Issue 55170 - Allow fast and nicer looking JPEG preview
Summary: Allow fast and nicer looking JPEG preview
Alias: None
Product: gsl
Classification: Code
Component: code (show other issues)
Version: OOo 2.0
Hardware: All All
: P4 Trivial (vote)
Target Milestone: OOo 2.1
Assignee: wolframgarten
QA Contact: issues@gsl
Depends on:
Blocks: 68712
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Reported: 2005-09-28 11:31 UTC by
Modified: 2006-09-14 14:25 UTC (History)
4 users (show)

See Also:
Latest Confirmation in: ---
Developer Difficulty: ---


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Description 2005-09-28 11:31:15 UTC
There are a lot of tasks in OOo that only require JPEGs in preview quality.
Currently previews in OOo are done by loading the entire image and then scaling
it down by using selected pixels of the full image. By using only the
low-frequency coefficients of the JPEG block's DCT there would be these benefits:
- less memory usage
  - by not needing the memory for the full blown images
- increased speed by
  - not needing complete IDCT
  - avoiding color transforms on pixels that will get ignored later
  - less work for Image->UniqueHash operations
- better preview quality
  - because the image is not disturbed by aliasing issues between high-frequency
    DCT coefficients and the statistical downsampling
Comment 1 2005-09-28 11:32:18 UTC
Comment 2 2005-09-28 11:35:07 UTC
Comment 3 thb 2005-10-04 11:34:42 UTC
Added myself to cc list.
Comment 4 wolframgarten 2005-12-14 12:33:18 UTC
WG: target set because CWS target is delayed.
Comment 5 2006-07-12 14:51:05 UTC
Fixed in CWS pngperf
Comment 6 2006-08-24 13:52:28 UTC
Reopening for reassignment to QA.
Comment 7 2006-08-24 13:52:59 UTC
Comment 8 2006-08-24 13:53:22 UTC
Please verify in CWS pngperf.
Comment 9 wolframgarten 2006-08-28 13:55:21 UTC
Comment 10 wolframgarten 2006-09-14 14:25:58 UTC