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Work around Chrome bug with JPEG rotation information being lost after image is cloned #35

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robertknight opened this issue Jun 4, 2022 · 0 comments · Fixed by #36
Closed

Work around Chrome bug with JPEG rotation information being lost after image is cloned #35

robertknight opened this issue Jun 4, 2022 · 0 comments · Fixed by #36

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@robertknight
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This project needs to work around an issue where the EXIF rotation information from the input image in Chrome is lost when the ImageBitmap is transferred to a background thread by OCRClient for processing. See https://bugs.chromium.org/p/chromium/issues/detail?id=1332947.
robertknight added a commit that referenced this issue Jun 4, 2022
@robertknight
Convert ImageBitmap => ImageData on the main thread in all browsers
4b630f7 
Chrome has a bug where image orientation metadata in JPEG images is lost
when an ImageBitmap is cloned via a structured clone [1]. Therefore we have
to do ImageBitmap => ImageData conversion on the main thread to ensure
that the OCR engine receives decoded image data which respects the image
orientation.

Prior to this fix the rendered image orientation and the OCR output did
not match up in Chrome if the input image was rotated.

Since neither Firefox nor Safari support OffscreenCanvas, this means
that all browsers are now doing ImageBitmap => ImageData conversion on
the main thread.

Fixes #35

[1] https://bugs.chromium.org/p/chromium/issues/detail?id=1332947
robertknight added a commit that referenced this issue Jun 4, 2022
@robertknight
Convert ImageBitmap => ImageData on the main thread in all browsers
c5a8592 
Chrome has a bug where image orientation metadata in JPEG images is lost
when an ImageBitmap is cloned via a structured clone [1]. Therefore we have
to do ImageBitmap => ImageData conversion on the main thread to ensure
that the OCR engine receives decoded image data which respects the image
orientation.

Prior to this fix the rendered image orientation and the OCR output did
not match up in Chrome if the input image was rotated.

Since neither Firefox nor Safari support OffscreenCanvas, this means
that all browsers are now doing ImageBitmap => ImageData conversion on
the main thread.

Fixes #35

[1] https://bugs.chromium.org/p/chromium/issues/detail?id=1332947
@robertknight robertknight mentioned this issue Jun 4, 2022
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Convert ImageBitmap => ImageData on the main thread in all browsers robertknight/tesseract-wasm
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@robertknight