benscode-StitcherApi/Services/ImageService.cs

using StitcherApi.Models;
using StitcherApi.Services.Fast;
using StitcherApi.Services.Streaming;
using StitcherApi.Services.Utilities;

namespace StitcherApi.Services;

public class ImageService : IImageService
{
    private readonly ILogger<ImageService> _logger;
    private readonly FastProcessor _fastProcessor;
    private readonly StreamingProcessor _streamingProcessor;

    private const double ASPECT_RATIO_THRESHOLD_TALL = 0.25;
    private const double ASPECT_RATIO_THRESHOLD_WIDE = 8.0;
    private const int TILE_COUNT_THRESHOLD = 30;

    public ImageService(IConfiguration config, ILoggerFactory loggerFactory)
    {
        _logger = loggerFactory.CreateLogger<ImageService>();
        string assetPath =
            config["AssetPath"] ?? throw new InvalidOperationException("AssetPath not configured.");

        _fastProcessor = new FastProcessor(assetPath, loggerFactory.CreateLogger<FastProcessor>());
        _streamingProcessor = new StreamingProcessor(
            assetPath,
            loggerFactory.CreateLogger<StreamingProcessor>()
        );
    }

    public async Task<byte[]> GenerateImageAsync(GenerateImageRequest request)
    {
        (int minRow, int minCol, int maxRow, int maxCol) = CoordinateParser.ParseCanvasRect(
            request.CanvasRect
        );

        int tileGridWidth = maxCol - minCol + 1;
        int tileGridHeight = maxRow - minRow + 1;
        int totalTiles = tileGridWidth * tileGridHeight;

        StitchRequest stitchRequest = CreateStitchRequest(request, minRow, minCol, maxRow, maxCol);

        double aspectRatio = (tileGridHeight > 0) ? (double)tileGridWidth / tileGridHeight : 0;

        if (
            totalTiles > TILE_COUNT_THRESHOLD
            || aspectRatio > ASPECT_RATIO_THRESHOLD_WIDE
            || (aspectRatio > 0 && aspectRatio < ASPECT_RATIO_THRESHOLD_TALL)
        )
        {
            _logger.LogInformation("Large, Tall, or Wide canvas detected. Using fast processor.");
            return await _fastProcessor.ProcessAsync(stitchRequest);
        }
        else
        {
            _logger.LogInformation(
                "Small, block-shaped canvas detected. Using robust streaming processor."
            );
            return await _streamingProcessor.ProcessAsync(stitchRequest);
        }
    }

    private StitchRequest CreateStitchRequest(
        GenerateImageRequest request,
        int minRow,
        int minCol,
        int maxRow,
        int maxCol
    )
    {
        const int TILE_SIZE = 720;
        int stitchedCanvasWidth = (maxCol - minCol + 1) * TILE_SIZE;
        int stitchedCanvasHeight = (maxRow - minRow + 1) * TILE_SIZE;
        int cropX = (int)(request.CropOffset[0] * stitchedCanvasWidth);
        int cropY = (int)(request.CropOffset[1] * stitchedCanvasHeight);
        int cropW = (int)(request.CropSize[0] * stitchedCanvasWidth);
        int cropH = (int)(request.CropSize[1] * stitchedCanvasHeight);
        int startTileCol = minCol + cropX / TILE_SIZE;
        int endTileCol = minCol + (cropX + cropW - 1) / TILE_SIZE;
        int startTileRow = minRow + cropY / TILE_SIZE;
        int endTileRow = minRow + (cropY + cropH - 1) / TILE_SIZE;

        return new StitchRequest(
            minRow,
            minCol,
            startTileRow,
            startTileCol,
            endTileRow,
            endTileCol,
            cropX,
            cropY,
            cropW,
            cropH,
            request.OutputScale
        );
    }
}