使用 VB.Net 合并大图像

Question

我希望有人能帮助我将几张大图像 (PNG) 合并为一张。我有多达 30 张 20000x2000 的图像，并且想合并它们。输出是可以加载到 GIS 软件中的图像。

我遇到的问题是我在第 4 张图片后内存不足。

我下面的代码在拼接时基本上将整个图像保存在内存中。有什么方法可以有效地拼接图像而不将其全部加载到内存中，或者增加内存余量并利用我所有的 RAM and/or 虚拟内存？

    Public Function stitchAllImagesOnXAxis(imageDirectoryPath As String, outputImagePath As String) As Boolean
    Try
        Dim evolvingImage As Bitmap
        Dim filenames() As String = IO.Directory.GetFiles(imageDirectoryPath)

        For i As Integer = 0 To filenames.Count - 1

            If Not filenames(i).EndsWith(".png") Then filenames = filenames.RemoveAt(i)

        Next i

        If filenames.Count = 0 Then Return False

        Dim FS As New IO.FileStream(filenames(0), IO.FileMode.Open)
        evolvingImage = Bitmap.FromStream(FS)
        FS.Close()



        For i As Integer = 1 To filenames.Count - 1

            FS = New IO.FileStream(filenames(i), IO.FileMode.Open)
            evolvingImage = stitchImagesOnXAxis(evolvingImage, Bitmap.FromStream(FS), 5)
            FS.Close()

        Next

        evolvingImage.Save(outputImagePath, Imaging.ImageFormat.Png)
        evolvingImage.Dispose()

        Return True
    Catch ex As Exception
        Debug.WriteLine(ex.Message)
        Return False
    End Try

Answer 1

 Public Function stitchAllImagesOnXAxisSO(imageDirectoryPath As String, outputImagePath As String, tolerance As Integer) As Boolean

    Try
        'blank 54 byte header for BMP
        Dim headerBytes() As Byte = blankHeader()

        'track the total width of the bmp for the header information
        Dim totalWidth As Integer = 0

        'the height of the BMP (assumes all images being joined are the same height)
        Dim height As Integer = 0

        'the files in the directory specified
        Dim filenames() As String = IO.Directory.GetFiles(imageDirectoryPath)

        'the filestream used to read each file
        Dim FS As IO.FileStream

        'a class to read the header information of the BMP files
        Dim dynamicHeaderInfo As BMPHeaderInformation

        'byte array to copy the bytes read to
        Dim copyBuffer() As Byte

        'ensure each file is a bmp file
        For i As Integer = 1 To filenames.Count - 1

            If Not filenames(i).EndsWith(".bmp") Then filenames = filenames.RemoveAt(i)

        Next i

        'if there isn't more than one image available then exit
        If filenames.Count < 2 Then Return False

        'if the output image exists than delete it
        If IO.File.Exists(outputImagePath) Then IO.File.Delete(outputImagePath)

        'and open it as new 
        Dim evolvingImageFS As New IO.FileStream(outputImagePath, IO.FileMode.OpenOrCreate)

        'write a blank header
        evolvingImageFS.Write(headerBytes, 0, headerBytes.Length)

        'set the height of the overall image (all images assumed the same height)
        dynamicHeaderInfo = New BMPHeaderInformation(filenames(0))
        height = dynamicHeaderInfo.width

        'writing one row at a time from one image at a time

        For row As Integer = 0 To height - 1

            For i As Integer = 0 To filenames.Count - 1

                'get the header data
                dynamicHeaderInfo = New BMPHeaderInformation(filenames(i))

                'open the file
                FS = New IO.FileStream(filenames(i), IO.FileMode.Open)



                'each time we are looking at the first row of an image add that width to the overall width
                If row = 0 Then totalWidth += dynamicHeaderInfo.width

                'set the position of the stream
                FS.Position = dynamicHeaderInfo.headerLength + (row * dynamicHeaderInfo.width * 3) + (row * dynamicHeaderInfo.rowPaddingLength)

                'set up the byte array to read in the bytes
                ReDim copyBuffer((dynamicHeaderInfo.width * 3) - 1)
                FS.Read(copyBuffer, 0, dynamicHeaderInfo.width * 3)
                'write the bytes to the new stream
                evolvingImageFS.Write(copyBuffer, 0, dynamicHeaderInfo.width * 3)

                'if we are at the last image and the total width is less than 500, write the trailing zeros on the row
                If i = filenames.Count - 1 Then padRowFromStream(totalWidth, evolvingImageFS)

                'close the stream
                FS.Close()
                FS.Dispose()

            Next

        Next

        'set the new header information
        setNewWidth(totalWidth, evolvingImageFS)
        setNewheight(height, evolvingImageFS)
        setNewImageFileSize(evolvingImageFS.Length, evolvingImageFS)
        setNewImageAreaSize(evolvingImageFS.Length - headerBytes.Length, evolvingImageFS)

        'close off the stream
        evolvingImageFS.Close()
        evolvingImageFS.Dispose()

        Return True
    Catch ex As Exception
        Debug.WriteLine(ex.Message)
        Return False
    End Try
End Function

对于任何感兴趣的人，我已经发布了我的解决方案。这对我来说效果很好，但可能需要针对个人用途进行一些调整。这也受限于 bmp 文件的理论限制为 16^8 字节。

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