Technical Information Database

TI1412D.txt - A Better Way To Print a Form

Category :Printing

Platform :All-32Bit

Product :All32Bit,

Description:

 The following TI details a better way to print the contents of a form, by getting the device independent bits in 256 colors

from the form, and using those bits to print the form to the printer. In addition, a check is made to see if the screen or printer

is a palette device, and if so, palette handling for the device is enabled. If the screen device is a palette device, an additional

step is taken to fill the bitmap's palette from the system palette, overcoming some buggy video drivers who don't fill the palette in.

Note: Since this code does a screen shot of the form, the form must be the topmost window and the whole from must be viewable when the

form shot is made.

unit Prntit;

interface

uses

SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics,

Controls, Forms, Dialogs, StdCtrls, ExtCtrls;

type

TForm1 = class(TForm)

Button1: TButton;

Image1: TImage;

procedure Button1Click(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

implementation

{$R *.DFM}

 uses Printers;

 procedure TForm1.Button1Click(Sender: TObject);

var

dc: HDC;

isDcPalDevice : BOOL;

MemDc :hdc;

MemBitmap : hBitmap;

OldMemBitmap : hBitmap;

hDibHeader : Thandle;

pDibHeader : pointer;

hBits : Thandle;

pBits : pointer;

ScaleX : Double;

ScaleY : Double;

ppal : PLOGPALETTE;

pal : hPalette;

Oldpal : hPalette;

i : integer;

begin

{Get the screen dc}

dc := GetDc(0);

{Create a compatible dc}

MemDc := CreateCompatibleDc(dc);

{create a bitmap}

MemBitmap := CreateCompatibleBitmap(Dc,

form1.width,

form1.height);

{select the bitmap into the dc}

OldMemBitmap := SelectObject(MemDc, MemBitmap);

{Lets prepare to try a fixup for broken video drivers}

isDcPalDevice := false;

if GetDeviceCaps(dc, RASTERCAPS) and

RC_PALETTE = RC_PALETTE then begin

GetMem(pPal, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)));

FillChar(pPal^, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)), #0);

pPal^.palVersion := $300;

pPal^.palNumEntries :=

GetSystemPaletteEntries(dc,

0,

256,

pPal^.palPalEntry);

if pPal^.PalNumEntries <> 0 then begin

pal := CreatePalette(pPal^);

oldPal := SelectPalette(MemDc, Pal, false);

isDcPalDevice := true

end else

FreeMem(pPal, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)));

end;

{copy from the screen to the memdc/bitmap}

BitBlt(MemDc,

0, 0,

form1.width, form1.height,

Dc,

form1.left, form1.top,

SrcCopy);

if isDcPalDevice = true then begin

SelectPalette(MemDc, OldPal, false);

DeleteObject(Pal);

end;

{unselect the bitmap}

SelectObject(MemDc, OldMemBitmap);

{delete the memory dc}

DeleteDc(MemDc);

{Allocate memory for a DIB structure}

hDibHeader := GlobalAlloc(GHND,

sizeof(TBITMAPINFO) +

(sizeof(TRGBQUAD) * 256));

{get a pointer to the alloced memory}

pDibHeader := GlobalLock(hDibHeader);

{fill in the dib structure with info on the way we want the DIB}

FillChar(pDibHeader^,

sizeof(TBITMAPINFO) + (sizeof(TRGBQUAD) * 256),

#0);

PBITMAPINFOHEADER(pDibHeader)^.biSize :=

sizeof(TBITMAPINFOHEADER);

PBITMAPINFOHEADER(pDibHeader)^.biPlanes := 1;

PBITMAPINFOHEADER(pDibHeader)^.biBitCount := 8;

PBITMAPINFOHEADER(pDibHeader)^.biWidth := form1.width;

PBITMAPINFOHEADER(pDibHeader)^.biHeight := form1.height;

PBITMAPINFOHEADER(pDibHeader)^.biCompression := BI_RGB;

{find out how much memory for the bits}

GetDIBits(dc,

MemBitmap,

0,

form1.height,

nil,

TBitmapInfo(pDibHeader^),

DIB_RGB_COLORS);

{Alloc memory for the bits}

hBits := GlobalAlloc(GHND,

PBitmapInfoHeader(pDibHeader)^.BiSizeImage);

{Get a pointer to the bits}

pBits := GlobalLock(hBits);

{Call fn again, but this time give us the bits!}

GetDIBits(dc,

MemBitmap,

0,

form1.height,

pBits,

PBitmapInfo(pDibHeader)^,

DIB_RGB_COLORS);

{Lets try a fixup for broken video drivers}

if isDcPalDevice = true then begin

for i := 0 to (pPal^.PalNumEntries - 1) do begin

PBitmapInfo(pDibHeader)^.bmiColors[i].rgbRed :=

pPal^.palPalEntry[i].peRed;

PBitmapInfo(pDibHeader)^.bmiColors[i].rgbGreen :=

pPal^.palPalEntry[i].peGreen;

PBitmapInfo(pDibHeader)^.bmiColors[i].rgbBlue :=

pPal^.palPalEntry[i].peBlue;

end;

FreeMem(pPal, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)));

end;

{Release the screen dc}

ReleaseDc(0, dc);

{Delete the bitmap}

DeleteObject(MemBitmap);

{Start print job}

Printer.BeginDoc;

{Scale print size}

if Printer.PageWidth < Printer.PageHeight then begin

ScaleX := Printer.PageWidth;

ScaleY := Form1.Height * (Printer.PageWidth / Form1.Width);

end else begin

ScaleX := Form1.Width * (Printer.PageHeight / Form1.Height);

ScaleY := Printer.PageHeight;

end;

{Just incase the printer drver is a palette device}

isDcPalDevice := false;

if GetDeviceCaps(Printer.Canvas.Handle, RASTERCAPS) and

RC_PALETTE = RC_PALETTE then begin

{Create palette from dib}

GetMem(pPal, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)));

FillChar(pPal^, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)), #0);

pPal^.palVersion := $300;

pPal^.palNumEntries := 256;

for i := 0 to (pPal^.PalNumEntries - 1) do begin

pPal^.palPalEntry[i].peRed :=

PBitmapInfo(pDibHeader)^.bmiColors[i].rgbRed;

pPal^.palPalEntry[i].peGreen :=

PBitmapInfo(pDibHeader)^.bmiColors[i].rgbGreen;

pPal^.palPalEntry[i].peBlue :=

PBitmapInfo(pDibHeader)^.bmiColors[i].rgbBlue;

end;

pal := CreatePalette(pPal^);

FreeMem(pPal, sizeof(TLOGPALETTE) +

(255 * sizeof(TPALETTEENTRY)));

oldPal := SelectPalette(Printer.Canvas.Handle, Pal, false);

isDcPalDevice := true

end;

{send the bits to the printer}

StretchDiBits(Printer.Canvas.Handle,

0, 0,

Round(scaleX), Round(scaleY),

0, 0,

Form1.Width, Form1.Height,

pBits,

PBitmapInfo(pDibHeader)^,

DIB_RGB_COLORS,

SRCCOPY);

{Just incase you printer drver is a palette device}

if isDcPalDevice = true then begin

SelectPalette(Printer.Canvas.Handle, oldPal, false);

DeleteObject(Pal);

end;

 {Clean up allocated memory}

GlobalUnlock(hBits);

GlobalFree(hBits);

GlobalUnlock(hDibHeader);

GlobalFree(hDibHeader);

 {End the print job}

Printer.EndDoc;

 end;

 Reference:

4/22/99 12:51:56 PM