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将32位图像转换为黑白两色图像时出现问题

imaging image-processing vb.net wpf .net

1

user2719109 · 技术社区 · 11 年前

我有以下代码例程。。。

Public Shared Sub ConvertToBitonal(ByRef Source As System.Windows.Media.Imaging.WriteableBitmap)
    If Source.Format = System.Windows.Media.PixelFormats.BlackWhite Then
        Exit Sub
    End If

    Dim BytesPerPixel As Integer = (Source.Format.BitsPerPixel + 7) / 8
    Dim Stride As Integer = Source.PixelWidth * BytesPerPixel
    Dim NumBytes As Long = Source.PixelHeight * Stride
    Dim pixels As Byte() = New Byte(NumBytes - 1) {}

    Source.CopyPixels(pixels, Stride, 0)

    For cnt As Integer = 0 To pixels.Length - 1 Step BytesPerPixel
        Dim blue As Byte = pixels(cnt + 0)
        Dim green As Byte = pixels(cnt + 1)
        Dim red As Byte = pixels(cnt + 2)
        Dim intensity As Integer = CType(red, Integer) + CType(green, Integer) + CType(blue, Integer)
        Dim targetColor As Byte

        If intensity > 400 Then
            targetColor = 255
        Else
            targetColor = 0
        End If

        pixels(cnt + 0) = targetColor
        pixels(cnt + 1) = targetColor
        pixels(cnt + 2) = targetColor
        pixels(cnt + 3) = targetColor
    Next

    Source.WritePixels(New System.Windows.Int32Rect(0, 0, Source.PixelWidth, Source.PixelHeight), pixels, Stride, 0)
End Sub

当源图像是每像素24位时,输出完全符合我的要求,但当源图像为32位时,颜色就不稳定了,我得到了贯穿图像的垂直线。有人能告诉我如何修改例程,使32位图像像24位计数器部件一样显示出来吗?

这是我所说内容的屏幕截图。。。(显然我还没有足够的代表来发布图片,所以这里有一个链接

enter image description here

2 回复 | 直到 11 年前

1

0

Community CDub 8 年前

您可能需要先创建一个24bpp的映像副本。你试过了吗?

我很久以前也做过类似的事情(很久以前想不起细节了),这篇文章很有帮助: Bitonal conversion issues 。MSDN论坛上也有一些信息。

编辑: seen this entry?

2

0

Martin Tournoij ravi.zombie 8 年前

我仔细研究了代码,发现了问题:

Dim BytesPerPixel As Integer = (Source.Format.BitsPerPixel + 7) / 8

移除 + 7 .

同时更改此项:

    pixels(cnt + 0) = targetColor

    pixels(cnt + 1) = targetColor

    pixels(cnt + 2) = targetColor

    pixels(cnt + 3) = targetColor

到包含步骤的FOR循环。。。。。即。:

        Dim x%

        For x = cnt To cnt + BytesPerPixel - 1

            pixels(x) = targetColor

        Next

如果步骤是>4,它不会设置值,会给你这个向下的条。