vb.net减少图像文件大小与插值模式不工作。

Question

点击button1后，它给我test_reduce，文件大小为4.87 MB，原文件大小为1.91 MB，InterpolationMode完全不起作用......我想用InterpolationMode将文件大小从1.91 MB减少到1 MB以下。

原图。https:/images.alphacoders.com943943148.jpg

这是我的代码

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim jpg As Image = Image.FromFile("test.jpg")
        Dim tp As Bitmap = reduce(jpg, 1920, 1080)
        jpg.Dispose()
        jpg = tp
        jpg.Save("test_reduce.jpg")
    End Sub

    Private Function reduce(ByVal img As Image, ByVal width As Integer, ByVal height As Integer) As Image
        Dim imaf As New Bitmap(width, height)
        Dim pic As Graphics = Graphics.FromImage(imaf)
        pic.InterpolationMode = Drawing2D.InterpolationMode.Bicubic
        pic.DrawImage(img, 0, 0, width, height)
        Return imaf
    End Function

Answer 1

jpg.Save("test_reduce.jpg")

改为

jpg.Save("test_reduce.jpeg", Imaging.ImageFormat.Jpeg)