VB.net 简单的处理图片，黑白（类库——7）_vb.net 图像去背景

 我们看，这一张图片使我们用手机拍的图片，不经过处理，打印出来就是灰的

在Photoshop里可以通过调整色阶，选择黑色的再选择白色的，就可以清晰化了

 拍照时注意摊平，我这是扫描的彩色模式，作为测试

看VB.net如何处理 

本文参考的csdn大佬的文章，vb.net 教程 5-15 图像处理之内存处理6就改了一个参数

import：

Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.Runtime.InteropServices

写函数：value可以自己调节，不一定只是180

 ''' <summary>
    ''' 图片黑白处理，记得使用多线程调用函数
    ''' </summary>
    ''' <param name="value">黑白数值常量，建议从128开始调，范围为0~255(byte)</param>
    ''' <param name="bmp">要处理的图片</param>
    ''' <returns>处理后的图片</returns>
 
    Public Function BlackWhite(value As Byte, bmp As Bitmap)
        Dim destImg As New Bitmap(bmp.Width, bmp.Height)
        Dim sourceData As BitmapData = bmp.LockBits(New Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb)
        Dim destData As BitmapData = destImg.LockBits(New Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb)
        Dim pSource As IntPtr = sourceData.Scan0
        Dim allBytes As Integer = sourceData.Stride * sourceData.Height
        Dim rgbvalues() As Byte
        ReDim rgbvalues(allBytes - 1)
        Marshal.Copy(pSource, rgbvalues, 0, allBytes)
        Dim pos As Integer = 0
        Dim R, G, B As Integer
        Dim avgValue As Integer
        For j As Integer = 0 To sourceData.Height - 1
            For i As Integer = 0 To sourceData.Width - 1
                B = rgbvalues(pos)
                G = rgbvalues(pos + 1)
                R = rgbvalues(pos + 2)
                avgValue = (B + G + R) / 3
                If avgValue >= value Then avgValue = 255 Else avgValue = 0
                rgbvalues(pos) = avgValue
                rgbvalues(pos + 1) = avgValue
                rgbvalues(pos + 2) = avgValue
                pos += 3
            Next
            pos = pos + sourceData.Stride - sourceData.Width * 3
        Next
        Dim pDest As IntPtr = destData.Scan0
        Marshal.Copy(rgbvalues, 0, pDest, allBytes)
 
        bmp.UnlockBits(sourceData)
        destImg.UnlockBits(destData)
 
        Return destImg
 
    End Function

 调用：

 Private Sub Button6_Click(sender As Object, e As EventArgs) Handles Button6.Click
        Pic.Image = GDI.BlackWhite(180, New Bitmap("C:\Users\Administrator\Desktop\example.jpg"))
    End Sub

效果很好，可以去除一些褶皱，多余的背景