Detecting resolution for Printer object

[cjreynolds]

I'm using the Printer object (VB6) to print graphics and need to detect the printer's resolution (in DPI). Tried

X = Printer.PrintQu aliy

to no avail. Returns a zero.

It's been several years since I worked with VB, I guess I'm easily stumped...

Can it be calculated using TwipsPerPixel?

Thanks,

joe

[Killer42]

I'm using the Printer object (VB6) to print graphics and need to detect the printer's resolution (in DPI). Tried
X = Printer.PrintQu aliy
to no avail. Returns a zero.
It's been several years since I worked with VB, I guess I'm easily stumped...
Can it be calculated using TwipsPerPixel?

Yes, twips per pixel seems as though it should (indirectly) give you what you want. A twip is 1/1440th of an inch. Or (if you live somewhere that has moved on from the Dark Ages) about 0.017639 of a millimetre.

[cjreynolds]

I think I've found a better way using GetDeviceCaps() :

Private Declare Function GetDeviceCaps Lib "gdi32" _
(ByVal hdc As Long, ByVal nIndex As Long) As Long
      
Private Const LOGPIXELSX = 88
Private Const LOGPIXELSY = 90

Private Sub Command1_Click()
Dim dpiX As Long, dpiY As Long
    dpiX = GetDeviceCaps(Printer.hdc, LOGPIXELSX)
    dpiY = GetDeviceCaps(Printer.hdc, LOGPIXELSY)

    MsgBox (dpiX & " " & dpiY)
End Sub

I think this is working - if you can confirm/deny it's validity, please tell me.

Now that I (hopefully) have the printer resolution, how do I use that to put something on paper at, say, X = 2 inches, Y = 4 inches? I've been using this code to scale/position the image:

Sub SetLargePrinterScale(obj As Object, VertPosition As Single)
Dim Owid As Single
Dim Ohgt As Single
Dim Pwid As Single
Dim Phgt As Single
Dim Xmid As Single
Dim Ymid As Single
Dim S As Single
Dim ScaleFactor As Single

    ScaleFactor = (50 - frmPrint.Slider3.Value) / 10
    
    Owid = obj.ScaleX(obj.ScaleWidth, obj.ScaleMode, vbPixels)
    Ohgt = obj.ScaleY(obj.ScaleHeight, obj.ScaleMode, vbPixels)
    
    Pwid = Printer.ScaleX(Printer.ScaleWidth, Printer.ScaleMode, vbPixels)
    Phgt = Printer.ScaleY(Printer.ScaleHeight, Printer.ScaleMode, vbPixels)
    
    If Ohgt / Owid > Phgt / Pwid Then
        S = Phgt / Ohgt
    Else
        S = Pwid / Owid
    End If
    
    Pwid = obj.ScaleX(Pwid * ScaleFactor, vbPixels, obj.ScaleMode) / S
    Phgt = obj.ScaleY(Phgt * ScaleFactor, vbPixels, obj.ScaleMode) / S
    
    Xmid = (obj.ScaleLeft + obj.ScaleWidth / 2) * ScaleFactor
    Ymid = (obj.ScaleTop + obj.ScaleHeight / 1.6) * ScaleFactor
    
    
    Printer.Scale (Xmid - Pwid / 2, Ymid - Phgt / 2)-(Xmid + Pwid / 2, Ymid + Phgt / 2)

End Sub

It prints the output in the middle of the page (X and Y). To move the printout away from the center, I've been adding an integer to the Xmid and Ymid equations:

Xmid = (obj.ScaleLeft + obj.ScaleWidth / 2) * ScaleFactor + 100
Ymid = (obj.ScaleTop + obj.ScaleHeight / 1.6) * ScaleFactor + 200

but for portability I need to take the current printer resolution into account.

Any suggestions?

joe

[Killer42]

I haven't looked into this in detail yet (and it's not an area I'm really familiar with anyway). But I do know that you can produce the same results two ways...

dpiX = GetDeviceCaps(Printer.hdc, LOGPIXELSX)
dpiY = GetDeviceCaps(Printer.hdc, LOGPIXELSY)

dpiX = 1440 / Printer.TwipsPerPixelX
dpiY = 1440 / Printer.TwipsPerPixelY

Not a lot of difference really, except that the TwipsPerPixelX/Y are already available without any declarations. I guess it's just a matter of which way you prefer to go.

[cjreynolds]

That works - Thanks!