Re: screen <-> printer

Author

Message

Sergey Tkachenko

Posted: 07/22/2003 19:15:33

Hi,

If you want to create the same image on printer and paper, you need:

1) Format reporthelper in printer resolution. You need to create

printer-compatible canvas and use it for reporthelper.Init()

Creating:

var

PrnCanvas: TCanvas;

PrnDC: HDC;

PrnCanvas := TCanvas.Create;

PrnDC := RV_GetPrinterDC; // from PtblRV unit

PrnCanvas.Handle := PrnDC;

PrnCanvas.Font.PixelsPerInch := GetDeviceCaps(PrnDC, LOGPIXELSY);

Destroying (when all drawing is finished)

PrnCanvas.Handle := 0;

DeleteDC(PrnDC);

PrnCanvas.Free;

2) When printing, use rvhelper.DrawPageAt(... Printer.Canvas ...), as I

guess you currently do

3) When drawing preview, you need to scale image.

There is a simple method for previewing: using TRVPrintPreview showing some

fake (empty) document. You can draw preview in OnPagePrepaint event.

Example: http://www.trichview.com/support/files/preview.zip

> Hi,

> I use TRVReportHelper to print multiple records of a report on one or more

> pages.

> TRVReportHelper draws the pages onto the printercanvas and as a preview to

> a TImage as in one of your demos. Of course it would be nice if the

preview

> would look like the print. But this is not the case.

> If I e.g. draw on the printercanvas in a given region of lets say 15 cm

the

> printer fits approx. 30 lines of text into this area. If I do the same

with

> the TImage it only fits 27-28 lines of text in the same region of 15 cm.

> This can leed to different number of pages send to the printer, and

created

> on the TImage as a preview. This can be pretty annoying.

> I calculate the width and height of my area in pixel with:

> function mmToPixel(mm:extended;dpi:integer):integer;

> begin

> Result := round( (mm / 25.4) * dpi );

> end;

> Where for the TImage dpi = GetDeviceCaps(TImage.Canvas.Handle, LOGPIXELSX)

> and for the printer dpi = GetDeviceCaps(printer.Handle, LOGPIXELSX).

> I assume it might have something to do with the difference in resolution

> ( 96 dpi <-> 600 dpi ) but I'm not sure.

> Furthermore in the TImage more characters can be fit in one line.

> To make it short: A page drawn to a printercanvas does not look like a

page

> drawn to an imagecanvas.

> Am I missing something or am I making something wrong?

> Perhaps you could enlighten me.

> Tia

> Frank Kroeger