在不保存新图像的情况下将图像调整大小并将其压缩为字节数组 [英] Resize and Compress image to byte array without saving the new image

问题描述

图像首先被调整大小，压缩，然后作为Preview.jpg"保存在磁盘上，然后打开它转换为字节数组.代码工作正常，但如果不将图像保存在磁盘上，我无法弄清楚如何做到这一点.

The image is first resized, compressed and then saved on disk as "Preview.jpg" and then it is opened to convert into byte array. The code works fine but I cannot figure out how to do it without saving the image on disk.

代码如下:

Public Function GetThumb_Preview(ByVal sourceImg As String) As Byte()

    Dim jgpEncoder As ImageCodecInfo = GetEncoder(ImageFormat.Jpeg)
    Dim myEncoder As System.Drawing.Imaging.Encoder = System.Drawing.Imaging.Encoder.Quality
    Dim myEncoderParameters As New EncoderParameters(1)
    Dim myEncoderParameter As New EncoderParameter(myEncoder, 50&)
    myEncoderParameters.Param(0) = myEncoderParameter

    Dim myBitmap As New Bitmap(sourceImg)

    Dim oWidth As Integer = myBitmap.Width
    Dim oHeight As Integer = myBitmap.Height

    Dim aspectRatio As Double = oHeight / oWidth

    Dim thumbWidthDouble As Double = 200
    Dim thumbHeightDouble As Double = Math.Round(thumbWidthDouble * aspectRatio)

    Dim thumbWidth As Integer = CInt(thumbWidthDouble)
    Dim thumbHeight As Integer = CInt(thumbHeightDouble)

    Dim myThumb As New Bitmap(myBitmap, thumbWidth, thumbHeight)

    Dim targetPreviewPath As String = "E:\Preview.jpg"

    myThumb.Save(targetPreviewPath, jgpEncoder, myEncoderParameters)

    Dim myImage As Image = Image.FromFile(targetPreviewPath)

    Dim imgByteArray As Byte() = Nothing

    'Image to byte[]      
    Dim imgMemoryStream As MemoryStream = New MemoryStream()
    myImage.Save(imgMemoryStream, System.Drawing.Imaging.ImageFormat.Jpeg)
    imgByteArray = imgMemoryStream.GetBuffer()

    Return imgByteArray

End Function

推荐答案

那就是变数多，做的少.您还有许多未处理的对象.只有当生成的字节数据小于缓冲区大小时，它才会返回一个有效的字节数组.它在这种情况下有效，因为您将大小调整为 200 倍并降低质量.

That is a lot of variables to do so little. You also have a number of objects not being disposed. It will also return a valid Byte array only when the resulting byte data is less than the buffer size. It works in this case because you are resizing to 200x and reducing quality.

我没有测试我是否正确折叠了所有这些变量，但应该非常接近.更重要的是处理你创建的东西，并获得所有的字节返回:

I didnt test if I collapsed all those variables correctly, but should be very close. More important is disposing things you create, and getting the all the Bytes for the return:

Dim jgpEncoder As ImageCodecInfo = GetEncoder(ImageFormat.Jpeg)
Dim myEncoder As System.Drawing.Imaging.Encoder = 
          System.Drawing.Imaging.Encoder.Quality
Dim myEncoderParameters As New EncoderParameters(1)
Dim myEncoderParameter As New EncoderParameter(myEncoder, 50&)
myEncoderParameters.Param(0) = myEncoderParameter

Dim imgByteArray As Byte()

Using myBitmap As New Bitmap(sourceImg)    ' i guess this is from file

    Dim aspectRatio As Double = myBitmap.Height / myBitmap.Width

    ' USING for disposable objects
    Using myThumb As New Bitmap(myBitmap, 200, 
                                CInt(Math.Round(200 * aspectRatio))),
        ms As New MemoryStream

        ' encode image to memstream
        myThumb.Save(ms, jgpEncoder, myEncoderParameters)

        ' rewind and get ALL bytes for the new image
        ms.Position = 0
        imgByteArray = ms.ToArray

    End Using
End Using           ' dispose

Return imgByteArray

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