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Always prefer the PDF.js JPEG decoder for very large images, in order to reduce peak memory usage (issue 11694) #11707

Merged
merged 1 commit into from
Mar 24, 2020
Merged

Always prefer the PDF.js JPEG decoder for very large images, in order to reduce peak memory usage (issue 11694) #11707

merged 1 commit into from
Mar 24, 2020

Commits on Mar 20, 2020

  1. Always prefer the PDF.js JPEG decoder for very large images, in order… 

    … to reduce peak memory usage (issue 11694)

When JPEG images are decoded by the browser, on the main-thread, there's a handful of short-lived copies of the image data; see https://github.com/mozilla/pdf.js/blob/c3f4690bde8137d80c74203b1ad91476fc2ca160/src/display/api.js#L2364-L2408
That code thus becomes quite problematic for very big JPEG images, since it increases peak memory usage a lot during decoding. In the referenced issue there's a couple of JPEG images whose dimensions are `10006 x 7088` (i.e. ~68 mega-pixels), which causes the *peak* memory usage to increase by close to `1 GB` (i.e. one giga-byte) in my testing.

By letting the PDF.js JPEG decoder, rather than the browser, handle very large images the *peak* memory usage is considerably reduced and the allocated memory also seem to be reclaimed faster.

*Please note:* This will lead to movement in some existing `eq` tests.
    @Snuffleupagus
    Snuffleupagus committed Mar 20, 2020
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