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LazMapViewer: Implement zoomed preview tiles. Patch by Ekkehard Domning. Adapt drawing engines and full demo projects.

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git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@8835 8e941d3f-bd1b-0410-a28a-d453659cc2b4
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wp_xxyyzz
2023-06-13 15:39:47 +00:00
parent d9eb6e9065
commit 875a3a826d
12 changed files with 300 additions and 27 deletions
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59
components/lazmapviewer/source/mvcache.pas
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@@ -48,6 +48,7 @@ Type
destructor Destroy; override;
Procedure Add(MapProvider: TMapProvider; const TileId: TTileId; Stream: TMemoryStream);
Procedure GetFromCache(MapProvider: TMapProvider; const TileId: TTileId; out img: TLazIntfImage);
function GetPreviewFromCache(MapProvider: TMapProvider; var TileId: TTileId; out ARect: TRect): boolean;
function InCache(MapProvider: TMapProvider; const TileId: TTileId): Boolean;
property UseDisk: Boolean read FUseDisk write FUseDisk;
@@ -347,6 +348,64 @@ begin
end;
end;
{ When TileId is not yet in the cache, the function decreases zoom level and
returns the TileID of a tile which already is in the cache, and in ARect
the rectangle coordinates to get an upscaled preview of the originally
requested tile. The function returns true in this case.
If the requested tile already is in the cache, or no containing tile is found
the function returns false indicating that not preview image must be
generated. }
function TPictureCache.GetPreviewFromCache(MapProvider: TMapProvider;
var TileId: TTileId; out ARect: TRect): boolean;
var
ltid: TTileId;
xfrac, yfrac: Double;
lDeltaZoom: Integer;
w, px, py: Integer;
begin
Result := false;
ARect := Rect(0, 0, 0, 0);
if (TileId.Z < 0) or
(TileId.X < 0) or
(TileId.Y < 0) then exit;
if InCache(MapProvider, TileID) then
exit;
if TileId.Z <= 0 then
exit; // The whole earth as a preview, is simply the earth
// The "preview" is the part of the containing tile that covers the location of the wanted tile
// Every decrement of Zoom reduces the tile area by 4 (half of x and y direction)
// So incrementing Z and dividing X and Y in the Id will lead us to the containing tile
// The fraction of the division points to the location of the preview
// e.g 0.5 = right or lower half of the tile, when divided by 2
ltid := TileId;
lDeltaZoom := 1;
w := TILE_SIZE;
repeat
w := w shr 1;
dec(ltid.Z);
lDeltaZoom := lDeltaZoom shl 1;
xfrac := TileId.X / lDeltaZoom; // xfrac, yfrac contains the tile number
yfrac := TileId.Y / lDeltaZoom;
ltid.X := Trunc(xfrac);
ltid.Y := Trunc(yfrac);
if InCache(MapProvider, ltid) then
begin // We found a tile in the cache that contains the preview
xfrac := xfrac - ltid.X; //xfrac and yfrac calculated for the position in the tile from the cache
yfrac := yfrac - ltid.Y;
px := Trunc(xfrac * TILE_SIZE); //x and y are the percentage of the tile width
py := Trunc(yfrac * TILE_SIZE);
ARect := Rect(px, py, px+w, py+w);
TileID := ltid;
Result := true;
exit;
end;
until (w <= 1) or (ltid.Z <= 0);
end;
function TPictureCache.InCache(MapProvider: TMapProvider;
const TileId: TTileId): Boolean;
var