我正在基于带有TImage
控件的TScrollingWinControl
(以及从TScrollBox
复制的代码(制作一个简单的控件。我在某种程度上让缩放工作,但它不一定缩放到焦点 - 滚动条不会相应地更改以保持中心点清晰。
我希望能够告诉这个控件ZoomTo(const X, Y, ZoomBy: Integer);
告诉它缩放焦点的位置。因此,当它缩放时,我经过的坐标将保持"居中"。同时,我还需要有一个ZoomBy(const ZoomBy: Integer);
告诉它使其在当前视图中保持居中。
一种情况下,鼠标指向图像的特定点,当按住控制并向上滚动鼠标时,它应该放大,聚焦在鼠标指针上。另一方面,另一种情况是滑动控件以调整缩放级别,在这种情况下,它只需要保持当前视图的中心(不一定是图像的中心(聚焦。
问题是我的数学在这一点上迷失了,我无法找到正确的公式来调整这些滚动条。我尝试了几种不同的计算方法,似乎没有任何工作正常。
这是我控件的剥离版本。我删除了大部分只相关的东西,原始单位是 600 多行代码。下面最重要的程序是SetZoom(const Value: Integer);
unit JD.Imaging;
interface
uses
Windows, Classes, SysUtils, Graphics, Jpeg, PngImage, Controls, Forms,
ExtCtrls, Messages;
type
TJDImageBox = class;
TJDImageZoomEvent = procedure(Sender: TObject; const Zoom: Integer) of object;
TJDImageBox = class(TScrollingWinControl)
private
FZoom: Integer; //level of zoom by percentage
FPicture: TImage; //displays image within scroll box
FOnZoom: TJDImageZoomEvent; //called when zoom occurs
FZoomBy: Integer; //amount to zoom by (in pixels)
procedure MouseWheel(Sender: TObject; Shift: TShiftState;
WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
procedure SetZoom(const Value: Integer);
procedure SetZoomBy(const Value: Integer);
public
constructor Create(AOwner: TComponent); override;
published
property Zoom: Integer read FZoom write SetZoom;
property ZoomBy: Integer read FZoomBy write SetZoomBy;
property OnZoom: TJDImageZoomEvent read FOnZoom write FOnZoom;
end;
implementation
{ TJDImageBox }
constructor TJDImageBox.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
OnMouseWheel:= MouseWheel;
ControlStyle := [csAcceptsControls, csCaptureMouse, csClickEvents,
csSetCaption, csDoubleClicks, csPannable, csGestures];
AutoScroll := True;
TabStop:= True;
VertScrollBar.Tracking:= True;
HorzScrollBar.Tracking:= True;
Width:= 100;
Height:= 100;
FPicture:= TImage.Create(nil);
FPicture.Parent:= Self;
FPicture.AutoSize:= False;
FPicture.Stretch:= True;
FPicture.Proportional:= True;
FPicture.Left:= 0;
FPicture.Top:= 0;
FPicture.Width:= 1;
FPicture.Height:= 1;
FPicture.Visible:= False;
FZoom:= 100;
FZoomBy:= 10;
end;
destructor TJDImageBox.Destroy;
begin
FImage.Free;
FPicture.Free;
inherited;
end;
procedure TJDImageBox.MouseWheel(Sender: TObject; Shift: TShiftState;
WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
var
NewScrollPos: Integer;
begin
if ssCtrl in Shift then begin
if WheelDelta > 0 then
NewScrollPos := Zoom + 5
else
NewScrollPos:= Zoom - 5;
if NewScrollPos >= 5 then
Zoom:= NewScrollPos;
end else
if ssShift in Shift then begin
NewScrollPos := HorzScrollBar.Position - WheelDelta;
HorzScrollBar.Position := NewScrollPos;
end else begin
NewScrollPos := VertScrollBar.Position - WheelDelta;
VertScrollBar.Position := NewScrollPos;
end;
Handled := True;
end;
procedure TJDImageBox.SetZoom(const Value: Integer);
var
Perc: Single;
begin
FZoom := Value;
if FZoom < FZoomBy then
FZoom:= FZoomBy;
Perc:= FZoom / 100;
//Resize picture to new zoom level
FPicture.Width:= Trunc(FImage.Width * Perc);
FPicture.Height:= Trunc(FImage.Height * Perc);
//Move scroll bars to properly position the center of the view
//This is where I don't know how to calculate the 'center'
//or by how much I need to move the scroll bars.
HorzScrollBar.Position:= HorzScrollBar.Position - (FZoomBy div 2);
VertScrollBar.Position:= VertScrollBar.Position - (FZoomBy div 2);
if assigned(FOnZoom) then
FOnZoom(Self, FZoom);
end;
procedure TJDImageBox.SetZoomBy(const Value: Integer);
begin
if FZoomBy <> Value then begin
FZoomBy := EnsureRange(Value, 1, 100);
Paint;
end;
end;
end.
目前尚不清楚在传递给"ZoomBy(("时,您想引用X,Y的什么。我假设您已经为图像放置了一个"OnMouseDown"处理程序,坐标是指您单击图像的位置,即它们不相对于滚动框坐标。如果不是这样,您可以自己调整它。
让我们暂时忘记缩放,让我们的任务将我们单击滚动框中的图像的点居中。很简单,我们知道滚动框的中心位于(ScrollBox.ClientWidth/2,ScrollBox.ClientHeight/2(。水平思考,我们想向上滚动到一个点,这样,如果我们向它添加 ClientWidth/2,它将是我们的点击点:
procedure ScrollTo(CenterX, CenterY: Integer);
begin
ScrollBox.HorzScrollBar.Position := CenterX - Round(ScrollBox.ClientWidth / 2);
ScrollBox.VertScrollBar.Position := CenterY - Round(ScrollBox.ClientHeight / 2);
end;
现在考虑缩放。我们所要做的就是相应地计算 X、Y 位置,滚动框的大小不会改变。 CenterX := Center.X * ZoomFactor
.但请注意,这里的"ZoomFactor"不是有效缩放,而是单击图像时将应用的缩放。我将使用图像的前后尺寸来确定:
procedure ZoomTo(CenterX, CenterY, ZoomBy: Integer);
var
OldWidth, OldHeight: Integer;
begin
OldWidth := FImage.Width;
OldHeight := FImage.Height;
// zoom the image, we have new image size and scroll range
CenterX := Round(CenterX * FImage.Width / OldWidth);
ScrollBox.HorzScrollBar.Position := CenterX - Round(ScrollBox.ClientWidth / 2);
CenterY := Round(CenterY * FImage.Height / OldHeight);
ScrollBox.VertScrollBar.Position := CenterY - Round(ScrollBox.ClientHeight / 2);
end;
当然,您可以将它们重构为一行,以便仅调用一次 Round(( 以减少舍入误差。
我相信你可以自己从这里锻炼。