How to crop an image in vb.net?

问题:

The image can be anything. It can be jpg, png, anything.

Load it.

Crop it. Say removing first 100 pixels from the left.

Save to the same file

回答1:

Use Graphics.DrawImage Method (Image, RectangleF, RectangleF, GraphicsUnit) method.

    Dim fileName = "C:\file.jpg"
    Dim CropRect As New Rectangle(100, 0, 100, 100)
    Dim OriginalImage = Image.FromFile(fileName)
    Dim CropImage = New Bitmap(CropRect.Width, CropRect.Height)
    Using grp = Graphics.FromImage(CropImage)
        grp.DrawImage(OriginalImage, New Rectangle(0, 0, CropRect.Width, CropRect.Height), CropRect, GraphicsUnit.Pixel)
        OriginalImage.Dispose()
        CropImage.Save(fileName)
    End Using

回答2:

Ref: Graphics.DrawImage and Image Cropping with Image Resizing Using VB.NET

private void btnCropImage_Click(object sender, EventArgs e)
    {
        OpenFileDialog dlg = new OpenFileDialog();
        dlg.ShowDialog();
        //check your filename or set constraint on fileopen dialog
        //to open image files
        string str = dlg.FileName;

        //Load Image File to Image Class Object to make crop operation
        Image img = System.Drawing.Bitmap.FromFile(str);

        // Create rectangle for source image, what ever it's size. 
        GraphicsUnit units = GraphicsUnit.Pixel;
        RectangleF srcRect = img.GetBounds(ref units);

        // Create rectangle for displaying image - leaving 100 pixels from left saving image size.
        RectangleF destRect = new RectangleF(100.0F, 0.0F, srcRect.Width - 100, srcRect.Height);

        // Bitmap class object to which saves croped image
        Bitmap bmp = new Bitmap((int)srcRect.Width - 100, (int)srcRect.Height);

        // Draw image to screen.
        Graphics grp = Graphics.FromImage(bmp);
        grp.DrawImage(img, destRect, srcRect, units);

        //save image to disk
        bmp.Save("e:\\img.jpeg", System.Drawing.Imaging.ImageFormat.Jpeg);

        //Clear memory for Unused Source Image
        img.Dispose();
    }

Hope this help you..

回答3:

Region "Image Cropping"

Dim cropX As Integer
Dim cropY As Integer
Dim cropWidth As Integer
Dim cropHeight As Integer

Dim oCropX As Integer
Dim oCropY As Integer
Dim cropBitmap As Bitmap

Public cropPen As Pen
Public cropPenSize As Integer = 1 '2
Public cropDashStyle As Drawing2D.DashStyle = Drawing2D.DashStyle.Solid
Public cropPenColor As Color = Color.Yellow
Private Sub RotateBtn_Click(sender As System.Object, e As EventArgs) Handles RotateBtn.Click

    ' RotateImage(PreviewPictureBox.Image, offset:=, angle:=90)
    crobPictureBox.Image.RotateFlip(RotateFlipType.Rotate270FlipNone)
    'PreviewPictureBox.Image.RotateFlip(RotateFlipType.Rotate270FlipNone)
    '(45, PreviewPictureBox.Image)
End Sub
Private Sub crobPictureBox_MouseDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles crobPictureBox.MouseDown
    Try

        If e.Button = Windows.Forms.MouseButtons.Left Then

            cropX = e.X
            cropY = e.Y

            cropPen = New Pen(cropPenColor, cropPenSize)
            cropPen.DashStyle = DashStyle.DashDotDot
            Cursor = Cursors.Cross

        End If
        crobPictureBox.Refresh()
    Catch exc As Exception
    End Try
End Sub
Dim tmppoint As Point
Private Sub crobPictureBox_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles crobPictureBox.MouseMove
    Try

        If crobPictureBox.Image Is Nothing Then Exit Sub

        If e.Button = Windows.Forms.MouseButtons.Left Then

            crobPictureBox.Refresh()
            cropWidth = e.X - cropX
            cropHeight = e.Y - cropY
            crobPictureBox.CreateGraphics.DrawRectangle(cropPen, cropX, cropY, cropWidth, cropHeight)
        End If
        ' GC.Collect()

    Catch exc As Exception

        If Err.Number = 5 Then Exit Sub
    End Try

End Sub

Private Sub crobPictureBox_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles crobPictureBox.MouseUp
    Try
        Cursor = Cursors.Default
        Try

            If cropWidth < 1 Then
                Exit Sub
            End If

            Dim rect As Rectangle = New Rectangle(cropX, cropY, cropWidth, cropHeight)
            Dim bit As Bitmap = New Bitmap(crobPictureBox.Image, crobPictureBox.Width, crobPictureBox.Height)

            cropBitmap = New Bitmap(cropWidth, cropHeight)
            Dim g As Graphics = Graphics.FromImage(cropBitmap)
            g.InterpolationMode = Drawing2D.InterpolationMode.HighQualityBicubic
            g.PixelOffsetMode = Drawing2D.PixelOffsetMode.HighQuality
            g.CompositingQuality = Drawing2D.CompositingQuality.HighQuality
            g.DrawImage(bit, 0, 0, rect, GraphicsUnit.Pixel)
            ' g.DrawImage(bit, 0, 0, rect,GraphicsUnit.Pixel)
            PreviewPictureBox.Image = cropBitmap

        Catch exc As Exception
        End Try
    Catch exc As Exception
    End Try
End Sub