取各个像素的平均值
            int avgGray = totalGrayPix / totalNum;
            if (avgGray < 50)
            {
                MessageBox.Show("像素灰度平均值：" + avgGray.ToString() + ",认为是黑色或接近黑色");
            }
            else
            {
                MessageBox.Show("彩色图像");
            }

        }

        private void button1_Click(object sender, EventArgs e)
        {
            GrayByPixels();
        }
         

    }
}