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Bitmap(file) locks the file. #4994

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Merged
merged 2 commits into from
Apr 2, 2020
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Bitmap(file) locks the file. #4994

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849d274
construct new Bitmap(file) locks the underlying file for the lifetime…
ganik Apr 1, 2020
45aeb6c
Maintain original pixel format from file.
ganik Apr 1, 2020
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6 changes: 5 additions & 1 deletion src/Microsoft.ML.ImageAnalytics/ImageLoader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -237,7 +237,11 @@ private Delegate MakeGetterImageDataViewType(DataViewRow input, int iinfo, Func<
if (!string.IsNullOrWhiteSpace(_parent.ImageFolder))
path = Path.Combine(_parent.ImageFolder, path);

dst = new Bitmap(path) { Tag = path };
// to avoid locking file, use the construct below to load bitmap
var bytes = File.ReadAllBytes(path);
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This is interesting. Can you please help me understand why the change was necessary?

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The first change was not preserving the original pixel encoding (format) from the file. It looks like the copy constructor was modifying the format. The second iteration preserves original encoding by moving all the bytes into the byte stream, so only underlying media is changed (memory vs file). See https://stackoverflow.com/questions/4803935/free-file-locked-by-new-bitmapfilepath for more details

var ms = new MemoryStream(bytes);
dst = (Bitmap)Image.FromStream(ms);
dst.Tag = path;

// Check for an incorrect pixel format which indicates the loading failed
if (dst.PixelFormat == System.Drawing.Imaging.PixelFormat.DontCare)
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