Как изменить палитру TBitmap

← →
bug008 (2004-08-27 16:12) [0]

Здравствуйте.
Если у битмапа установить свойства:
Bitmap.HandleType := bmDIB;
Bitmap.PixelFormat := pf8bit;
То при отображениии картинки будет использоваться палитра, которая поумолчанию содержит 16 системных цветов, все остальные элементры палитры черный цвет.
Как поменять палитру так, чтобы были только цвета градации серого (0 - черный, 255 - белый)?
Спасибо.

← →
Анонимщик © (2004-08-27 16:39) [1]

В справке написано:

Objects

The example demonstrates using the TBitmap object.

Running

To run this example, load the project file from the Help\Examples\Bitmap directory.

Description

This example demonstrates changing the palette of a TBitmap object. A TBitmap is an encapsulation of the windows BITMAP and PALETTE which manages realizing of the palette automatically. The bitmap can be loaded from a .BMP file (LoadFromFile method) or a resource (LoadFromResourceName or LoadFromResourceID method) and saved back to a file (SaveToFile method). It can be drawn on a canvas by using the TCanvas" Draw or StretchDraw method. The size of the bitmap can be determined by using the Height and Width properties of TBitmap.

The example below illustrates the use of TBitmap’s Palette, LoadFromFile, Draw, Height, and Width. Be sure that a small bitmap file named bor6.bmp is present in the same directory as the .exe file.

Disclaimer

VCL Reference
TBitmap example (bmpformu.pas)

bmpformu.dfm:

object BmpForm: TBmpForm

Left = 311
Top = 321
Width = 466
Height = 334
Caption = "BmpForm"
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = "MS Sans Serif"
Font.Style = []
OnCreate = FormCreate
OnDestroy = FormDestroy
OnPaint = FormPaint
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
Left = 56
Top = 40
Width = 113
Height = 25
Caption = "Scramble Palette"
TabOrder = 0

OnClick = Button1Click
end
end

This is an example of using TBitmaps and is not intended to be an efficient method of tiling a form.

unit bmpformu;

//
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls;
type
TBmpForm = class(TForm)
Button1: TButton;
procedure FormDestroy(Sender: TObject);
procedure FormPaint(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
Bitmap: TBitmap;
procedure ScrambleBitmap;

procedure WMEraseBkgnd(var m: TWMEraseBkgnd); message WM_ERASEBKGND;
public
{ Public declarations }
end;
var
BmpForm: TBmpForm;
implementation

{$R *.DFM}

procedure TBmpForm.FormCreate(Sender: TObject);
begin
Bitmap := TBitmap.Create;
Bitmap.LoadFromFile("bor6.bmp");
end;
procedure TBmpForm.FormDestroy(Sender: TObject);
begin
Bitmap.Free;
end;
// since we"re going to be painting the whole form, handling this

// message will suppress the uneccessary repainting of the background
// which can result in flicker.
procedure TBmpform.WMEraseBkgnd(var m : TWMEraseBkgnd);
begin
m.Result := LRESULT(False);
end;
procedure TBmpForm.FormPaint(Sender: TObject);
var
x, y: Integer;
begin
y := 0;
while y < Height do
begin
x := 0;
while x < Width do
begin
Canvas.Draw(x, y, Bitmap);

x := x + Bitmap.Width;
end;
y := y + Bitmap.Height;
end;
end;
procedure TBmpForm.Button1Click(Sender: TObject);
begin
ScrambleBitmap;
Invalidate;
end;

//
// scrambling the bitmap is easy when it has 256 colors:
// we just need to change each of the colors in the palette
// to some other value.
//
procedure TBmpForm.ScrambleBitmap;
var
pal: PLogPalette;
hpal: HPALETTE;

i: Integer;
begin
pal := nil;
try
GetMem(pal, sizeof(TLogPalette) + sizeof(TPaletteEntry) * 255);
pal.palVersion := $300;
pal.palNumEntries := 256;
for i := 0 to 255 do
begin
pal.palPalEntry[i].peRed := Random(255);
pal.palPalEntry[i].peGreen := Random(255);
pal.palPalEntry[i].peBlue := Random(255);
end;
hpal := CreatePalette(pal^);
if hpal <> 0 then

Bitmap.Palette := hpal;
finally
FreeMem(pal);
end;
end;
end.

И еще:

TBitmap.PixelFormat

Indicates the bit format of the bitmap image, specifying how the image is displayed and how the pixels of the bitmap image are stored in memory.

type TPixelFormat = (pfDevice, pf1bit, pf4bit, pf8bit, pf15bit, pf16bit, pf24bit, pf32bit, pfCustom);
property PixelFormat: TPixelFormat;

Description

Use PixelFormat to change a TBitmap"s internal image to a particular memory format and color depth, or to find out what memory format and color depth a TBitmap is using.

For example, PixelFormat can be used to set the pixel format of the bitmap image to 8-bit for video drivers that cannot display the native format of a bitmap image.

Note: The PixelFormat of a JPEG image object applies to the bitmap if the JPEG image is copied to it.

Changing the pixel format is most commonly used with ScanLine, because your code must decode the pixel data accessed by ScanLine. Image-editing tools usually use one pixel for all internal image operations and copy the results to the screen (in whatever format) as the last step.

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