如何在正确保持纵横比的情况下进行缩放
Posted
技术标签:
【中文标题】如何在正确保持纵横比的情况下进行缩放【英文标题】：How To Zoom with keeping aspect ratio correctly 【发布时间】：2012-06-19 00:09:39 【问题描述】：这就是我的目标。 使用鼠标左键滚动图像，鼠标右键滚动 选择缩放矩形并双击以恢复完全缩放。
我目前很累，到目前为止发现它与我加载图像或显示图像的方式无关，而是与它的绘画方式有关。无论窗体或源图像的形状如何，屏幕上的图像始终填充控件的客户区，因此不可能保留纵横比。我不确定如何更改或保持纵横比。因此给了我一张干净漂亮的照片。
我正在发布我的 ZImage 单元的整个代码虽然我认为问题出在 Zimage.paint 或 Zimage.mouseup 但想如果您需要查看其中一个函数中的一个函数，将其全部发布会有所帮助.
unit ZImage;
interface
uses
Windows, Messages, SysUtils,jpeg, Classes, Graphics, Controls, Forms, Dialogs,
ExtCtrls;
type
TZImage = class(TGraphicControl)
private
FBitmap : Tbitmap;
PicRect : TRect;
ShowRect : TRect;
FShowBorder : boolean;
FBorderWidth : integer;
FForceRepaint : boolean;
FMouse : (mNone, mDrag, mZoom);
FProportional : boolean;
FDblClkEnable : boolean;
FLeft :integer;
FRight :integer;
FTop :integer;
FBottom :integer;
startx, starty,
oldx, oldy : integer;
procedure SetShowBorder(s:boolean);
procedure SetBitmap(b:TBitmap);
procedure SetBorderWidth(w:integer);
procedure SetProportional(b:boolean);
protected
procedure Paint; override;
procedure MouseDown(Button: TMouseButton; Shift: TShiftState;
X, Y: Integer); override;
procedure MouseMove(Shift: TShiftState; X, Y: Integer); override;
procedure MouseUp(Button: TMouseButton; Shift: TShiftState;
X, Y: Integer); override;
public
constructor Create(AOwner:TComponent); override;
destructor Destroy; override;
procedure DblClick; override;
published
procedure zoom(Endleft,EndRight,EndTop,EndBottom:integer);
property ValueLeft : integer read FLeft write FLeft;
property ValueRight : Integer read FRight write FRight;
Property ValueTop : Integer read FTop write FTop;
Property ValueBottom : Integer read FBottom write FBottom;
property ShowBorder : boolean
read FShowBorder
write SetShowBorder default true;
property KeepAspect : boolean
read FProportional
write SetProportional default true;
property Bitmap : TBitmap
read FBitmap
write Setbitmap;
property BorderWidth : integer
read FBorderWidth
write SetBorderWidth default 7;
property ForceRepaint : boolean
read FForceRepaint
write FForceRepaint default true;
property DblClkEnable : boolean
read FDblClkEnable
write FDblClkEnable default False;
property Align;
property Width;
property Height;
property Top;
property Left;
property Visible;
property Hint;
property ShowHint;
end;
procedure Register;
implementation
//This is the basic create options.
constructor TZImage.Create(AOwner:TComponent);
begin
inherited;
FShowBorder:=True;
FBorderWidth:=7;
FMouse:=mNone;
FForceRepaint:=true; //was true
FDblClkEnable:=False;
FProportional:=true; //was true
Width:=100; Height:=100;
FBitmap:=Tbitmap.Create;
FBitmap.Width:=width;
FBitmap.height:=Height;
ControlStyle:=ControlStyle+[csOpaque];
autosize:= false;
//Scaled:=false;
end;
//basic destroy frees the FBitmap
destructor TZImage.Destroy;
begin
FBitmap.Free;
inherited;
end;
//This was a custom zoom i was using to give the automated zoom effect
procedure TZimage.zoom(Endleft,EndRight,EndTop,EndBottom:integer);
begin
while ((Endbottom <> picrect.bottom) or (Endtop <> picrect.top)) or ((endleft <> picrect.left) or (endright <> picrect.right)) do
begin
if picrect.left > endleft then
picrect.left := picrect.left -1;
if picrect.left < endleft then //starting
picrect.left := picrect.left +1;
if picrect.right > endright then //starting
picrect.right := picrect.right -1;
if picrect.right < endright then
picrect.right := picrect.right +1;
if picrect.top > endtop then
picrect.top := picrect.top -1;
if picrect.top < endtop then //starting
picrect.top := picrect.top +1;
if picrect.bottom > endbottom then //starting
picrect.bottom := picrect.bottom -1;
if picrect.bottom < endbottom then
picrect.bottom := picrect.bottom +1;
self.refresh;
end;
end;
//this is the custom paint I know if i put
//Canvas.Draw(0,0,FBitmap); as the methond it displays
//perfect but the zoom option is gone of course and
//i need the Zoom.
procedure TZImage.Paint;
var buf:TBitmap;
coef,asps,aspp:Double;
sz,a : integer;
begin
buf:=TBitmap.Create;
buf.Width:=Width;
buf.Height:=Height;
if not FShowBorder
then ShowRect:=ClientRect
else ShowRect:=Rect(ClientRect.Left,ClientRect.Top,
ClientRect.Right-FBorderWidth,
ClientRect.Bottom-FBorderWidth);
ShowRect:=ClientRect;
with PicRect do begin
if Right=0 then Right:=FBitmap.Width;
if Bottom=0 then Bottom:=FBitmap.Height;
end;
buf.Canvas.CopyMode:=cmSrcCopy;
buf.Canvas.CopyRect(ShowRect,FBitmap.Canvas,PicRect);
Canvas.CopyMode:=cmSrcCopy;
Canvas.Draw(0,0,buf);
buf.Free;
end;
procedure TZImage.MouseDown(Button: TMouseButton; Shift: TShiftState;
X, Y: Integer);
begin
// if mbLeft<>Button then Exit;
if not PtInRect(ShowRect,Point(X,Y)) and
not PtInRect(Rect(ShowRect.Right,ShowRect.Bottom,
Width,Height),Point(X,Y)) then Exit;
if PtInRect(Rect(ShowRect.Right,ShowRect.Bottom,
Width,Height),Point(X,Y)) then begin
DblClick;
Exit;
end;
//here click is in the picture area only
startx:=x; oldx:=x;
starty:=y; oldy:=y;
if mbRight=Button then begin
MouseCapture:=True;
FMouse:=mZoom;
Canvas.Pen.Mode:=pmNot;
end else begin
FMouse:=mDrag;
Screen.Cursor:=crHandPoint;
end;
end;
function Min(a,b:integer):integer;
begin
if a<b then Result:=a else Result:=b;
end;
function Max(a,b:integer):integer;
begin
if a<b then Result:=b else Result:=a;
end;
procedure TZImage.MouseMove(Shift: TShiftState; X, Y: Integer);
var d,s:integer;
coef:Double;
begin
if FMouse=mNone then Exit;
if FMouse=mZoom then begin
Canvas.DrawFocusRect(Rect(Min(startx,oldx),Min(starty,oldy),Max(startx,oldx),Max(starty,oldy)));
oldx:=x; oldy:=y;
Canvas.DrawFocusRect(Rect(Min(startx,oldx),Min(starty,oldy),Max(startx,oldx),Max(starty,oldy)));
end;
if FMouse=mDrag then begin
//horizontal movement
coef:=(PicRect.Right-PicRect.Left)/(ShowRect.Right-ShowRect.Left);
d:=Round(coef*(x-oldx));
s:=PicRect.Right-PicRect.Left;
if d>0 then begin
if PicRect.Left>=d then begin
PicRect.Left:=PicRect.Left-d;
PicRect.Right:=PicRect.Right-d;
end else begin
PicRect.Left:=0;
PicRect.Right:=PicRect.Left+s;
end;
end;
if d<0 then begin
if PicRect.Right<FBitmap.Width+d then begin
PicRect.Left:=PicRect.Left-d;
PicRect.Right:=PicRect.Right-d;
end else begin
PicRect.Right:=FBitmap.Width;
PicRect.Left:=PicRect.Right-s;
end;
end;
//vertical movement
coef:=(PicRect.Bottom-PicRect.Top)/(ShowRect.Bottom-ShowRect.Top);
d:=Round(coef*(y-oldy));
s:=PicRect.Bottom-PicRect.Top;
if d>0 then begin
if PicRect.Top>=d then begin
PicRect.Top:=PicRect.Top-d;
PicRect.Bottom:=PicRect.Bottom-d;
end else begin
PicRect.Top:=0;
PicRect.Bottom:=PicRect.Top+s;
end;
end;
There was a bug in the fragment below. Thanks to all, who reported this bug to me
if d<0 then begin
if PicRect.Bottom<FBitmap.Height+d then begin
PicRect.Top:=PicRect.Top-d;
PicRect.Bottom:=PicRect.Bottom-d;
end else begin
PicRect.Bottom:=FBitmap.Height;
PicRect.Top:=PicRect.Bottom-s;
end;
end;
oldx:=x; oldy:=y;
if FForceRepaint then Repaint
else Invalidate;
end;
end;
procedure TZImage.MouseUp(Button: TMouseButton; Shift: TShiftState;
X, Y: Integer);
var coef:Double;
t:integer;
left,right,top,bottom : integer;
begin
if FMouse=mNone then Exit;
if x>ShowRect.Right then x:=ShowRect.Right;
if y>ShowRect.Bottom then y:=ShowRect.Bottom;
if FMouse=mZoom then begin //calculate new PicRect
t:=startx;
startx:=Min(startx,x);
x:=Max(t,x);
t:=starty;
starty:=Min(starty,y);
y:=Max(t,y);
FMouse:=mNone;
MouseCapture:=False;
//enable the following if you want to zoom-out by dragging in the opposite direction
if Startx>x then begin
DblClick;
Exit;
end;
if Abs(x-startx)<5 then Exit;
//showmessage('picrect Left='+inttostr(picrect.Left)+' right='+inttostr(picrect.Right)+' top='+inttostr(picrect.Top)+' bottom='+inttostr(picrect.Bottom));
//startx and start y is teh starting x/y of the selected area
//x and y is the ending x/y of the selected area
if (x - startx < y - starty) then
begin
while (x - startx < y - starty) do
begin
x := x + 100;
startx := startx - 100;
end;
end
else if (x - startx > y - starty) then
begin
while (x - startx > y - starty) do
begin
y := y + 100;
starty := starty - 100;
end;
end;
//picrect is the size of whole area
//PicRect.top and left are 0,0
//IFs were added in v.1.2 to avoid zero-divide
if (PicRect.Right=PicRect.Left)
then
coef := 100000
else
coef:=ShowRect.Right/(PicRect.Right-PicRect.Left); //if new screen coef= 1
left:=Round(PicRect.Left+startx/coef);
Right:=Left+Round((x-startx)/coef);
if (PicRect.Bottom=PicRect.Top)
then
coef := 100000
else
coef:=ShowRect.Bottom/(PicRect.Bottom-PicRect.Top);
Top:=Round(PicRect.Top+starty/coef);
Bottom:=Top+Round((y-starty)/coef);
//showmessage(inttostr(left)+' '+inttostr(Right)+' '+inttostr(top)+' '+inttostr(bottom));
zoom(left,right,top,bottom);
ValueLeft := left;
ValueRight := Right;
ValueTop := top;
ValueBottom := bottom;
end;
if FMouse=mDrag then begin
FMouse:=mNone;
Canvas.Pen.Mode:=pmCopy;
Screen.Cursor:=crDefault;
end;
Invalidate;
end;
procedure TZImage.DblClick;
begin
zoom(0,FBitMap.Width,0,FBitMap.Height);
ValueLeft := 0;
ValueRight := FBitMap.Width;
ValueTop := 0;
ValueBottom := FBitMap.Height;
//PicRect:=Rect(0,0,FBitmap.Width,FBitmap.Height);
Invalidate;
end;
procedure TZImage.SetBitmap(b:TBitmap);
begin
FBitmap.Assign(b);
PicRect:=Rect(0,0,b.Width, b.Height);
Invalidate;
end;
procedure TZImage.SetBorderWidth(w:integer);
begin
FBorderWidth:=w;
Invalidate;
end;
procedure TZImage.SetShowBorder(s:boolean);
begin
FShowBorder:=s;
Invalidate;
end;
procedure TZImage.SetProportional(b:boolean);
begin
FProportional:=b;
Invalidate;
end;
procedure Register;
begin
RegisterComponents('Custom', [TZImage]);
end;
end.
使用此代码，您可以注册组件 ZImage 并查看它是如何运行的。如果需要的话
【问题讨论】：
我必须感谢你的坚持。 :-) 我现在会崩溃并花钱购买一个好的，便宜的图像库，而不是重新发明***。 这有什么好玩的……因为我这样做是为了好玩（听起来很疯狂）我喜欢学习新东西……只是自学有时你会遇到一些没有意义的东西……一旦我在一些帮助下弄清楚了这一点：我不再需要重新审视这个问题。 按照这个逻辑，你不应该使用.jpg 图像；您应该使用自己的图像格式，并且不应该使用 Delphi，而应该使用自己的 IDE 和语言。 :-) 适合工作的适当工具 - 您的时间难道不能更好地用于证明更好的用户界面体验而不是图像缩放/缩放吗？
+1 表示没有发布少量的 sn-ps 代码（这使得更难理解和查看被问到的问题）。
@Glen，您能否改写您的问题以反映接受的答案（控件）的作用？我的意思是提到动画缩放到选择。我想许多访问此问答的人可能想知道为什么我在这里放一个赏金并评论这值得关注，但这（主要）是为了努力和缩放动画。谢谢！
【参考方案1】：
这个问题很清楚，但我认为回答这个问题的问题是如何不重写完整的代码以使您可以理解。而且由于我更擅长编码然后解释，所以我做到了。
我认为您正在搜索类似以下内容：
unit ZImage2;
interface
uses
Windows, Messages, Classes, Controls, Graphics, StdCtrls, ExtCtrls, Math;
const
DefAnimDuration = 500;
type
TZImage = class(TGraphicControl)
private
FAlignment: TAlignment;
FAnimDuration: Cardinal;
FAnimRect: TRect;
FAnimStartTick: Cardinal;
FAnimTimer: TTimer;
FBuffer: TBitmap;
FCropRect: TRect;
FImgRect: TRect;
FLayout: TTextLayout;
FPicture: TPicture;
FPrevCropRect: TRect;
FProportional: Boolean;
FProportionalCrop: Boolean;
FScale: Single;
FSelColor: TColor;
FSelecting: Boolean;
FSelPoint: TPoint;
FSelRect: TRect;
procedure Animate(Sender: TObject);
function HasGraphic: Boolean;
procedure PictureChanged(Sender: TObject);
procedure RealignImage;
procedure SetAlignment(Value: TAlignment);
procedure SetLayout(Value: TTextLayout);
procedure SetPicture(Value: TPicture);
procedure SetProportional(Value: Boolean);
procedure UpdateBuffer;
protected
function CanAutoSize(var NewWidth, NewHeight: Integer): Boolean; override;
procedure ChangeScale(M: Integer; D: Integer); override;
procedure DblClick; override;
procedure MouseDown(Button: TMouseButton; Shift: TShiftState; X,
Y: Integer); override;
procedure MouseMove(Shift: TShiftState; X, Y: Integer); override;
procedure MouseUp(Button: TMouseButton; Shift: TShiftState; X,
Y: Integer); override;
procedure Paint; override;
procedure Resize; override;
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
procedure Reset;
function ScreenToGraphic(R: TRect): TRect;
procedure Zoom(const ACropRect: TRect);
procedure ZoomSelection(const ASelRect: TRect);
published
property Alignment: TAlignment read FAlignment write SetAlignment
default taLeftJustify;
property AnimDuration: Cardinal read FAnimDuration write FAnimDuration
default DefAnimDuration;
property Layout: TTextLayout read FLayout write SetLayout default tlTop;
property Picture: TPicture read FPicture write SetPicture;
property Proportional: Boolean read FProportional write SetProportional
default False;
property ProportionalCrop: Boolean read FProportionalCrop
write FProportionalCrop default True;
property SelColor: TColor read FSelColor write FSelColor default clWhite;
published
property Align;
property Anchors;
property AutoSize;
property Color;
end;
implementation
function FitRect(const Boundary: TRect; Width, Height: Integer;
CanGrow: Boolean; HorzAlign: TAlignment; VertAlign: TTextLayout): TRect;
var
W: Integer;
H: Integer;
Scale: Single;
Offset: TPoint;
begin
Width := Max(1, Width);
Height := Max(1, Height);
W := Boundary.Right - Boundary.Left;
H := Boundary.Bottom - Boundary.Top;
if CanGrow then
Scale := Min(W / Width, H / Height)
else
Scale := Min(1, Min(W / Width, H / Height));
Result := Rect(0, 0, Round(Width * Scale), Round(Height * Scale));
case HorzAlign of
taLeftJustify:
Offset.X := 0;
taCenter:
Offset.X := (W - Result.Right) div 2;
taRightJustify:
Offset.X := W - Result.Right;
end;
case VertAlign of
tlTop:
Offset.Y := 0;
tlCenter:
Offset.Y := (H - Result.Bottom) div 2;
tlBottom:
Offset.Y := H - Result.Bottom;
end;
OffsetRect(Result, Boundary.Left + Offset.X, Boundary.Top + Offset.Y);
end;
function NormalizeRect(const Point1, Point2: TPoint): TRect;
begin
Result.Left := Min(Point1.X, Point2.X);
Result.Top := Min(Point1.Y, Point2.Y);
Result.Right := Max(Point1.X, Point2.X);
Result.Bottom := Max(Point1.Y, Point2.Y);
end;
TZImage
procedure TZImage.Animate(Sender: TObject);
var
Done: Single;
begin
Done := (GetTickCount - FAnimStartTick) / FAnimDuration;
if Done >= 1.0 then
begin
FAnimTimer.Enabled := False;
FAnimRect := FCropRect;
end
else
with FPrevCropRect do
FAnimRect := Rect(
Left + Round(Done * (FCropRect.Left - Left)),
Top + Round(Done * (FCropRect.Top - Top)),
Right + Round(Done * (FCropRect.Right - Right)),
Bottom + Round(Done * (FCropRect.Bottom - Bottom)));
UpdateBuffer;
RealignImage;
Invalidate;
end;
function TZImage.CanAutoSize(var NewWidth, NewHeight: Integer): Boolean;
begin
Result := True;
if not (csDesigning in ComponentState) or HasGraphic then
begin
if Align in [alNone, alLeft, alRight] then
NewWidth := Round(FScale * FPicture.Width);
if Align in [alNone, alTop, alBottom] then
NewHeight := Round(FScale * FPicture.Height);
end;
end;
procedure TZImage.ChangeScale(M, D: Integer);
var
SaveAnchors: TAnchors;
begin
SaveAnchors := Anchors;
Anchors := [akLeft, akTop];
FScale := FScale * M / D;
inherited ChangeScale(M, D);
Anchors := SaveAnchors;
end;
constructor TZImage.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
ControlStyle := [csCaptureMouse, csClickEvents, csOpaque, csDoubleClicks];
FAnimTimer := TTimer.Create(Self);
FAnimTimer.Interval := 15;
FAnimTimer.OnTimer := Animate;
FAnimDuration := DefAnimDuration;
FBuffer := TBitmap.Create;
FPicture := TPicture.Create;
FPicture.OnChange := PictureChanged;
FProportionalCrop := True;
FScale := 1.0;
FSelColor := clWhite;
end;
procedure TZImage.DblClick;
begin
if not HasGraphic then
Reset
else
Zoom(Rect(0, 0, FPicture.Width, FPicture.Height));
inherited DblClick;
end;
destructor TZImage.Destroy;
begin
FPicture.Free;
FBuffer.Free;
inherited Destroy;
end;
function TZImage.HasGraphic: Boolean;
begin
Result := (Picture.Width > 0) and (Picture.Height > 0);
end;
procedure TZImage.MouseDown(Button: TMouseButton; Shift: TShiftState; X,
Y: Integer);
begin
if (Button = mbRight) and HasGraphic and PtInRect(FImgRect, Point(X, Y)) then
begin
FSelPoint.X := X;
FSelPoint.Y := Y;
FSelRect := Rect(X, Y, X, Y);
FSelecting := True;
Canvas.Brush.Color := FSelColor;
Canvas.DrawFocusRect(FSelRect);
end;
inherited MouseDown(Button, Shift, X, Y);
end;
procedure TZImage.MouseMove(Shift: TShiftState; X, Y: Integer);
const
HorzAlign: array[Boolean] of TAlignment = (taLeftJustify, taRightJustify);
VertAlign: array[Boolean] of TTextLayout = (tlTop, tlBottom);
begin
if FSelecting and PtInRect(FImgRect, Point(X, Y)) then
begin
Canvas.DrawFocusRect(FSelRect);
FSelRect := NormalizeRect(FSelPoint, Point(X, Y));
if (not FProportionalCrop) then
FSelRect := FitRect(FSelRect, FPicture.Graphic.Width,
FPicture.Graphic.Height, True, HorzAlign[X < FSelPoint.X],
VertAlign[Y < FSelPoint.Y]);
Canvas.DrawFocusRect(FSelRect);
end;
inherited MouseMove(Shift, X, Y);
end;
procedure TZImage.MouseUp(Button: TMouseButton; Shift: TShiftState; X,
Y: Integer);
begin
if FSelecting then
begin
FSelecting := False;
Canvas.DrawFocusRect(FSelRect);
if (Abs(X - FSelPoint.X) > Mouse.DragThreshold) or
(Abs(Y - FSelPoint.Y) > Mouse.DragThreshold) then
ZoomSelection(FSelRect);
end;
inherited MouseUp(Button, Shift, X, Y);
end;
procedure TZImage.Paint;
begin
Canvas.Brush.Color := Color;
if HasGraphic then
begin
Canvas.StretchDraw(FImgRect, FBuffer);
if FSelecting then
Canvas.DrawFocusRect(FSelRect);
with FImgRect do
ExcludeClipRect(Canvas.Handle, Left, Top, Right, Bottom);
end;
Canvas.FillRect(Canvas.ClipRect);
end;
procedure TZImage.PictureChanged(Sender: TObject);
begin
Reset;
end;
procedure TZImage.RealignImage;
begin
if not HasGraphic then
FImgRect := Rect(0, 0, 0, 0)
else if FProportional then
FImgRect := ClientRect
else
FImgRect := FitRect(ClientRect, FBuffer.Width, FBuffer.Height, True,
FAlignment, FLayout);
end;
procedure TZImage.Reset;
begin
FCropRect := Rect(0, 0, FPicture.Width, FPicture.Height);
FAnimRect := FCropRect;
UpdateBuffer;
RealignImage;
Invalidate;
end;
procedure TZImage.Resize;
begin
RealignImage;
inherited Resize;
end;
function TZImage.ScreenToGraphic(R: TRect): TRect;
var
CropWidth: Integer;
CropHeight: Integer;
ImgWidth: Integer;
ImgHeight: Integer;
begin
CropWidth := FCropRect.Right - FCropRect.Left;
CropHeight := FCropRect.Bottom - FCropRect.Top;
ImgWidth := FImgRect.Right - FImgRect.Left;
ImgHeight := FImgRect.Bottom - FImgRect.Top;
IntersectRect(R, R, FImgRect);
OffsetRect(R, -FImgRect.Left, -FImgRect.Top);
Result := Rect(
FCropRect.Left + Round(CropWidth * (R.Left / ImgWidth)),
FCropRect.Top + Round(CropHeight * (R.Top / ImgHeight)),
FCropRect.Left + Round(CropWidth * (R.Right / ImgWidth)),
FCropRect.Top + Round(CropHeight * (R.Bottom / ImgHeight)));
end;
procedure TZImage.SetAlignment(Value: TAlignment);
begin
if FAlignment <> Value then
begin
FAlignment := Value;
RealignImage;
Invalidate;
end;
end;
procedure TZImage.SetLayout(Value: TTextLayout);
begin
if FLayout <> Value then
begin
FLayout := Value;
RealignImage;
Invalidate;
end;
end;
procedure TZImage.SetPicture(Value: TPicture);
begin
FPicture.Assign(Value);
end;
procedure TZImage.SetProportional(Value: Boolean);
begin
if FProportional <> Value then
begin
FProportional := Value;
RealignImage;
Invalidate;
end;
end;
procedure TZImage.UpdateBuffer;
begin
if HasGraphic then
begin
FBuffer.Width := FAnimRect.Right - FAnimRect.Left;
FBuffer.Height := FAnimRect.Bottom - FAnimRect.Top;
FBuffer.Canvas.Draw(-FAnimRect.Left, -FAnimRect.Top, FPicture.Graphic);
end;
end;
procedure TZImage.Zoom(const ACropRect: TRect);
begin
if HasGraphic then
begin
FPrevCropRect := FAnimRect;
FCropRect := ACropRect;
if FAnimDuration = 0 then
begin
FAnimRect := FCropRect;
UpdateBuffer;
RealignImage;
Invalidate;
end
else
begin
FAnimStartTick := GetTickCount;
FAnimTimer.Enabled := True;
end;
end;
end;
procedure TZImage.ZoomSelection(const ASelRect: TRect);
begin
Zoom(ScreenToGraphic(ASelRect));
end;
end.
示例代码：
procedure TForm1.FormCreate(Sender: TObject);
begin
FImage := TZImage.Create(Self);
FImage.SetBounds(10, 10, 200, 300);
FImage.Picture.LoadFromFile('D:\Pictures\Mona_Lisa.jpg');
FImage.Alignment := taCenter;
FImage.Layout := tlCenter;
FImage.AutoSize := True;
FImage.Parent := Self;
end;
【讨论】：
当我运行它时，我得到了引发异常类 RReaError 的消息'Property Bitmap.Data 不存在' 在哪一行？它在这里用 D7 和 XE2 编译得很好。 我想这是因为我试图用这个代码覆盖一个旧的注册组件代码。我创建了一个新表单并使用此代码添加了新单元。我目前有3个问题不知道您是否解决了这个问题？首先，我在 FImage.Layout 的 tlCenter 上收到错误未定义标识符：= tlCenter;其次，如果我双击它只会缩小到目前为止。它不适合整个图像，可能是由于我的图像大小？第三，我不能拖动图像。我不知道您是否添加了问题 2 或 3。如果不是，请尝试使其正常工作，但要注意以防您确实添加了它们。除此之外，它工作得很好！ 这个问答的 325 次浏览就足够了，赏金现在是你的 :-) @TLama 哇，太慷慨了。谢谢！以上是关于如何在正确保持纵横比的情况下进行缩放的主要内容，如果未能解决你的问题，请参考以下文章
如何在 Firefox 中不尊重纵横比的情况下缩放 SVG 背景图像？
如何使 YouTube 播放器缩放到页面宽度，同时保持纵横比？