Re^5: Mapping function values to colors

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Comment on Re^5: Mapping function values to colors

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Re^6: Mapping function values to colors by gone2015 (Deacon) on Dec 11, 2008 at 15:15 UTC
Indeed. You may, nevertheless, wish to fix the fact that when `$v >= $vmax` both the original and the updated code give `(r= 0 g= 0 b= 0)` cf the expected `(r=255 g=255 b=255)`. As to performance, I ran a little benchmark over 1,000,000 random values -200..+200: s/iter colorRamp1785_u colorRamp1785_2 colorRamp1785_3 colorRamp1785_u 7.26 -- -19% -65% colorRamp1785_2 5.85 24% -- -57% colorRamp1785_3 2.54 186% 130% -- YMMV, of course. (colorRamp1785_3 is, of course, a direct look-up, after normalising $vmin..$vmax to 0..1785.) [Colour reproduction and colour perception being what they are, I imagine there's a cunning way of mapping a linear scale to something which appears linear. I just wish I knew what that was :-(] Update: FWIW the fastest I can make a direct look-up is the code below, which benchmarks: s/iter colorRamp1785_u colorRamp1785_1 colorRamp1785_2 colorRamp1785_d colorRamp1785_u 7.23 -- -8% -20% -67% colorRamp1785_1 6.62 9% -- -13% -64% colorRamp1785_2 5.79 25% 14% -- -59% colorRamp1785_d 2.37 205% 179% 144% -- Read more... colorRamp_d (2 kB)	[reply] [d/l] [select]

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Re^6: Mapping function values to colors
by gone2015 (Deacon) on Dec 11, 2008 at 15:15 UTC

Indeed.

You may, nevertheless, wish to fix the fact that when $v >= $vmax both the original and the updated code give (r= 0 g= 0 b= 0) cf the expected (r=255 g=255 b=255).

As to performance, I ran a little benchmark over 1,000,000 random values -200..+200:

                  s/iter colorRamp1785_u colorRamp1785_2 colorRamp1785_3
  colorRamp1785_u   7.26              --            -19%            -65%
  colorRamp1785_2   5.85             24%              --            -57%
  colorRamp1785_3   2.54            186%            130%              --

[Colour reproduction and colour perception being what they are, I imagine there's a cunning way of mapping a linear scale to something which appears linear. I just wish I knew what that was :-(]

Update: FWIW the fastest I can make a direct look-up is the code below, which benchmarks:

                s/iter colorRamp1785_u colorRamp1785_1 colorRamp1785_2 colorRamp1785_d
colorRamp1785_u   7.23              --             -8%            -20%            -67%
colorRamp1785_1   6.62              9%              --            -13%            -64%
colorRamp1785_2   5.79             25%             14%              --            -59%
colorRamp1785_d   2.37            205%            179%            144%              --