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| author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2018-03-05 01:09:39 +0000 |
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| committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2018-03-05 01:09:39 +0000 |
| commit | ffcb1453bce751e315fb422f667e2e61a1137d40 (patch) | |
| tree | 9f36f4f4571a5f0676e222632831d6a9c12f40eb /lib/ppm.h | |
| parent | c13514b9e889dad5a35adc71a29840c206b0a286 (diff) | |
| download | netpbm-mirror-ffcb1453bce751e315fb422f667e2e61a1137d40.tar.gz netpbm-mirror-ffcb1453bce751e315fb422f667e2e61a1137d40.tar.xz netpbm-mirror-ffcb1453bce751e315fb422f667e2e61a1137d40.zip | |
clarify applicable standard, add more precision
git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@3164 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'lib/ppm.h')
| -rw-r--r-- | lib/ppm.h | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/lib/ppm.h b/lib/ppm.h index 5b94af9e..6f1f21b5 100644 --- a/lib/ppm.h +++ b/lib/ppm.h @@ -211,9 +211,7 @@ PPM_DISTANCE(pixel const p1, combination of intensities, whereas luma is a linear combination of gamma-adjusted intensities, as you would find in a Netpbm image. - These are from ITU-R BT.601.5. That means they probably aren't technically - right for use with PPM images, because the PPM spec says ITU-R BT.709. - The two are similar, though. + These are from ITU-R BT.601.5. */ #define PPM_LUMINR (0.2989) #define PPM_LUMING (0.5866) @@ -222,12 +220,12 @@ PPM_DISTANCE(pixel const p1, #define PPM_LUMIN(p) ( PPM_LUMINR * PPM_GETR(p) \ + PPM_LUMING * PPM_GETG(p) \ + PPM_LUMINB * PPM_GETB(p) ) -#define PPM_CHROM_B(p) ( -0.16874 * PPM_GETR(p) \ - - 0.33126 * PPM_GETG(p) \ +#define PPM_CHROM_B(p) ( -0.168736 * PPM_GETR(p) \ + - 0.331264 * PPM_GETG(p) \ + 0.5 * PPM_GETB(p) ) #define PPM_CHROM_R(p) ( 0.5 * PPM_GETR(p) \ - - 0.41869 * PPM_GETG(p) \ - - 0.08131 * PPM_GETB(p) ) + - 0.418688 * PPM_GETG(p) \ + - 0.081312 * PPM_GETB(p) ) pixel ppm_color_from_ycbcr(unsigned int const y, |