VB.NET: Mengubah Ukuran Gambar (Resize Image)

Saat membangun sebuah aplikasi tidak jarang kita berurusan dengan penyimpanan gambar. Dan untuk menyimpan gambar secara efektif kadang kita perlu mengubah ukuran supaya lebih kecil. Nah kesempatan ini kita akan membuat contoh bagaimana sebuah file gambar diperkecil dengan menggunakan code VB.NET.

Proses pengubahan ukuran pada contoh kali ini, ukuran akan diubah dengan pilihan:
- Melalui Persentasi
- Melalui Width (lebar gambar) --> height otomatis menyesuaikan
- Melalui Height (tinggi gambar)--> width otomatis menyesuaikan

Mengapa Width dan Height tidak di set keduanya, supaya ratio gambar tetap terjaga, alias ga gepeng gituh...

UI:

Code:

Imports System.Drawing.Imaging

Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, _
                         ByVal e As System.EventArgs) Handles MyBase.Load

      PictureBox1.SizeMode = PictureBoxSizeMode.StretchImage
      PictureBox1.BorderStyle = BorderStyle.FixedSingle
      Label1.Text = "Image Source"
      Label2.Text = "Resize Type"
      Label3.Text = "Size to"
      Button1.Text = "Browse..."
      Button2.Text = "Resize"
      With ComboBox1
          .Items.Add("Percentage")
          .Items.Add("Width Scale")
          .Items.Add("Height Scale")
          .SelectedIndex = 0
      End With
      'default value of scale
      TextBox2.Text = 50

End Sub

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, _
          ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged

      If ComboBox1.SelectedIndex = 0 Then
          Label4.Text = "%"
      Else
          Label4.Text = "px"
      End If

End Sub

Public Sub ResizeImage(ByVal ImageSource As String, _
                        ByVal ResizeType As Integer, ByVal scale As Single, _
                        ByVal ResultPath As String)

      'source bitmap.
      Dim imgSource As New Bitmap(ImageSource)

      'resize type
      Select Case ResizeType
          Case 0 'percentage
              scale = scale / 100
          Case 1 'width px
              scale = scale / (imgSource.Width)
          Case 2 'height px
              scale = scale / (imgSource.Height)
      End Select

      'scale factor
      Dim sclFactor As Single = Single.Parse(scale)

      'bitmap for result
      Dim imgResult As New Bitmap( _
          CInt(imgSource.Width * sclFactor), _
          CInt(imgSource.Height * sclFactor))

      'Graphics object for result
      Dim grResult As Graphics = Graphics.FromImage(imgResult)

      'source to result bitmap
      grResult.DrawImage(imgSource, 0, 0, _
          imgResult.Width + 1, _
          imgResult.Height + 1)

      'save result
      imgResult.Save(ResultPath, ImageFormat.Jpeg)

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, _
              ByVal e As System.EventArgs) Handles Button1.Click

      With OpenFileDialog1
          .FileName = String.Empty
          .InitialDirectory = "C:\"
          .Title = "Open Image File"
          'filter image file
          .Filter = "Image Files |*.jpg;*.jpeg;*.png;*.bmp"
      End With
      Dim result As DialogResult = OpenFileDialog1.ShowDialog()
      If result = Windows.Forms.DialogResult.OK Then
          Try
              TextBox1.Text = OpenFileDialog1.FileName
              PictureBox1.ImageLocation = OpenFileDialog1.FileName
          Catch ex As Exception
              MsgBox("Error : " & ex.Message)
          End Try
      End If
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, _
              ByVal e As System.EventArgs) Handles Button2.Click

      SaveFileDialog1.Filter = "Image Files |*.jpg;*.jpeg;*.png;*.bmp"
      If SaveFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then

          ResizeImage(TextBox1.Text, ComboBox1.SelectedIndex, _
                      TextBox2.Text, SaveFileDialog1.FileName)

          MsgBox("Image resized.")

      End If

End Sub

End Class

Runtime:
Saat aplikasi pertama berjalan, tekan tombol Browse... untuk memilih file gambar.