在自定义地图控件中缩放和平移-Zoomingandpanninginacustommapcontrol

I'm wondering if anyone can help me with this or at least provide pointers in the right direction. I can post code if required however, due to the nature of the question, there is a lot of it and hence why I haven't so far.

我想知道是否有人可以帮助我,或至少提供正确方向的指示。如果需要,我可以发布代码,但由于问题的性质,有很多,因此我没有到目前为止。

I have a custom control which represents a "map". On this "map" I can draw specific glyphs at specific latitude and longitude's. I use GPS behind the scenes to obtain a geographic fix location which I then feed into the map as its origin position.

我有一个代表“地图”的自定义控件。在这张“地图”上,我可以在特定的纬度和经度上绘制特定的字形。我在后台使用GPS获取地理定位位置,然后我将其作为原点位置输入地图。

All objects drawn to the map have their lat/long positions converted to easting and northings (using an algorithm similar to the Google Maps/Bing projection) before being converted to screen pixels.

在转换为屏幕像素之前,绘制到地图的所有对象都将其纬度/长度位置转换为东向和北向(使用类似于Google Maps / Bing投影的算法)。

I take the centre of my "map" control client region as the reference screen position. When the "map" is panned, I store the delta mouse movement as an offset which when added to the reference position, gives me the location to start drawing my origin grid (this is also where the GPS position links in).

我将“地图”控制客户区域的中心作为参考屏幕位置。当平移“地图”时,我将增量鼠标移动存储为偏移量,当添加到参考位置时,为我提供开始绘制原点网格的位置(这也是GPS位置链接的位置)。

I hope this is making sense so far...

我希望到目前为止这是有意义的......

Now, all works well so far - I can draw objects at specific latitude and longitudes and they all appear in their correct locations relative to the centre of the origin grid.

现在,到目前为止一切运行良好 - 我可以在特定纬度和经度绘制物体,它们都出现在相对于原始网格中心的正确位置。

The issue which I can't seem to get my head around is how to zoom the map and focus on a specific area - like when using Google Maps/Google Earth, the position underneath the cursor at the point of zooming stays the same. Crudely, I use a zoom system which just increases or decreases the number of metres represented by 100 screen pixels (I'd like a more logarithmic style zoom but that will come later).

我似乎无法理解的问题是如何缩放地图并专注于特定区域 - 就像使用谷歌地图/谷歌地球时,光标下方缩放点的位置保持不变。粗略地说,我使用的是一个变焦系统,它只增加或减少100个屏幕像素所代表的米数(我想要一个更对数的样式变焦,但稍后会出现)。

What happens when I zoom in is that zooming always keeps my grid origin in the same position (this is because I use an offset for panning the map - and the offset isn't affected by zoom) however I have no idea how to think through the more correct zoom system.

当我放大时会发生的变化是缩放始终使我的网格原点保持在相同位置(这是因为我使用偏移来平移地图 - 并且偏移不受缩放影响)但是我不知道如何思考更正确的变焦系统。

I appreciate that this is a lot of text with no code - I can post code but like I said, there is a heck of a lot of it! I'm also sure that I've not explained my scenario very well but I'd appreciate any help at all.

我很欣赏这是很多没有代码的文本 - 我可以发布代码,但就像我说的那样,有很多内容!我也很确定我没有很好地解释我的情景,但我会感激任何帮助。

1 个解决方案

type
  TMapCOntrol= class(TCustomControl)
  protected
    procedure Paint; override;
  public
    Glyph: TBitmap;
    //These are known, in GPS-coördinate units:
    MapRect: TRectF;
    ZoomFactor: Single;
    ZoomOrigin: TPointF;
    GlyphOrigin: TPointF;
  end;

procedure TMapControl.Paint;
var
  ZoomWidth: Single;
  ZoomHeight: Single;
  ZoomRect: TRectF;
  Scale: Single;
  GlyphPoint: TPoint;
begin
  // Calculation in GPS units:
  ZoomWidth := MapRect.Width * ZoomFactor;
  ZoomHeight := ZoomWidth * ClientHeight / ClientWidth;
  ZoomRect.Left := ZoomOrigin.X - ZoomWidth / 2;
  ZoomRect.Top := ZoomOrigin.Y - ZoomHeight / 2;
  // Not required for calculation, but for future convenience:
  ZoomRect.Width := ZoomWidth;
  ZoomRect.Height := ZoomHeight;
  // Calculation in device units:
  Scale := ZoomWidth / ClientWidth;  
  GlyphPoint.X := Round((GlyphOrigin.X - ZoomRect.Left) / Scale);
  GlyphPoint.Y := Round((GlyphOrigin.Y - ZoomRect.Top) / Scale);
  Canvas.Draw(GlyphPoint.X - Glyph.Width div 2,
    GlyphPoint.Y - Glyph.Height div 2, Glyph);
end;