我在谷歌上搜索某种解决方案，我找到了一个，我尝试在我的代码中实现它，但它不起作用。问题是，调整白色图像的大小后，它们会得到灰色边框。
这是我找到的解决方案的链接：
It says:出现此问题的原因是您将图像数据插值到
新尺寸，但沿边缘没有可插入的像素，.NET
默认情况下，这些边缘使用黑色像素。要解决这个问题，您需要使用
您的 DrawImage 调用中的 ImageAttributes 类......
代码 1：这是我使用 ImageAttributes 实现的代码：
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), 0, 0, 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：导致白色图像出现灰色边框的代码
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(), 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)
canvas.SmoothingMode = SmoothingMode.AntiAlias
canvas.InterpolationMode = InterpolationMode.HighQualityBicubic
canvas.PixelOffsetMode = PixelOffsetMode.HighQuality
canvas.DrawImage(oldImage, New Rectangle(New Point(0, 0), 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
2011 年 7 月 30 日更新：
代码1解决了白色图像上灰色边框的问题，但是有新问题。问题出在这行代码中：
canvas.DrawImage(oldImage, 新矩形(新点(0, 0), newSize), 0, 0, newImage.Width, newImage.Height, GraphicsUnit.Pixel, ia)
使用此代码，我得到具有所需宽度和高度且没有灰色边框的输出图像，但 oldImage 未缩放。
例如：
如果我想上传、调整大小并保存原始尺寸为 640x480px 且目标尺寸为 400px 的图像。作为输出，我得到一个宽度：400px，高度：300px，没有灰色边框的图像，但 oldImage 没有调整大小/缩放到 400px。这样，oldImage 就以原始分辨率绘制了。如何缩放oldImage才能正确绘制？有人可以指出我正确的解决方案或修改代码吗？
感谢大家，但我找到了解决所有问题的方法。
代码 1没有正常工作因为下面这行代码：
canvas.DrawImage(oldImage, 新矩形(新点(0, 0), newSize), 0, 0, newImage.Width, newImage.Height, GraphicsUnit.Pixel, ia)
解决方案：
canvas.DrawImage(oldImage, 新矩形(新点(0, 0), newSize), 0, 0,旧图像的宽度, 旧图像.高度, GraphicsUnit.Pixel, ia)
这是完整的工作代码（调整图像大小，没有灰色/黑色边框）：
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), 0, 0, oldImage.Width, oldImage.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
