Scale Printing

Imports System.Drawing
Imports System.Reflection
Imports System.Drawing.Printing
Imports System.Windows.Forms
Imports System.Runtime.InteropServices
Imports System.IO

Public Class clsPrinting

    Private printDoc As PrintDocument
    Private printSettings As PrinterSettings
    Private imageFilename As String = ""

    Public Property Preview As Boolean = False
    Public Property Documentname As String = "Untitled document"
    Public Property Landscape As Boolean
        Get
            Return printSettings.DefaultPageSettings.Landscape
        End Get
        Set(value As Boolean)
            printSettings.DefaultPageSettings.Landscape = value
        End Set
    End Property
    Public Sub SetMinimumMargins()
        printSettings.DefaultPageSettings.Margins.Left = CInt(printSettings.DefaultPageSettings.HardMarginX) + 1
        printSettings.DefaultPageSettings.Margins.Top = CInt(printSettings.DefaultPageSettings.HardMarginY) + 1
        printSettings.DefaultPageSettings.Margins.Right = CInt(printSettings.DefaultPageSettings.HardMarginX) + 1
        printSettings.DefaultPageSettings.Margins.Bottom = CInt(printSettings.DefaultPageSettings.HardMarginY) + 1
    End Sub

    Public Sub New()
        MyBase.New()
        printSettings = New PrinterSettings
    End Sub

    Public Function ShowPrintDialog() As Boolean
        Try
            Dim pd As New PrintDialog
            pd.PrinterSettings = printSettings
            If pd.ShowDialog = Windows.Forms.DialogResult.OK Then
                printSettings = pd.PrinterSettings
                Return True
            Else
                Return False
            End If
        Catch ex As Exception
            VizualLib.clsErrorHandling.ThrowException(Me.ToString, MethodBase.GetCurrentMethod().Name, ex.Message)
            Return False
        End Try
    End Function

    ''' <summary>
    ''' Prints an image file to full screen on the selected printer
    ''' </summary>
    ''' <param name="imageFile"></param>
    ''' <remarks></remarks>
    Public Sub PrintImage(ByVal imageFile As String)
        Try
            printDoc = New PrintDocument
            AddHandler printDoc.PrintPage, AddressOf printDoc_PrintImage
            imageFilename = imageFile
            With printDoc
                .PrinterSettings = printSettings
                .DocumentName = _Documentname
                If _Preview Then
                    Dim prv As New PrintPreviewDialog
                    prv.Document = printDoc
                    prv.Width = Screen.PrimaryScreen.WorkingArea.Width
                    prv.Height = Screen.PrimaryScreen.WorkingArea.Height
                    prv.ShowDialog()
                Else
                    .Print()
                End If
            End With
        Catch ex As Exception
            VizualLib.clsErrorHandling.ThrowException(Me.ToString, MethodBase.GetCurrentMethod().Name, ex.Message)
        End Try
    End Sub

    Private Sub printDoc_PrintImage(ByVal sender As Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs)
        Try
            Dim DpiX As Single = 0, DpiY As Single = 0
            Dim bmp As Bitmap = CType(Bitmap.FromFile(imageFilename), Bitmap)
            Dim imgSizeRatio As Double = bmp.Width / bmp.Height
            Dim printBitmap As Bitmap

            With printSettings.DefaultPageSettings

                Dim pageWidth As Single = .Bounds.Width - .Margins.Left - .Margins.Right
                Dim pageHeight As Single = .Bounds.Height - .Margins.Top - .Margins.Bottom
                Dim pageSizeRatio As Double = 0

                GetImageDPI(imageFilename, DpiX, DpiY)

                pageSizeRatio = (pageWidth / pageHeight)

                If imgSizeRatio > pageSizeRatio Then
                    'scale to image width
                    printBitmap = ResizeImage(bmp, pageWidth / bmp.Width, DpiX, DpiY)
                Else
                    'scale to image height
                    printBitmap = ResizeImage(bmp, pageHeight / bmp.Height, DpiX, DpiY)
                End If
                printBitmap.Save("C:\scratch\outputfile.png", Imaging.ImageFormat.Png)
                e.Graphics.DrawImage(printBitmap, .Margins.Left, .Margins.Top)
            End With

            e.HasMorePages = False
        Catch ex As Exception
            VizualLib.clsErrorHandling.ThrowException(Me.ToString, MethodBase.GetCurrentMethod().Name, ex.Message)
        End Try
    End Sub

    ''' <summary>
    ''' Finds the Dots Per Inch of an Image File
    ''' </summary>
    ''' <param name="filename"></param>
    ''' <param name="dpiX"></param>
    ''' <param name="dpiY"></param>
    ''' <remarks>Returns 96DPI if an error occurs as this is the most common value</remarks>
    Private Sub GetImageDPI(ByVal filename As String, ByRef dpiX As Single, ByRef dpiY As Single)
        Try
            Dim workingImage As Image = Image.FromFile(imageFilename)
            Dim TempImg As Image = New Bitmap(workingImage.Width, workingImage.Height)
            Dim ImageDrawer As Graphics = Graphics.FromImage(TempImg)
            dpiX = ImageDrawer.DpiX
            dpiY = ImageDrawer.DpiY
        Catch ex As Exception
            dpiX = 96
            dpiY = 96
        End Try
    End Sub

    ''' <summary>
    ''' Resizes an image using the specified scaling factor whilst maintaining the images aspect ratio
    ''' </summary>
    ''' <param name="img"></param>
    ''' <param name="scaleFactor"></param>
    ''' <param name="dpiX"></param>
    ''' <param name="dpiY"></param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Private Function ResizeImage(ByRef img As Bitmap, ByVal scaleFactor As Double, ByVal dpiX As Single, ByVal dpiY As Single) As Bitmap
        Try
            Dim imgDest As New Bitmap(CInt(img.Width * scaleFactor * dpiX / 100), CInt(img.Height * scaleFactor * dpiY / 100))

            ' Make a Graphics object for the result Bitmap.
            Using grDest As Graphics = Graphics.FromImage(imgDest)
                ' Copy the source image into the destination bitmap.
                grDest.DrawImage(img, 0, 0, imgDest.Width, imgDest.Height)
            End Using

            Return imgDest
        Catch ex As Exception
            VizualLib.clsErrorHandling.ThrowException(Me.ToString, MethodBase.GetCurrentMethod().Name, ex.Message)
            Return Nothing
        End Try
    End Function

End Class