I need to increase the CPU usage of my program in VB.net - vb.net

Question

I have a program that take an image and changes it to 1 bit B&W. It uses Lockbyte software to make it faster. BUT, when running it, it takes over a minute to process one image. When looking at the CPU usage it is only 5% at most once it is running. Is there a way to get the computer to use more CPU time? The indicator is showing that the computer is running below 50%, as low as 25%.
I just had one DUH thought, I forgot to add the resizing function into my program. It should help but I know I need to make the conversion faster yet. The program will be used to do 100 to 300 images per batch.
Most other programs I have seen do a conversion within a few seconds per image. I would like to get to something like this too.
This is the program. Mostly cobbled together from samples. I only half understand it but can read it. Sorry to the contributors that I cannot give credit to them. I didn't keep track of them.
Public Class Form1
Public Shared Function ConvertTo1Bit(ByVal input As Bitmap) As Bitmap
Dim masks = New Byte() {&H80, &H40, &H20, &H10, &H8, &H4, &H2, &H1}
Dim output = New Bitmap(input.Width, input.Height, PixelFormat.Format1bppIndexed)
Dim data = New SByte(input.Width - 1, input.Height - 1) {}
Dim inputData = input.LockBits(New Rectangle(0, 0, input.Width, input.Height), ImageLockMode.[ReadOnly], PixelFormat.Format24bppRgb)
Try
Dim scanLine = inputData.Scan0
Dim line = New Byte(inputData.Stride - 1) {}
Dim y = 0
While y < inputData.Height
Marshal.Copy(scanLine, line, 0, line.Length)
For x = 0 To input.Width - 1
data(x, y) = CSByte((64 * (GetGreyLevel(line(x * 3 + 2), line(x * 3 + 1), line(x * 3 + 0)) - 0.5)))
Next
y += 1
scanLine += inputData.Stride
End While
Finally
input.UnlockBits(inputData)
End Try
Dim outputData = output.LockBits(New Rectangle(0, 0, output.Width, output.Height), ImageLockMode.[WriteOnly], PixelFormat.Format1bppIndexed)
Try
Dim scanLine = outputData.Scan0
Dim y = 0
While y < outputData.Height
Dim line = New Byte(outputData.Stride - 1) {}
For x = 0 To input.Width - 1
Dim j = data(x, y) > 0
Try
If j Then
line(x / 8) = line(x / 8) Or masks(x Mod 8)
End If
Catch ex As Exception
End Try
Dim [error] = CSByte((data(x, y) - (If(j, 32, -32))))
If x < input.Width - 1 Then data(x + 1, y) += CSByte((7 * [error] / 16))
If y < input.Height - 1 Then
If x > 0 Then data(x - 1, y + 1) += CSByte((3 * [error] / 16))
data(x, y + 1) += CSByte((5 * [error] / 16))
If x < input.Width - 1 Then data(x + 1, y + 1) += CSByte((1 * [error] / 16))
End If
Next
Marshal.Copy(line, 0, scanLine, outputData.Stride)
y += 1
scanLine += outputData.Stride
End While
Finally
output.UnlockBits(outputData)
End Try
Return output
End Function
Public Shared Function GetGreyLevel(ByVal r As Byte, ByVal g As Byte, ByVal b As Byte) As Double
Return (r * 0.299 + g * 0.587 + b * 0.114) / 255
End Function
Private Sub btBrowesIn_Click(sender As Object, e As EventArgs) Handles btBrowesIn.Click
FolderBrowserDialog1.ShowDialog()
tbInPic.Text = FolderBrowserDialog1.SelectedPath
End Sub
Private Sub btBrowesOut_Click(sender As Object, e As EventArgs) Handles btBrowesOut.Click
FolderBrowserDialog2.ShowDialog()
tbInPic.Text = FolderBrowserDialog2.SelectedPath
End Sub
Private Sub btGo_Click(sender As Object, e As EventArgs) Handles btGo.Click
Dim Infiles As Array
Dim opf As New OpenFileDialog
opf.Filter = "Choose Image(*.jpg;*.png;*.gif)|*.jpg;*.png;*.gif"
If opf.ShowDialog = DialogResult.OK Then
PictureBox1.Image = Image.FromFile(opf.FileName)
Dim MyBitmap As New Bitmap(PictureBox1.Image)
PictureBox2.Image = ConvertTo1Bit(MyBitmap)
End If
End Sub
End Class

Answer 1

The program will be used to do 100 to 300 images per batch.
You can process the images asynchronously. .Net provides several ways to do this: Async/Await, raw Tasks, ThreadPool, raw Threads, BackgroundWorker, probably more. Which is most appropriate here depends on the context of the application.