private static void DrawWebMercatorTilesToRasterCanvas(
SKCanvas outputCanvas,
int width,
int height,
Models.Bounds boundingBox,
IList <Models.TileDataset> sourceTiles,
uint backgroundColor,
int tileSize)
{
var zoom = sourceTiles[0].Z;
var tileMinX = sourceTiles.Min(t => t.X);
var tileMinY = sourceTiles.Min(t => t.Y);
var tilesCountX = sourceTiles.Max(t => t.X) - tileMinX + 1;
var tilesCountY = sourceTiles.Max(t => t.Y) - tileMinY + 1;
var canvasWidth = tilesCountX * tileSize;
var canvasHeight = tilesCountY * tileSize;
var imageInfo = new SKImageInfo(
width: canvasWidth,
height: canvasHeight,
colorType: SKColorType.Rgba8888,
alphaType: SKAlphaType.Premul);
using var surface = SKSurface.Create(imageInfo);
using var canvas = surface.Canvas;
canvas.Clear(new SKColor(backgroundColor));
// Draw all tiles
foreach (var sourceTile in sourceTiles)
{
var offsetX = (sourceTile.X - tileMinX) * tileSize;
var offsetY = (sourceTile.Y - tileMinY) * tileSize;
using var sourceImage = SKImage.FromEncodedData(sourceTile.ImageData);
canvas.DrawImage(sourceImage, SKRect.Create(offsetX, offsetY, tileSize, tileSize)); // Source tile scaled to dest rectangle, if needed
}
// Clip and scale to requested size of output image
var geoBBox = EntitiesConverter.MapRectangleToGeographicalBounds(boundingBox);
var pixelOffsetX = WebMercator.LongitudeToPixelXAtZoom(geoBBox.MinLongitude, zoom) - tileSize * tileMinX;
var pixelOffsetY = WebMercator.LatitudeToPixelYAtZoom(geoBBox.MaxLatitude, zoom) - tileSize * tileMinY;
var pixelWidth = WebMercator.LongitudeToPixelXAtZoom(geoBBox.MaxLongitude, zoom) - WebMercator.LongitudeToPixelXAtZoom(geoBBox.MinLongitude, zoom);
var pixelHeight = WebMercator.LatitudeToPixelYAtZoom(geoBBox.MinLatitude, zoom) - WebMercator.LatitudeToPixelYAtZoom(geoBBox.MaxLatitude, zoom);
var sourceRectangle = SKRect.Create((float)pixelOffsetX, (float)pixelOffsetY, (float)pixelWidth, (float)pixelHeight);
var destRectangle = SKRect.Create(0, 0, width, height);
using SKImage canvasImage = surface.Snapshot();
outputCanvas.DrawImage(canvasImage, sourceRectangle, destRectangle, new SKPaint {
FilterQuality = SKFilterQuality.High,
});
}