Delphi 5 for Professionals/DELPHI5.iso/AddOns/Components/TEECHART/Delphi1_And_Delphi2/EXAMPLES/OTHER/Printing better/README.TXT

Text File | 1998-10-24 | 9.6 KB | 355 lines

Printing better.
----------------

This document explains how TeeChart components are
printed, and describes how to improve printing.

1- Introduction
2- Design issues
3- How to Print Proportionally?
4- Other problems
5- Printing Reference
6- More information


1- Introduction
----------------

The TeeChart library is sending Charts to the printer
using a Windows graphic format known as "metafile".

This format has several advantages and disadvantages
over using the bitmap format:

- It's much smaller, because graphic information is
stored in vector instructions, instead of pixels.
This results in a faster printing speed in most cases.
Also, the printer doesn't need to have more memory.

- Due to be a sequence of instructions instead of
a fixed array of pixels, a metafile can be resized
( or "stretched" ) without loosing resolution, and
with greater accuracy.

- New printers support metafile format natively, via
software driver or via "gdi hardware".

With Windows 32-bit (Windows 95 and Windows NT), an
extended metafile format is implemented. This is known
as "enhanced metafile".
Metafiles have the extension:  "*.wmf" and enhanced
metafiles:  "*.emf".


2- Design issues
-----------------

The main goal of using metafiles in TeeChart, is to
provide "wysiwyg" (what you see is what you get).
That is, printed charts should look as close as possible
to how they look at screen.

To do this, TeeChart creates a metafile of the Chart
image, and then sends this metafile to the printer.

At this point, the Windows GDI module and the
Windows Printer driver will take care of "painting" the
Chart image on paper.

This involves "stretching" or "resizing" the metafile,
from screen coordinates to printer logical pixels.

Example:
A Chart on screen is at rectangle:
 Left  : 100
 Top   : 100
 Right : 300
 Bottom: 400

And it gets printed at this paper rectangle:
 Left  : 400
 Top   : 1000
 Right : 1200
 Bottom: 1500

In this example, the Chart should be rescaled both
in width and height:

screen Width = 300 - 100 = 200
paper Width = 1200 - 400 = 800
relation screen / paper = 800 / 200 = 4  <---

screen Height = 400 - 100 = 300
paper Height = 1500 - 1000 = 500
relation screen / paper = 500 / 300 = 1.666...  <---


The problem is the relation between the horizontal
and vertical increments is not the same:

 4 <> 1.666...

This means the Chart will be expanded more in the
horizontal dimension than in the vertical dimension.

In this case, Windows increases font sizes and pen
widths using the new dimensions.

Note: Windows 16-bit ( 3.1, 3.11 ) do not resize
fonts as it does Windows 32-bit (95 and NT).
Text can overlap other Chart sections and look bad
positioned.
To fix this, see below "How to print proportionally?"

Windows 32-bit does a better job using the enhanced
metafile format, so text dimensions are calculated
precisely.


3- How to Print Proportionally?
-----------------------------

By default, the TChart components are printed
using margins that make the paper resulting chart
with the same proportions between width and height
than the screen chart.
This is controlled with the Chart1.PrintProportional
property.
The Print Preview dialog has a check-box to set
PrintProportional to True or False.

Some printers can show problems when printing
Charts *without* using proportional printer margins.
Specially in Windows 16-bit with Delphi 1.0
So, the PrintProportional property is recommended to
be True (the default).

One approach that allows you full control is to
create a metafile image ( TMetafile ) and then Draw the
Chart into it, and then send the image to the printer.
There is an example included.
This is the most low level printing operation you can do.

Another approach is to do the opposite.
To resize the Chart onscreen to match the desired proportion of
the printed paper chart:

  Chart1.Height:=Round(1.0*Printer.PageHeight*Chart1.Width/Printer.PageWidth);
  Chart1.Print;


4- Other problems
=====================

Increasing resolution:
----------------------

The metafile format is not aware of the "resolution"
concept.
This is means resolution information is not stored inside
the metafile image.

You can modify the Chart "resolution" *before* printing,
by setting this property:

Chart1.PrintResolution := -100 ;

Negative values (like -100 above), represent the porcentual
increment in resolution.
Zero means "wysiwyg".

More resolution is obtained by making all Chart fonts
smaller and thinner lines.
The metafile size is bigger when using more resolution.

Increasing resolution can improve inaccuracy in buggy
printer drivers calculations.


Printing non-solid lines:
-------------------------

In some printer / windows combinations, non-solid pen lines
such as "dot" or "dash" will be printed as solid.
This happens specially in some HP Laserjet printers.

It seems the only workaround is to set the Chart Pen Width
properties to Zero:

Chart1.LeftAxis.Grid.Width := 0;

Increasing resolution ( see above ) can make the printer
to show non-solid lines.

Colors:
---------

Many printers accept only a subset of the available Colors.
This means setting a Chart color to a non-supported
palette color may result in that color not being used by
the printer, thus not drawing anything.

In this situations, try with "well known" solid colors like
"clRed, clBlue, clYellow, clGreen".

Some printers include a "Color Mapping" configuration dialog.
(At Printer Properties dialog).


Printing directly:
------------------

Drawing a Chart directly onto a Printer GDI Handle or Canvas
is also possible.
The following code does it:

 Uses Printers;
 With Printer do
 begin
   BeginDoc;
   try
     Chart1.Draw( Canvas, Rect( 0,0,PageWidth,PageHeight ) );
   finally
     EndDoc;
   end;
 end;

You will see several problems printing directly:

-- The Chart background is gray color ( instead of white ).
-- Font sizes are extremely small.
-- There are many axis grid lines.
-- Lines are very thin.

One way to solve the above problems is using the metafile
printing mode, described in this document.

Another way (much more complicated) is to change all Font
sizes and pen Width properties.


Printer driver settings:
------------------------

Try to use always the latest "good" printer driver version.
Try changing the Windows Printer driver resolution settings,
and the spooler method (in Windows NT) to both "EMF" and
"RAW" modes.

"EMF" means all output is sent to the printer in metafile format.



5- Printing Reference
========================

See the help file for extended information and examples
on the following properties and methods.

The BASIC.PAS and UPRINT.PAS units in TeeDemo project
contain code showing custom printing.

The attached project shows Printing Margin adjustments
to avoid text overlaping in Delphi 1.0 on 16-bit Windows
systems.

Printing Properties:
---------------------

Properties involved in Chart printing are:

Chart1.PrintMargins
  The percentual space at the four sides of the paper page.

Chart1.PrintResolution
  The relation between screen dimensions and paper dimensions.

Chart1.PrintProportional
  True to set the paper margins to match screen proportions.

Printing methods:
-----------------

The TeeChart control has several methods designed for
printing:

Methods that print *and* eject the printed page:
=================================================

These are the default and more used TeeChart printing
methods.

Chart1.Print
  Uses default paper orientation and margins.

Chart1.PrintPortrait
  Sets paper in Portrait and uses default margins.

Chart1.PrintLandscape
  Sets paper in Landscape and uses default margins.

Chart1.PrintRect
  Uses default paper orientation and the Rect parameter to
  position the Chart on the page.


Methods that do not eject the printed page:
============================================

These methods allow printing more than one chart in the same
paper page, or print other things and Chart components on the
same page.

With these methods you need to call Printer.BeginDoc and EndDoc
yourself. See Delphi TPrinter documentation and the UPRINT.PAS
and BASIC.PAS units in TeeChart TEEDEMO project.

Chart1.PrintPartial
   Draws a Chart to the Printer Canvas at the passed rectangle.

Chart1.PrintPartialCanvas
   Draws a Chart to the passed Canvas at the passed rectangle.


Related methods and properties:
===============================

Not directly involved with printing, but useful for
advanced printing:

Chart1.Draw
   Draws a Chart to the passed Canvas, in screen "mode".
   "Screen mode" means with gray background and without
   using the metafile format.
   This method draws directly to the Canvas.

Chart1.TeeCreateMetafile
   Function that returns a metafile image of the Chart,
   with the passed Rect coordinates.

Chart1.Metafiling
   Boolean property indicating the Chart is now drawing
   onto a metafile image.

Chart1.Printing
   Boolean property indicating the Chart is now drawing
   onto a Printer Canvas.


6- More information:
====================

Information about printing and metafiles can be found
at Microsoft Windows 32-bit SDK help file, located at:

"..\Delphi 3(4)\(Borland Shared\Microsoft Help)Help\Win32.hlp"

Use the "Help Contents" (not the index) and scroll-down
up to the Metafiles chapter.

See also the Delphi's TMetafile and TMetafileCanvas objects
at Delphi's help file and GRAPHICS.PAS unit.

-------------------------------------------------------