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author | pacman <pacman@b3059339-0415-0410-9bf9-f77b7e298cf2> | 2006-02-24 22:18:45 +0000 |
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committer | pacman <pacman@b3059339-0415-0410-9bf9-f77b7e298cf2> | 2006-02-24 22:18:45 +0000 |
commit | c8610ae9e29d12aadd436203336c4d8ec85415d6 (patch) | |
tree | f423ccb4f827b14910863ab99d8cb2e9679ad1bb /DOCS/tech | |
parent | 469dda5b0a037906b95e71b585d6b1a62c0a9552 (diff) | |
download | mpv-c8610ae9e29d12aadd436203336c4d8ec85415d6.tar.bz2 mpv-c8610ae9e29d12aadd436203336c4d8ec85415d6.tar.xz |
Add a practical description of endian-independent RGB/BGR coding
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@17681 b3059339-0415-0410-9bf9-f77b7e298cf2
Diffstat (limited to 'DOCS/tech')
-rw-r--r-- | DOCS/tech/colorspaces.txt | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/DOCS/tech/colorspaces.txt b/DOCS/tech/colorspaces.txt index f4a1f88c2a..dc00fd388d 100644 --- a/DOCS/tech/colorspaces.txt +++ b/DOCS/tech/colorspaces.txt @@ -135,3 +135,24 @@ that you actually get: Depending upon the CPU being little- or big-endian, different 'in memory' and 'in register' formats will be equal (LE -> BGRA == BGR32 / BE -> ARGB == BGR32) + +Practical coding guide: + +The 4, 8, 15, and 16 bit formats are defined so that the portable way to +access them is to load the pixel into an integer and use bitmasks. + +The 24 bit formats are defined so that the portable way to access them is +to address the 3 components as separate bytes, as in ((uint8_t *)pixel)[0], +((uint8_t *)pixel)[1], ((uint8_t *)pixel)[2]. + +When a 32-bit format is identified by the four characters A, R, G, and B in +some order, the portable way to access it is by addressing the 4 components +as separate bytes. + +When a 32-bit format is identified by the 3 characters R, G, and B in some +order followed by the number 32, the portable way to access it is to load +the pixel into an integer and use bitmasks. + +When the above portable access methods are not used, you will need to write +2 versions of your code, and use #ifdef WORDS_BIGENDIAN to choose the correct +one. |