I am trying to add a layer to an ImgView32, and on that layer I want to draw a line. But, I want that layer to be transparent, so it wont cover all the layers added previously. So I want to obtain:
layer 1 -> image
layer 2 -> another image
layer 3 -> draw a line
layer 4 -> another image
This is a following to question: Delphi Graphics32 how to draw a line with the mouse on a layer You will find the code that I use for drawing the line and declaring the BitmapLayer following the link. I do not want to add it here so the question will remain small.
Btw, I already tried to declare this for the drawing layer:
Bitmap.DrawMode := dmBlend;
BL.Bitmap.CombineMode:= cmMerge;
also this
Bitmap.DrawMode := dmTransparent;
BL.Bitmap.CombineMode:= cmMerge;
(BL -> The TBitmapLayer) No change. When I create the BitmapLayer, it sits ontop of the previous layers just like a white paper, hiding them. The question is: can this be done (making the layer transparent)? Then how?
Thank you
Here's a sample code, based on previous test. Maybe better post whole unit this time, including also the .dfm. The Memo and Button are just part of my usual test setup, not needed to demonstrate GR32.
First the .dfm:
object Form5: TForm5
Left = 0
Top = 0
Caption = 'Form6'
ClientHeight = 239
ClientWidth = 581
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnDestroy = FormDestroy
DesignSize = (
581
239)
PixelsPerInch = 96
TextHeight = 13
object ImgView: TImgView32
Left = 8
Top = 8
Width = 320
Height = 220
Bitmap.ResamplerClassName = 'TNearestResampler'
BitmapAlign = baCustom
Color = clLime
ParentColor = False
Scale = 1.000000000000000000
ScaleMode = smScale
ScrollBars.ShowHandleGrip = True
ScrollBars.Style = rbsDefault
ScrollBars.Size = 17
OverSize = 0
TabOrder = 0
end
object Button1: TButton
Left = 380
Top = 8
Width = 75
Height = 25
Caption = 'Button1'
TabOrder = 1
end
object Memo: TMemo
Left = 380
Top = 39
Width = 185
Height = 187
Anchors = [akLeft, akTop, akRight, akBottom]
ScrollBars = ssVertical
TabOrder = 2
WordWrap = False
ExplicitHeight = 218
end
end
And then the .pas:
unit Unit5;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, GR32, GR32_Image, GR32_Layers, GR32_Backends;
type
TForm5 = class(TForm)
ImgView: TImgView32;
Button1: TButton;
Memo: TMemo;
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
{ Private declarations }
FStartPoint, FEndPoint: TPoint;
FDrawingLine: boolean;
bm32: TBitmap32;
BL : TBitmapLayer;
FSelection: TPositionedLayer;
public
{ Public declarations }
procedure AddLineToLayer;
procedure SwapBuffers32;
procedure LayerMouseDown(Sender: TObject; Buttons: TMouseButton;Shift: TShiftState; X, Y: Integer);
procedure LayerMouseUp(Sender: TObject; Buttons: TMouseButton;Shift: TShiftState; X, Y: Integer);
procedure LayerMouseMove(Sender: TObject; Shift: TShiftState;X, Y: Integer);
procedure LayerOnPaint(Sender: TObject; Buffer: TBitmap32);
procedure SetSelection(Value: TPositionedLayer);
property Selection: TPositionedLayer read FSelection write SetSelection;
end;
var
Form5: TForm5;
implementation
{$R *.dfm}
var
imwidth: integer;
imheight: integer;
const
penwidth = 3;
pencolor = clBlue; // Needs to be a VCL color!
procedure TForm5.AddLineToLayer;
begin
bm32.Canvas.Pen.Color := pencolor;
bm32.Canvas.Pen.Width := penwidth;
bm32.Canvas.MoveTo(FStartPoint.X, FStartPoint.Y);
bm32.Canvas.LineTo(FEndPoint.X, FEndPoint.Y);
end;
procedure TForm5.FormCreate(Sender: TObject);
var
P: TPoint;
W, H: Single;
begin
imwidth := Form5.ImgView.Width;
imheight := Form5.ImgView.Height;
bm32 := TBitmap32.Create;
bm32.DrawMode := dmTransparent;
bm32.SetSize(imwidth,imheight);
bm32.Canvas.Pen.Width := penwidth;
bm32.Canvas.Pen.Color := pencolor;
with ImgView do
begin
Selection := nil;
Layers.Clear;
Scale := 1;
Scaled := True;
Bitmap.DrawMode := dmTransparent;
Bitmap.SetSize(imwidth, imheight);
Bitmap.Canvas.Pen.Width := penwidth;
Bitmap.Canvas.Pen.Color := clBlue;
Bitmap.Canvas.FrameRect(Rect(20, 20, imwidth-20, imheight-20));
Bitmap.Canvas.TextOut(15, 12, 'ImgView');
end;
BL := TBitmapLayer.Create(ImgView.Layers);
try
BL.Bitmap.DrawMode := dmTransparent;
BL.Bitmap.SetSize(imwidth,imheight);
BL.Bitmap.Canvas.Pen.Width := penwidth;
BL.Bitmap.Canvas.Pen.Color := pencolor;
BL.Location := GR32.FloatRect(0, 0, imwidth, imheight);
BL.Scaled := False;
BL.OnMouseDown := LayerMouseDown;
BL.OnMouseUp := LayerMouseUp;
BL.OnMouseMove := LayerMouseMove;
BL.OnPaint := LayerOnPaint;
except
BL.Free;
raise;
end;
FDrawingLine := false;
SwapBuffers32;
end;
procedure TForm5.FormDestroy(Sender: TObject);
begin
bm32.Free;
BL.Free;
end;
procedure TForm5.LayerMouseDown(Sender: TObject; Buttons: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
FStartPoint := Point(X, Y);
FDrawingLine := true;
// Memo.Lines.Add(Format('Start at x: %3d, y: %3d',[X, Y]))
end;
procedure TForm5.LayerMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
if FDrawingLine then
begin
SwapBuffers32;
BL.Bitmap.Canvas.Pen.Color := pencolor;
BL.Bitmap.Canvas.MoveTo(FStartPoint.X, FStartPoint.Y);
BL.Bitmap.Canvas.LineTo(X, Y);
// Memo.Lines.Add(Format('Draw at x: %3d, y: %3d',[X, Y]))
end;
end;
procedure TForm5.LayerMouseUp(Sender: TObject; Buttons: TMouseButton;
Shift: TShiftState; X, Y: Integer);
begin
if FDrawingLine then
begin
FDrawingLine := false;
FEndPoint := Point(X, Y);
AddLineToLayer;
SwapBuffers32;
// Memo.Lines.Add(Format('End at x: %3d, y: %3d',[X, Y]))
end;
end;
procedure TForm5.LayerOnPaint(Sender: TObject; Buffer: TBitmap32);
begin
SwapBuffers32;
end;
procedure TForm5.SetSelection(Value: TPositionedLayer);
begin
if Value <> FSelection then
begin
FSelection := Value;
end;
end;
procedure TForm5.SwapBuffers32;
begin
// BitBlt(B.Bitmap.Canvas.Handle, 0, 0, B.Bitmap.Width, B.Bitmap.Height, bm32.Canvas.Handle, 0, 0, SRCCOPY);
// B.Bitmap.Draw(0, 0, bm32);
// bm32.DrawTo(B.Bitmap);
// BL.Bitmap := bm32;
TransparentBlt(
BL.Bitmap.Canvas.Handle, 0, 0, BL.Bitmap.Width, BL.Bitmap.Height,
bm32.Canvas.Handle, 0, 0, bm32.Width, bm32.Height, clWhite);
end;
end.
As you see from the .dfm, I have set the background of ImgView to lime color. I also drew a rectangle and some text to show the transparency.
In SwapBuffers I tried TransparentBlt and seems to work. Outcommented is also direct assigning of bm32 to the layer bitmap, which also works, but may not always be what you want.