ASP.NET裁剪图像不进行裁剪

Question

我想将图像调整到最大宽度和高度，然后裁剪它。调整大小有效。但我在这里找到的裁剪代码没有。

我自己现有的代码使用字节数组，所以我需要使用它。

因此，下面的代码会调整大小，不会裁剪，并保存新图像。我的裁剪做错了什么？

Dim imgNewWidth, imgNewHeight As Integer
Dim _originalThumbWidth As Integer = 900
Dim _originalThumbHeight As Integer = 900
Dim imageURL As String = "https://med.stanford.edu/news/all-news/2021/09/cat-fur-color-patterns/_jcr_content/main/image.img.780.high.jpg/cat_by-Kateryna-T-Unsplash.jpg"
Dim localImagePath As String = Server.MapPath("images_tmp") + "CROPPED.jpg"
ResizeAndSaveFast(_originalThumbWidth, _originalThumbHeight, imageURL, localImagePath, "", "", imgNewWidth, imgNewHeight)

Private Function ResizeAndSaveFast(ByVal maxWidth As Integer, ByVal maxHeight As Integer, ByVal imageURL As String, ByVal saveToPath As String, ByVal userName As String, ByVal password As String,
ByRef imgNewWidth As Integer, ByRef imgNewHeight As Integer) As Boolean
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
Dim imgRequest As WebRequest = WebRequest.Create(imageURL)
Dim imgResponse As WebResponse
Dim memStream As New MemoryStream
Try
imgResponse = imgRequest.GetResponse()
Dim streamPhoto As Stream = imgResponse.GetResponseStream()
streamPhoto.CopyTo(memStream)
memStream.Position = 0
Catch ex As Exception
Return False
End Try

Dim bfPhoto As BitmapFrame = ReadBitmapFrame(memStream)
Dim newWidth, newHeight As Integer
Dim scaleFactor As Double
newWidth = bfPhoto.PixelWidth
newHeight = bfPhoto.PixelHeight
imgNewWidth = newWidth
imgNewHeight = newHeight
If bfPhoto.PixelWidth > maxWidth Or bfPhoto.PixelHeight > maxHeight Then
If bfPhoto.PixelWidth > maxWidth Then
scaleFactor = maxWidth / bfPhoto.PixelWidth
newWidth = CInt(Math.Round(bfPhoto.PixelWidth * scaleFactor, 0))
newHeight = CInt(Math.Round(bfPhoto.PixelHeight * scaleFactor, 0))
End If
If newHeight > maxHeight Then
scaleFactor = maxHeight / newHeight
newWidth = CInt(Math.Round(newWidth * scaleFactor, 0))
newHeight = CInt(Math.Round(newHeight * scaleFactor, 0))
End If
End If
imgNewWidth = newWidth
imgNewHeight = newHeight
Dim bfResize As BitmapFrame = FastResize(bfPhoto, newWidth, newHeight)
Dim baResize As Byte() = ToByteArray(bfResize)
Dim bmp As System.Drawing.Bitmap = imageFunctions.ConvertByteArrayToBitmap(baResize)
Dim CropArea As Rectangle = New Rectangle(100, 100, bmp.Width - 100, bmp.Height - 100)
Dim bm As Bitmap = New Bitmap(CropArea.Width, CropArea.Height)

Using g As Graphics = Graphics.FromImage(bm)
g.DrawImage(bm, New Rectangle(0, 0, bm.Width, bm.Height),
CropArea,
GraphicsUnit.Pixel)
End Using

bm.Save(saveToPath, ImageFormat.Jpeg)
Return True

End Function

Answer 1

由于使用了过于相似的变量名，导致了拼写错误。正如所写的，你有这个代码块：

Dim bmp As System.Drawing.Bitmap = imageFunctions.ConvertByteArrayToBitmap(baResize)
Dim CropArea As Rectangle = New Rectangle(100, 100, bmp.Width - 100, bmp.Height - 100)
Dim bm As Bitmap = New Bitmap(CropArea.Width, CropArea.Height)

Using g As Graphics = Graphics.FromImage(bm)
g.DrawImage(bm, New Rectangle(0, 0, bm.Width, bm.Height),
CropArea,
GraphicsUnit.Pixel)
End Using

此行：

g.DrawImage(bm, 
New Rectangle(0, 0, bm.Width, bm.Height),
CropArea,
GraphicsUnit.Pixel)

应为：

g.DrawImage(bmp, 
New Rectangle(0, 0, bm.Width, bm.Height),
CropArea,
GraphicsUnit.Pixel)

在代码中，您创建了变量bmp来存储未裁剪的位图。换句话说，就是您的源数据。

然后声明bm以存储裁剪后的位图，即您的目的地。图形对象g是使用目的地创建的。

在对g.DrawImage的调用中，第一个参数应该是源数据bmp。相反，你有目的地bm。

Answer 2

我还没有测试，但我认为您应该在这行代码中使用不同的变量。

g.DrawImage(bmp, New Rectangle(0, 0, bm.Width, bm.Height),
CropArea,
GraphicsUnit.Pixel)