CRC32 is a great hash to check for large-scale data-corruption, but not to ensure uniqueness - and LibreOffice builds a fair bit of its image comparison foo on the idea that it is unique. A crc32 hash is prone to collisions (due to its small size, any 32-bit hash couldn't be better): it has 1/2 odds to loose an image for ~77000 comparisons: http://preshing.com/20110504/hash-collision-probabilities (so, quite a real number of real documents are expected to suffer). We should use CRC64, or better - though the exact algorithm is fairly immaterial - but having more precision would help, while keeping this a single integer type rather than a more complex wrapper task. Marco is looking into this.
If hashes collide - you loose (one of) your images =)
Michael Meeks committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/core/commit/?id=07254e701fe8cbb7babbfaaf1f096b1afbd5eaf2 tdf#93532 - Bitmap CRC unit tests. It will be available in 5.1.0. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Marco Cecchetti committed a patch related to this issue. It has been pushed to "libreoffice-5-0": http://cgit.freedesktop.org/libreoffice/core/commit/?id=f85ed94f46e9f1b15cb42d66380e666ce7ee71ee&h=libreoffice-5-0 tdf#93532 - Switching to 64-bit checksum It will be available in 5.0.2. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Michael Meeks committed a patch related to this issue. It has been pushed to "libreoffice-5-0": http://cgit.freedesktop.org/libreoffice/core/commit/?id=072f5090e57ddbc2954efafa38b57056a5e52abb&h=libreoffice-5-0 tdf#93532 - Bitmap CRC unit tests. It will be available in 5.0.2. The patch should be included in the daily builds available at http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More information about daily builds can be found at: http://wiki.documentfoundation.org/Testing_Daily_Builds Affected users are encouraged to test the fix and report feedback.
Hello, Is this bug fixed? If so, could you please close it as RESOLVED FIXED?
Yes; a 64bit CRC is now implemented everywhere.