Difference between revisions of "Developing with Graphics"
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− | The Lazarus code on this page has been taken from the $LazarusPath/examples/lazintfimage/fadein1.lpi project. So take a closer look at this example | + | The Lazarus code on this page has been taken from the $LazarusPath/examples/lazintfimage/fadein1.lpi project. So if you want a flying start with graphics programming take a closer look at this example. |
Revision as of 19:36, 31 March 2005
Overview
This page will be the start for tutorials with regard to manipulating Bitmaps and other graphics in your program. As I'm not a graphics programmer I invite all who are, to share their expertise! Just add a link to this page and create your own WiKi article. On this page some general information will be given.
Working with TBitmap
The first thing to remember is that Lazarus is meant to be platform independent, so any methods using Windows API functionality are out of the question. So a method like ScanLine is not supported by Lazarus because it is intended for Device Independant Bitmap and uses functions from the GDI32.dll. So this takes care of the FAQ: Why is there no ScanLine in Lazarus?
A fading example
Say you want to make a Fading picture. In Delphi you could do something like:
type
PRGBTripleArray = ^TRGBTripleArray;
TRGBTripleArray = array[0..32767] of TRGBTriple;
procedure TForm1.FadeIn(aBitMap: TBitMap);
var
Bitmap, BaseBitmap: TBitmap;
Row, BaseRow: PRGBTripleArray;
x, y, step: integer;
begin
Bitmap := TBitmap.Create;
try
Bitmap.PixelFormat := pf32bit; // or pf24bit
Bitmap.Assign(aBitMap);
BaseBitmap := TBitmap.Create;
try
BaseBitmap.PixelFormat := pf32bit;
BaseBitmap.Assign(Bitmap);
for step := 0 to 32 do begin
for y := 0 to (Bitmap.Height - 1) do begin
BaseRow := BaseBitmap.Scanline[y];
Row := Bitmap.Scanline[y];
for x := 0 to (Bitmap.Width - 1) do begin
Row[x].rgbtRed := (step * BaseRow[x].rgbtRed) shr 5;
Row[x].rgbtGreen := (step * BaseRow[x].rgbtGreen) shr 5; // Fading
Row[x].rgbtBlue := (step * BaseRow[x].rgbtBlue) shr 5;
end;
end;
Form1.Canvas.Draw(0, 0, Bitmap);
InvalidateRect(Form1.Handle, nil, False);
RedrawWindow(Form1.Handle, nil, 0, RDW_UPDATENOW);
end;
finally
BaseBitmap.Free;
end;
finally
Bitmap.Free;
end;
end;
This function in Lazarus could be implemented like:
procedure TForm1.FadeIn(ABitMap: TBitMap);
var
SrcIntfImg, TempIntfImg: TLazIntfImage;
ImgHandle,ImgMaskHandle: HBitmap;
FadeStep: Integer;
px, py: Integer;
CurColor: TFPColor;
TempBitmap: TBitmap;
begin
SrcIntfImg:=TLazIntfImage.Create(0,0);
SrcIntfImg.LoadFromBitmap(ABitmap.Handle,ABitmap.MaskHandle);
TempIntfImg:=TLazIntfImage.Create(0,0);
TempIntfImg.LoadFromBitmap(ABitmap.Handle,ABitmap.MaskHandle);
TempBitmap:=TBitmap.Create;
for FadeStep:=1 to 32 do begin
for py:=0 to SrcIntfImg.Height-1 do begin
for px:=0 to SrcIntfImg.Width-1 do begin
CurColor:=SrcIntfImg.Colors[px,py];
CurColor.Red:=(CurColor.Red*FadeStep) shr 5;
CurColor.Green:=(CurColor.Green*FadeStep) shr 5;
CurColor.Blue:=(CurColor.Blue*FadeStep) shr 5;
TempIntfImg.Colors[px,py]:=CurColor;
end;
end;
TempIntfImg.CreateBitmap(ImgHandle,ImgMaskHandle,false);
TempBitmap.Handle:=ImgHandle;
TempBitmap.MaskHandle:=ImgMaskHandle;
Canvas.Draw(0,0,TempBitmap);
end;
SrcIntfImg.Free;
TempIntfImg.Free;
TempBitmap.Free;
end;
The Lazarus code on this page has been taken from the $LazarusPath/examples/lazintfimage/fadein1.lpi project. So if you want a flying start with graphics programming take a closer look at this example.