Question

我希望在将图像上传到本地存储之前调整图像的分辨率。现在它以完整的分辨率保存图像，我必须使用width="200" height="200"或aspx中的css标记手动调整图像大小。我想在存储之前减小图像的文件大小，因此当用户通过按钮上传图像分辨率时，可以调整图像分辨率。我之前尝试过使用System.Drawing并将int imageHeight和int maxWidth设置为调整大小但似乎无法使其工作。

任何人都知道如何做到这一点？

到目前为止我的代码是：

Protected Sub btn_SavePic_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btn_SavePic.Click
    Dim newFileName As String
    Dim SqlString As String
    If fup_Picture.HasFile Then
        Dim myGUID = Guid.NewGuid()
        newFileName = myGUID.ToString() & ".jpg"
        Dim fileLocationOnServerHardDisk = Request.MapPath("Picture") & "/" & newFileName
        fup_Picture.SaveAs(fileLocationOnServerHardDisk)
    End If

Answer 1

您不需要先将文件保存到磁盘，也可以在内存中调整大小。我使用类似于以下的代码来调整上传到相册的图像的大小。 HttpPostedFile对象具有一个InputStream属性，可以让您获得实际的流。 toStream允许您将输出流式传输到您想要的任何内容（响应，文件等）。它将确保图像正确缩放以适合最大640宽或480高的盒子。您可能希望将它们放在配置文件中而不是硬编码。

private void ResizeImage( Stream fromStream, Stream toStream )
{
    const double maxWidth = 640;
    const double maxHeight = 480;

    using( Image image = Image.FromStream( fromStream ) )
    {
        double widthScale = 1;

        if( image.Width > maxWidth )
        {
            widthScale = maxWidth / image.Width;
        }

        double heightScale = 1;

        if( image.Height > maxHeight )
        {
            heightScale = maxHeight / image.Height;
        }

        if( widthScale < 1 || heightScale < 1 )
        {
            double scaleFactor = widthScale < heightScale ? widthScale : heightScale;

            int newWidth = (int)(image.Width * scaleFactor);
            int newHeight = (int)(image.Height * scaleFactor);
            using( Bitmap thumbnailBitmap = new Bitmap( newWidth, newHeight ) )
            {
                using( Graphics thumbnailGraph = Graphics.FromImage( thumbnailBitmap ) )
                {
                    thumbnailGraph.CompositingQuality = CompositingQuality.HighQuality;
                    thumbnailGraph.SmoothingMode = SmoothingMode.HighQuality;
                    thumbnailGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;

                    Rectangle imageRectangle = new Rectangle( 0, 0, newWidth, newHeight );
                    thumbnailGraph.DrawImage( image, imageRectangle );

                    ImageCodecInfo jpegCodec = ImageCodecInfo.GetImageEncoders()
                        .FirstOrDefault( c => c.FormatDescription == "JPEG" );
                    if( jpegCodec != null )
                    {
                        EncoderParameters encoderParameters = new EncoderParameters( 1 );
                        encoderParameters.Param[0] = new EncoderParameter( Encoder.Quality, 100L );

                        thumbnailBitmap.Save( toStream, jpegCodec, encoderParameters );
                    }
                    else
                    {
                        thumbnailBitmap.Save( toStream, ImageFormat.Jpeg );
                    }
                }
            }
        }
        else
        {
            image.Save( toStream, ImageFormat.Jpeg );
        }
    }
}

在vb中上载之前调整图像大小

1 个答案: