asp.net – 调整白色图像后获得灰色边框

我正在搜索谷歌的某种解决方案,我发现了一个,我试图在我的代码中实现它,但它不起作用.问题是,在调整白色图像大小后,它们会变成灰色边框.

这是我找到的soloution的链接：

它说：
出现此问题的原因是您正在将图像数据插值为
新的大小,但沿着边缘没有像素插值和.NET
默认情况下,这些边使用黑色像素.要解决此问题,您需要使用
DrawImage调用中的ImageAttributes类….

https://groups.google.com/group/microsoft.public.dotnet.framework.drawing/browse_thread/thread/d834851b49274fd9/81a4fd43694457ac?hl=en&lnk=st&q=DrawImage+resized+border#81a4fd43694457ac

代码1：这是我的代码实现ImageAttributes：

Private Shared Function ResizeImageFile(ByVal imageFile As Byte(),ByVal targetSize As Integer) As Byte()

    Using oldImage As System.Drawing.Image = System.Drawing.Image.FromStream(New MemoryStream(imageFile))

        Dim newSize As Size = CalculateDimensions(oldImage.Size,targetSize)

        Using newImage As New Bitmap(newSize.Width,newSize.Height,PixelFormat.Format32bppRgb)

            Using canvas As Graphics = Graphics.FromImage(newImage)

                Using ia As New ImageAttributes

                    ia.SetWrapMode(Drawing2D.WrapMode.TileFlipXY)
                    canvas.SmoothingMode = SmoothingMode.AntiAlias
                    canvas.InterpolationMode = InterpolationMode.HighQualityBicubic
                    canvas.PixelOffsetMode = PixelOffsetMode.HighQuality
                    canvas.DrawImage(oldImage,New Rectangle(New Point(0,0),newSize),newImage.Width,newImage.Height,GraphicsUnit.Pixel,ia)

                    Dim m As New MemoryStream()

                    newImage.Save(m,ImageFormat.Png)
                    Return m.GetBuffer()

                End Using

            End Using

        End Using

    End Using

End Function

Private Shared Function CalculateDimensions(ByVal oldSize As Size,ByVal targetSize As Integer) As Size

    Dim newSize As New Size()

    If oldSize.Height > oldSize.Width Then

        newSize.Width = CInt((oldSize.Width * (CSng(targetSize) / CSng(oldSize.Height))))
        newSize.Height = targetSize

    Else

        newSize.Width = targetSize
        newSize.Height = CInt((oldSize.Height * (CSng(targetSize) / CSng(oldSize.Width))))

    End If

    Return newSize

End Function

代码2：在白色图像上涂抹灰色边框的代码

这是调整大小后的图像：

新图像尺寸宽度= 400px

Private Shared Function ResizeImageFile(ByVal imageFile As Byte(),PixelFormat.Format32bppRgb)

            Using canvas As Graphics = Graphics.FromImage(newImage)

                    canvas.SmoothingMode = SmoothingMode.AntiAlias
                    canvas.InterpolationMode = InterpolationMode.HighQualityBicubic
                    canvas.PixelOffsetMode = PixelOffsetMode.HighQuality
                    canvas.DrawImage(oldImage,newSize))

                    Dim m As New MemoryStream()

                    newImage.Save(m,ImageFormat.Png)
                    Return m.GetBuffer()

            End Using

        End Using

    End Using

End Function

Private Shared Function CalculateDimensions(ByVal oldSize As Size,ByVal targetSize As Integer) As Size

    Dim newSize As New Size()

    If oldSize.Height > oldSize.Width Then

        newSize.Width = CInt((oldSize.Width * (CSng(targetSize) / CSng(oldSize.Height))))
        newSize.Height = targetSize

    Else

        newSize.Width = targetSize
        newSize.Height = CInt((oldSize.Height * (CSng(targetSize) / CSng(oldSize.Width))))

    End If

    Return newSize

End Function

更新30.07.2011：

CODE 1解决了白色图像上灰色边框的问题,但是存在新问题.问题出在这行代码中：

canvas.DrawImage(oldImage,ia)

使用此代码,我得到具有所需宽度和高度的输出图像,没有灰色边框,但oldImage没有缩放.

例如：

如果我想上传,调整大小并保存有形的图像,例如640x480px,而targetSize是400px.作为输出,我得到一个宽度为400px,高度：300px的图像,但oldImage没有调整大小/缩放到400px.在这种情况下,oldImage以原始分辨率绘制.如何缩放oldImage以正确绘制？有人能指出我正确的解决方案或修改代码吗？

对每个人而言,但我找到了解决所有问题的方法.

由于以下代码行,CODE 1无法正常工作：

canvas.DrawImage(oldImage,ia)

解：

canvas.DrawImage(oldImage,oldImage.Width,oldImage.Height,ia)

这是完整的工作代码(没有灰色/黑色边框的调整大小的图像)：

Private Shared Function ResizeImageFile(ByVal imageFile As Byte(),ByVal targetSize As Integer) As Size

    Dim newSize As New Size()

    If oldSize.Height > oldSize.Width Then

        newSize.Width = CInt((oldSize.Width * (CSng(targetSize) / CSng(oldSize.Height))))
        newSize.Height = targetSize

    Else

        newSize.Width = targetSize
        newSize.Height = CInt((oldSize.Height * (CSng(targetSize) / CSng(oldSize.Width))))

    End If

    Return newSize

End Function

public void ResizeImage(HttpPostedFile fil,string sPhysicalPath,string sOrgFileName,string sThumbNailFileName,ImageFormat oFormat,int rez)
{

    try
    {

        System.Drawing.Image oImg = System.Drawing.Image.FromStream(fil.InputStream);

        decimal pixtosubstract = 0;
        decimal percentage;

        //default
        Size ThumbNailSizeToUse = new Size();
        if (ThumbNailSize.Width < oImg.Size.Width || ThumbNailSize.Height < oImg.Size.Height)
        {
            if (oImg.Size.Width > oImg.Size.Height)
            {
                percentage = (((decimal)oImg.Size.Width - (decimal)ThumbNailSize.Width) / (decimal)oImg.Size.Width);
                pixtosubstract = percentage * oImg.Size.Height;
                ThumbNailSizeToUse.Width = ThumbNailSize.Width;
                ThumbNailSizeToUse.Height = oImg.Size.Height - (int)pixtosubstract;
            }
            else
            {
                percentage = (((decimal)oImg.Size.Height - (decimal)ThumbNailSize.Height) / (decimal)oImg.Size.Height);
                pixtosubstract = percentage * (decimal)oImg.Size.Width;
                ThumbNailSizeToUse.Height = ThumbNailSize.Height;
                ThumbNailSizeToUse.Width = oImg.Size.Width - (int)pixtosubstract;
            }

        }
        else
        {
            ThumbNailSizeToUse.Width = oImg.Size.Width;
            ThumbNailSizeToUse.Height = oImg.Size.Height;
        }

        Bitmap bmp = new Bitmap(ThumbNailSizeToUse.Width,ThumbNailSizeToUse.Height);
        bmp.SetResolution(rez,rez);
        System.Drawing.Image oThumbNail = bmp;

        bmp = null;

        Graphics oGraphic = Graphics.FromImage(oThumbNail);

        oGraphic.CompositingQuality = CompositingQuality.HighQuality;

        oGraphic.SmoothingMode = SmoothingMode.HighQuality;

        oGraphic.InterpolationMode = InterpolationMode.HighQualityBicubic;

        Rectangle oRectangle = new Rectangle(0,ThumbNailSizeToUse.Width,ThumbNailSizeToUse.Height);

        oGraphic.DrawImage(oImg,oRectangle);

        oThumbNail.Save(sPhysicalPath  + sThumbNailFileName,oFormat);

        oImg.Dispose();

    }
    catch (Exception ex)
    {
        Response.Write(ex.Message);
    }

}