使用 ASP.NET 进行图像调整大小

 

介绍  

有时，当我们上传图像并应用可变大小进行调整时，图像显示质量会下降。因此，本文将展示如何在不破坏图像质量的情况下调整图像大小。

背景 

在本文中，我们将使用一些绘图方法。
 

使用代码 

' Create new stream.
' Dim stream As New FileStream(fileName, FileMode.Open, FileAccess.Read)

' Create new image.
Dim image As System.Drawing.Image = System.Drawing.Image.FromStream(Stream)

' Calculate proportional max width and height.
Dim oldWidth As Integer = image.Width
Dim oldHeight As Integer = image.Height
If (CDec(oldWidth) / CDec(oldHeight)) > (CDec(newWidth) / CDec(newHeight)) Then
    Dim ratio As Decimal = CDec(newWidth) / oldWidth
    newHeight = CInt((oldHeight * ratio))
Else
    Dim ratio As Decimal = CDec(newHeight) / oldHeight
    newWidth = CInt((oldWidth * ratio))
End If

' Create a new bitmap with the same resolution as the original image.
Dim bitmap As New Bitmap(newWidth, newHeight, PixelFormat.Format24bppRgb)
bitmap.SetResolution(image.HorizontalResolution, image.VerticalResolution)

' Create a new graphic.
Dim graphics__1 As Graphics = Graphics.FromImage(bitmap)
graphics__1.Clear(Color.White)
graphics__1.InterpolationMode = InterpolationMode.HighQualityBicubic

' Create a scaled image based on the original.
graphics__1.DrawImage(image, New Rectangle(0, 0, newWidth, newHeight),
                      New Rectangle(0, 0, oldWidth, oldHeight), GraphicsUnit.Pixel)
                      graphics__1.Dispose()

 ' Save the scaled image.
 bitmap.Save(Server.MapPath("Images/") & strDestinationFileName, image.RawFormat)