Building the Right Environment to Support AI, Machine Learning and Deep Learning
Here is a quick summary for those who just want the code and don't want to read the history. I have searched all over the Web for good printing code and was unable to find it. I have created a printing class that allows text to be formatted at the character level. It has taken me about a week to get what I have working correctly and I thought it would be nice to save others the time.
The Long Version
Now, for those who would like the longer version of the story. I was recently tasked with creating a Web application that would allow printing to be initiated without the irritation of having to respond to successive prompts. I chose ASP.NET for this project, not only because it is replacing traditional ASP but also because I had had experience with printing in prior versions of MS VB, which is one of the languages that ASP.NET supports. So, I started browsing the Internet, looking for a printing solution that would fit my needs; unfortunately, I didn't find one. Although I did find multiple solutions that allowed me to print a large block of text, I couldn't find anything that allowed me to control the formatting at the character level as I needed.
Through this process, I learned a lot. Here are some of the things I consider to be the most important or obscure. First, when using the OnPrintPage sub of the PrintDocument class, I had trouble understanding how multiple pages were printed because I couldn't find a sendpagetoprinter command. I learned that the PrintDocument class essentially puts the OnPrintPage sub into a while loop as long as e.HasMorePages=True; this means that as soon as your code is finished executing and the sub is done, the sub will start back over again if the HasMorePages value is true. There is no magical sustaining of where in the print job I am or what my variable values are, which means that I have to be sure that my variables scope is set correctly. The other big problem I had was figuring out the coordinates to start each character at considering they will be different if the char is bolded or not. This was resolved when one of the tutorials I looked up showed me how to use the MeasureString function from the Graphics object.
My final challenge came when I needed to make sure that words were not chopped off at the end of a line. To overcome this issue, I ended up putting a kind of memory in my program that allowed it to collect one word's worth of characters before printing them out. To make sure that this word still got printed, I implemented a rollback feature so the code would move to the next line or page and start printing at the position it was rolled back to.
My code is easily modified and shouldn't be too hard to understand. It is well commented. It recognizes the HTML bold tag and a special <ST=> tag that I created to take the place of what tables do in HTML. Paragraphs are separated using vbCrLf and lines will wrap correctly without chopping off a word.
Here is the block of code to instantiate and use the class:
' Create object, passing in text Dim MyPrintObject As New TextPrint("<B>this will be bold</B>" _ + vbCrLf + "<ST=400>this will start at 400 pixels", "MyPrinterName") ' Set font, defaults to times new roman, 12 if omitted MyPrintObject.Font = New Font("Tahoma", 8) ' Issue print command MyPrintObject.Print()
Here is the actual printing class that does the work:
Public Class TextPrint ' Inherits all the functionality of a PrintDocument Inherits Printing.PrintDocument ' Private variables to hold default font and text Private fntPrintFont As Font Private strText As String Dim MySplitLine As String() Dim varStart As Integer = 0 Dim varChar As Integer = 0 ' New constructor Public Sub New(ByVal Text As String, ByVal pName As String) ' Sets the file stream MyBase.New() varStart = 0 strText = Text MyBase.PrinterSettings.PrinterName = pName ' This is the key line for setting the printer MySplitLine = strText.Split(vbCrLf) End Sub Public Property Text() As String Get Return strText End Get Set(ByVal Value As String) strText = Value MySplitLine = strText.Split(vbCrLf) End Set End Property Protected Overrides Sub OnBeginPrint(ByVal ev _ As Printing.PrintEventArgs) ' Run base code MyBase.OnBeginPrint(ev) ' Sets the default font If fntPrintFont Is Nothing Then fntPrintFont = New Font("Times New Roman", 12, _ FontStyle.Regular, _ GraphicsUnit.Point) End If End Sub Public Property Font() As Font ' Allows the user to override the default font Get Return fntPrintFont End Get Set(ByVal Value As Font) fntPrintFont = Value End Set End Property Protected Overrides Sub OnPrintPage(ByVal e As _ Printing.PrintPageEventArgs) ' Provides the print logic for our document ' Run base code MyBase.OnPrintPage(e) ' Draw the margins (for debugging). 'e.Graphics.DrawRectangle(Pens.Red, e.MarginBounds) Dim the_font As Font = fntPrintFont Dim string_format As New StringFormat ' Draw the text left justified, ' wrap at words, and don't draw partial lines. string_format.Alignment = StringAlignment.Near string_format.FormatFlags = StringFormatFlags.LineLimit string_format.Trimming = StringTrimming.Word ' Draw some text. Dim ymin As Integer = e.MarginBounds.Top Dim layout_rect As RectangleF Dim text_size As SizeF Dim characters_fitted As Integer Dim lines_filled As Integer ' Prepare the fixed spacing for each character Dim fixedSpace As SizeF = e.Graphics.MeasureString("W", the_font) Static i As Integer For i = varStart To MySplitLine.GetUpperBound(0) ' get ready for the 1 char printing Dim smallArray As String(,) Dim xmin As Integer = e.MarginBounds.Left Dim varWord As RectangleF() ReDim varWord(1) Dim wordCountForLine As Integer = 0 ' make sure a space prints if a two vbcrlf's are in a row If Trim(Len(MySplitLine(i))) = 1 Then ReDim smallArray(3, 1) smallArray(0, 0) = "" smallArray(1, 0) = FontStyle.Regular smallArray(2, 0) = -1 ymin += CInt(the_font.Height) Else ' Special print 1 char at a time for formatting smallArray = checkBold(Trim(MySplitLine(i).ToString), _ fntPrintFont) 'END print 1 char at a time for formatting End If Dim x As Integer For x = varChar To smallArray.GetUpperBound(1) - 1 'remove blanks so ascii works If smallArray(0, x).Length = 0 _ Then smallArray(0, x) = Chr(0) ' Get the font for measurement. the_font = New Font(fntPrintFont.Name, _ fntPrintFont.Size, _ CInt(smallArray(1, x)), fntPrintFont.Unit) ' Set the text start location if desired If CInt(smallArray(2, x)) > -1 Then xmin = _ CInt(smallArray(2, x)) ' Get the area available for this text. layout_rect = New RectangleF(xmin, ymin, _ e.MarginBounds.Right - xmin, the_font.Height) ' If the layout rectangle's height < 1, make it 1. If layout_rect.Height < 1 Then layout_rect.Height = 1 ' See how big the text will be and ' how many characters will fit. text_size = e.Graphics.MeasureString(smallArray(0, _ x).ToString, the_font, _ New SizeF(layout_rect.Width, layout_rect.Height), _ string_format, characters_fitted, lines_filled) ' See if any characters will fit. If characters_fitted > 0 Then ' start accumulating the print location varWord(varWord.GetUpperBound(0) - 1) = layout_rect ' *********Draw the word when finished.********* If Asc(smallArray(0, x).Chars(0)) = 32 _ Or x = smallArray.GetUpperBound(1) - 1 Then Dim z As Integer For z = x - (varWord.GetUpperBound(0) - 1) To x ' Get the font for measurement. the_font = New Font(fntPrintFont.Name, _ fntPrintFont.Size, CInt(smallArray(1, z)), _ fntPrintFont.Unit) ' actually print the character on the page. e.Graphics.DrawString(smallArray(0, z), _ the_font, Brushes.Black, _ varWord((z - x) + _ (varWord.GetUpperBound(0) - _ 1)), string_format) Next xmin += 4 ReDim varWord(0) wordCountForLine += 1 End If '' Draw a rectangle around the text (for debugging). 'e.Graphics.DrawRectangle(Pens.Green, _ ' layout_rect.Left, _ ' layout_rect.Top, _ ' text_size.Width, _ ' text_size.Height) ' Increase the location where we can start. xmin += CInt(text_size.Width) - _ (fixedSpace.Width * 0.25) ReDim Preserve varWord(varWord.GetUpperBound(0) + 1) ElseIf Asc(smallArray(0, x).Chars(0)) < 30 Then ' make sure to dispose of odd char's in the array Else ' See if some of the paragraph didn't fit ' ****Draw the word if longer than one line.****** If wordCountForLine = 0 Then varWord(varWord.GetUpperBound(0) - 1) = layout_rect Dim z As Integer For z = x - (varWord.GetUpperBound(0) - 1) To x e.Graphics.DrawString(smallArray(0, z), _ the_font, Brushes.Black, _ varWord((z - x) + (varWord.GetUpperBound(0) - _ 1)), string_format) Next ReDim varWord(0) End If '*******reset the variables********* wordCountForLine = 0 x -= varWord.GetUpperBound(0) ReDim varWord(1) xmin = e.MarginBounds.Left ymin += CInt(the_font.Height) ' move to the next line 'see if there are more lines available If (e.MarginBounds.Bottom - ymin) < the_font.Height Then Exit For ' exit for loop so page can print End If End If Next ymin += CInt(the_font.Height) ' move to the next line If (e.MarginBounds.Bottom - ymin) < the_font.Height Then varChar = x 'save character location varStart = i 'save line location e.HasMorePages = True 'after printing page, run sub again Exit For ' exit for loop so page can print Else varChar = 0 e.HasMorePages = False End If Next End Sub Private Function checkBold(ByVal varString As String, _ ByVal startFont As Font) As String(,) Dim aryString As String(,) ReDim aryString(3, 1) Dim printStyle As FontStyle = FontStyle.Regular Dim varStartPlace As Integer = -1 aryString(0, 0) = "" 'initialize the array to avoid errors aryString(1, 0) = printStyle aryString(2, 0) = varStartPlace Dim varPlace As Integer = 0 For varPlace = 1 To varString.Length If Mid(varString, varPlace, 3) = "<B>" Then printStyle = FontStyle.Bold varPlace += 2 ElseIf Mid(varString, varPlace, 4) = "</B>" Then printStyle = FontStyle.Regular varPlace += 3 ElseIf Mid(varString, varPlace, 4) = "<ST=" Then varStartPlace = CInt(Mid(varString, varPlace + 4, _ InStr(varPlace + 4, varString, ">") - (varPlace + 4))) varPlace += 4 + varStartPlace.ToString.Length Else ReDim Preserve aryString(3, aryString.GetUpperBound(1) + 1) aryString(0, aryString.GetUpperBound(1) - 1) = _ Mid(varString, varPlace, 1) aryString(1, aryString.GetUpperBound(1) - 1) = printStyle aryString(2, aryString.GetUpperBound(1) - 1) = _ varStartPlace varStartPlace = -1 End If Next checkBold = aryString End Function End Class
Obviously, there are many enhancements that can be done to it; however, it should be a great start for most programmers.
If you have comments or questions, I monitor this thread: Printing in .NET.