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perf(image): remove per-pixel allocs + redundant merged-image copy (MAPCO-11321) #256

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Merged
shimoncohen merged 2 commits into from
Oct 15, 2026
Merged

perf(image): remove per-pixel allocs + redundant merged-image copy (MAPCO-11321) #256

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9944042
perf(image): drop per-pixel allocs in upscale and merged-image copy (…
shimoncohen Aug 4, 2026
34422d9
fix(image): exception-safe disposal of merged tile image (MAPCO-11321)
shimoncohen Oct 14, 2026
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32 changes: 25 additions & 7 deletions MergerLogic/ImageProcessing/TileMerger.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -44,8 +44,16 @@ public TileMerger(ITileScaler tileScaler, ILogger<TileMerger> logger)
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] No images where found return null");
return null;
case 1:
ImageFormatter.RemoveImageDateAttributes(images[0]);
image = images[0];
try
{
ImageFormatter.RemoveImageDateAttributes(image);
}
catch
{
image.Dispose();
throw;
}
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] 1 image found");
break;
default:
Expand All @@ -57,21 +65,31 @@ public TileMerger(ITileScaler tileScaler, ILogger<TileMerger> logger)
}

this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] {imageCollection.Count} where found for merge, start 'imageMagic' merging");
using (var mergedImage = imageCollection.Flatten(MagickColor.FromRgba(0, 0, 0, 0)))
// Flatten returns an image independent of the collection, so it outlives the
// collection's disposal without an extra full-image copy.
IMagickImage<byte> mergedImage = imageCollection.Flatten(MagickColor.FromRgba(0, 0, 0, 0))!;
try
{
ImageFormatter.RemoveImageDateAttributes(mergedImage);

mergedImage.ColorSpace = ColorSpace.sRGB;
mergedImage.ColorType = mergedImage.HasAlpha ? ColorType.TrueColorAlpha : ColorType.TrueColor;
image = new MagickImage(mergedImage);
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] 'imageMagic' merging finished");
}
catch
{
mergedImage.Dispose();
throw;
}
image = mergedImage;
this._logger.LogDebug($"[{MethodBase.GetCurrentMethod()?.Name}] 'imageMagic' merging finished");
}
break;
}

Tile tile = new Tile(targetCoords, image);
image.Dispose();
Tile tile;
using (image)
{
tile = new Tile(targetCoords, image);
}
tile.ConvertToFormat(strategy.ApplyStrategy(tile.Format));
return tile;
}
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8 changes: 6 additions & 2 deletions MergerLogic/ImageProcessing/TileScaler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,12 +85,16 @@ public TileScaler(IMetricsProvider metricsProvider, ILogger<TileScaler> logger)
int maxRowOffset = TILE_SIZE * scaledChannels;
int pixelRowBytes = TILE_SIZE * channels;

// Read the whole source pixel buffer once instead of allocating a byte[] per source pixel.
var srcValues = srcPixels.GetValues()!;
int srcStride = baseImage.Width * channels;

//loop relevant source pixels
for (int i = pixelX; i < maxSrcX; i++)
{
for (int j = pixelY; j < maxSrcY; j++)
{
var srcPixel = srcPixels.GetValue(i, j);
int srcPixelIdx = (j * srcStride) + (i * channels);
var targetXStart = (i - pixelX) * scale;
var targetYStart = (j - pixelY) * scale;
var targetPixelIdxStart = (targetXStart + (TILE_SIZE * targetYStart)) * channels;
Expand All @@ -99,7 +103,7 @@ public TileScaler(IMetricsProvider metricsProvider, ILogger<TileScaler> logger)
for (int pixelRowOffset = 0; pixelRowOffset < maxRowOffset; pixelRowOffset += pixelRowBytes)
{
int pixelIdx = targetPixelIdxStart + pixelColOffset + pixelRowOffset;
srcPixel!.CopyTo(pixels, pixelIdx); //copy all channels
Array.Copy(srcValues, srcPixelIdx, pixels, pixelIdx, channels); //copy all channels
}
}
}
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