Delphi Graphics32 相对鼠标位置（到图层）

Question

我有一个 ImgView32，它固定在所有表单边距上。表格已最大化。

ImgView的位图不固定（可以有不同的大小）

我正在尝试使用来自这个问题的代码在透明层上画一条线：

现在的问题是，使用那个确切的代码，我只能在左上角绘制，如下图所示：

如您所见，只能在左上角绘制线条。如果我尝试为起点和终点添加一些值，整个事情就会变得疯狂。所以我必须找到一种方法来翻译点，这样用户就只能在中心矩形的内部绘制（在图像中可见）

我没主意了。

请帮忙

这是整个单元：

unit MainU;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,GR32, GR32_Image, GR32_Layers, GR32_Backends, GR32_PNG, StdCtrls,
  ExtCtrls;

type
  TForm5 = class(TForm)
    ImgView: TImgView32;
    Button1: TButton;
    Memo: TMemo;
    Edit3: TEdit;
    Button2: TButton;
    RadioGroup1: TRadioGroup;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure ImgViewPaintStage(Sender: TObject; Buffer: TBitmap32;
      StageNum: Cardinal);
    procedure ImgViewResize(Sender: TObject);
 private
    { Private declarations }
    FStartPoint, FEndPoint: TPoint;
    FDrawingLine: boolean;
    bm32: TBitmap32;
    BL : TBitmapLayer;
    FSelection: TPositionedLayer;
 public
    { Public declarations }
    procedure AddLineToLayer;
    procedure AddCircleToLayer;
    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;

    Procedure SelectGraficLayer(idu:string);
    procedure AddTransparentPNGlayer;

  end;

var
  Form5: TForm5;

implementation

{$R *.dfm}

var
  imwidth: integer;
  imheight: integer;
  OffsX, OffsY: 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;

  with ImgView.PaintStages[0]^ do
  begin
    if Stage = PST_CLEAR_BACKGND then Stage := PST_CUSTOM;
  end;

  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 := 4;//penwidth;
    Bitmap.Canvas.Pen.Color := clBlue;
    Bitmap.Canvas.FrameRect(Rect(20, 20, imwidth-20, imheight-20));
    Bitmap.Canvas.TextOut(15, 32, 'ImgView');
  end;

  AddTransparentPNGLayer;

  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
  Edit3.Text:=IntToStr(BL.Index);
    BL.Free;
    raise;
  end;

  FDrawingLine := false;
  SwapBuffers32;
end;

procedure TForm5.FormDestroy(Sender: TObject);
begin
  bm32.Free;
  BL.Free;
end;

procedure TForm5.ImgViewPaintStage(Sender: TObject; Buffer: TBitmap32;
  StageNum: Cardinal);
const            //0..1
  Colors: array [Boolean] of TColor32 = ($FFFFFFFF, $FFB0B0B0);
var
  R: TRect;
  I, J: Integer;
  OddY: Integer;
  TilesHorz, TilesVert: Integer;
  TileX, TileY: Integer;
  TileHeight, TileWidth: Integer;
begin
  TileHeight := 13;
  TileWidth := 13;

  TilesHorz := Buffer.Width div TileWidth;
  TilesVert := Buffer.Height div TileHeight;
  TileY := 0;

  for J := 0 to TilesVert do
  begin
    TileX := 0;
    OddY := J and ;
    for I := 0 to TilesHorz do
    begin
      R.Left := TileX;
      R.Top := TileY;
      R.Right := TileX + TileWidth;
      R.Bottom := TileY + TileHeight;
      Buffer.FillRectS(R, Colors[I and  = OddY]);
      Inc(TileX, TileWidth);
    end;
    Inc(TileY, TileHeight);
  end;
end;

procedure TForm5.ImgViewResize(Sender: TObject);
begin
  OffsX := (ImgView.ClientWidth - imwidth) div 2;
  OffsY := (ImgView.ClientHeight - imheight) div 2;
  BL.Location := GR32.FloatRect(OffsX, OffsY, imwidth+OffsX, imheight+OffsY);
end;

procedure TForm5.LayerMouseDown(Sender: TObject; Buttons: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FStartPoint := Point(X-OffsX, Y-OffsY);
  FDrawingLine := true;
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-OffsX, FStartPoint.Y-OffsY);
      BL.Bitmap.Canvas.LineTo(X-OffsX, Y-OffsY);
  end;
end;

procedure TForm5.LayerMouseUp(Sender: TObject; Buttons: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDrawingLine := false;
  FEndPoint := Point(X-OffsX, Y-OffsY);
  AddLineToLayer;
  SwapBuffers32;
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
    TransparentBlt(
      BL.Bitmap.Canvas.Handle, 0, 0, BL.Bitmap.Width, BL.Bitmap.Height,
      bm32.Canvas.Handle, 0, 0, bm32.Width, bm32.Height, clWhite);
end;

procedure TForm5.AddTransparentPNGlayer;
var
  mypng:TPortableNetworkGraphic32;
  B : TBitmapLayer;
  P: TPoint;
  W, H: Single;
begin
      try
        mypng := TPortableNetworkGraphic32.Create;
        mypng.LoadFromFile('C:\Location\Of\ATransparentPNGFile.png');
        B := TBitmapLayer.Create(ImgView.Layers);
        with B do
        try
          mypng.AssignTo(B.Bitmap);
          Bitmap.DrawMode := dmBlend;
          with ImgView.GetViewportRect do
            P := ImgView.ControlToBitmap(GR32.Point((Right + Left) div 2, (Top + Bottom) div 2));
          W := Bitmap.Width * 0.5;
          H := Bitmap.Height * 0.5;
          Location := GR32.FloatRect(P.X - W, P.Y - H, P.X + W, P.Y + H);
          Scaled := True;
          OnMouseDown := LayerMouseDown;
        except
          Free;
          raise;
        end;
        Selection := B;
        Edit3.Text:=IntToStr(B.Index);
      finally
        mypng.Free;
      end;
end;

end.

我做错了什么？请测试上面的单元以了解我的意思。请记住添加一个 ImgView 并将其锚定到所有边距，然后在运行时最大化表单并尝试绘制线条...

编辑

上面绿色的图中，中间有一个矩形，更像是一个正方形（不是很明显），但仔细看还是可以看到的。

由于我的问题可能会被误解，请看下图

我只需要能够在 ImgView 中间的白色矩形（位图）中绘图。不知道怎么解释比较好。

让 rectangle/Bitmap 完全适合 ImgView 对我来说不是解决方案，因为那不是我项目的重点。

看看 Paint.net 并想象一下我的项目也做同样的事情（只是没那么复杂）。但原理是一样的：当你开始一个新项目时，你决定你的 document/image 的大小，然后你添加不同的图像作为图层，缩放和旋转它们，现在我想让用户画线特殊层（绘图层）内部但是一切都发生在该文档大小的范围内。例如在上图中，文档的大小为 A5 (100dpi)，缩放比例为 83%。

所以我的问题是我不能让用户在白色矩形（屏幕中间）之外绘制线条。所以他们的线路可以从这些边界开始并在那里结束。

我知道我的测试单元不是很干净。我粘贴了主项目中使用的一些功能，并迅速从中删除了一些与本示例无关的部分。 AddTransparentPng 过程仅允许测试将透明图像添加到 ImgView，这样我就可以测试绘图层是否未覆盖另一个可能的图层。

（Scaled 属性属于层 (B) 它在 'with B' 语句下。我删除了 With 'ImgView.Bitmap... Location' 语句所以它不会再打扰你了:) )

总之，不影响画线的代码请不要关注。该代码是需要注意的。

编辑如果我将图层的缩放设置为 true (Scaled:=true) 那么它会把所有东西都弄乱，如下图所示：

我仍然必须使用偏移量，但有点不同

谢谢

Answer 1

好的，我解决了。这是最终（相关）代码：

procedure TForm5.ImgViewResize(Sender: TObject);
begin
  OffsX := (ImgView.ClientWidth - imwidth) div 2;
  OffsY := (ImgView.ClientHeight - imheight) div 2;
  BL.Location := GR32.FloatRect(OffsX, OffsY, imwidth+OffsX, imheight+OffsY);
end;

procedure TForm5.SwapBuffers32;
begin
    TransparentBlt(
      BL.Bitmap.Canvas.Handle, 0, 0, BL.Bitmap.Width, BL.Bitmap.Height,
      bm32.Canvas.Handle, 0, 0, bm32.Width, bm32.Height, clWhite);
end;


procedure TForm5.LayerMouseDown(Sender: TObject; Buttons: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FStartPoint := Point(X-OffsX, Y-OffsY);
  FDrawingLine := true;
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-OffsX, Y-OffsY);
  end;
end;


procedure TForm5.LayerMouseUp(Sender: TObject; Buttons: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  FDrawingLine := false;
  FEndPoint := Point(X-OffsX, Y-OffsY);
  AddLineToLayer;
  SwapBuffers32;
end;

procedure TForm5.LayerOnPaint(Sender: TObject; Buffer: TBitmap32);
begin
  SwapBuffers32;
end;

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;

使用此代码，一切都按预期进行。画线只能发生在边界内

谢谢

Answer 2

错误一

在 LayerMouseMove() 中，您从 BL.Bitmap.Canvas.MoveTo() 中的 FStartPoint 中减去 OffsX 和 OffsY。 FStartPoint 已在 LayerMouseDown() 中调整。我告诉过你 "In the three Mouse procs adjust the X and Y arguments only to become X-OffsX and Y-OffsY." 注意 arguments only 这里的 LayerMouseMove() 更正：

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-OffsX, FStartPoint.Y-OffsY);
      BL.Bitmap.Canvas.MoveTo(FStartPoint.X, FStartPoint.Y);
      BL.Bitmap.Canvas.LineTo(X-OffsX, Y-OffsY);
  end;
end;

错误二

我还告诉过您将 if FDrawingLine then ... 条件添加到 LayerMouseUp() 以避免当鼠标按下发生在层外但鼠标松开发生在层内时出现伪线。更正后的 LayerMouseUp():

procedure TForm5.LayerMouseUp(Sender: TObject; Buttons: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  if FDrawingLine then
  begin
    FDrawingLine := false;
    FEndPoint := Point(X-OffsX, Y-OffsY);
    AddLineToLayer;
    SwapBuffers32;
  end;
end;

错误三

发布的代码与您的第一张图片显示的不一样。该图像看起来像您在 ImgViewResize() 中对 BL.Location := ... 行的注释。可能你这样做是因为 Error one。无论如何，使用如下 ImgViewResize 和上面的其他更正我得到如下图所示的结果。

procedure TForm5.ImgViewResize(Sender: TObject);
begin
  // centering the drawing area
  OffsX := (ImgView.ClientWidth - imwidth) div 2;
  OffsY := (ImgView.ClientHeight - imheight) div 2;
  BL.Location := GR32.FloatRect(OffsX, OffsY, imwidth+OffsX, imheight+OffsY);
end;

变量imwidth和imheight定义绘图区域的大小。如果更改这些，则需要重新计算 OffsX 和 OffsY，并且还需要调整后备缓冲区的大小 bm32。

角上的线条表示 window 中间的绘图区域（由 imwidth 和 imheight 定义）的范围。当 window 最大化时它也保持不变。

Delphi Graphics32 相对鼠标位置（到图层）

Delphi Graphics32 relative mouse position (to the layer)

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